Physics and Astronomy › Astronomy and Astrophysics

Stellar, planetary, and galactic studies

Works Count: 192467

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This cluster of papers covers a wide range of topics in stellar astrophysics, including the study of exoplanets, galactic evolution, stellar and planetary system formation, and the exploration of the Milky Way. It encompasses research on massive stars, planetary systems around different types of stars, and the utilization of data from missions like Gaia and Kepler for understanding the properties and dynamics of celestial objects.

Keywords

Stellar Astrophysics; Exoplanets; Galactic Evolution; Stellar Evolution; Milky Way; Gaia Mission; Planetary Systems; Massive Stars; Astronomical Surveys; Astrophysical Spectroscopy

TheGaiamission

2016-09-15

T. Prusti , J. H. J. de Bruijne , A. G. A. Brown +7 more

Gaia is a cornerstone mission in the science programme of the EuropeanSpace Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept … Gaia is a cornerstone mission in the science programme of the EuropeanSpace Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

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Stellar Structure and Evolution

2012-01-01

Rudolf Kippenhahn , Alfred Weigert , A. Weiß

A Jupiter-mass companion to a solar-type star

1995-11-01

M. Mayor , D. Queloz

The Rate of Star Formation.

1959-03-01

Maarten Schmidt

Search Bar to Enter New Query quick field: Author First Author Abstract Year Fulltext Select a field or operator abstract abstract only acknowledgements affiliation arXiv category author count author bibcode … Search Bar to Enter New Query quick field: Author First Author Abstract Year Fulltext Select a field or operator abstract abstract only acknowledgements affiliation arXiv category author count author bibcode bibliographic group bib abbrev, e.g. ApJ body of article data archive collection citation count doctype doi entdate first author fulltext identifier inst keyword object orcid page property publication full name date published title volume year citations() pos() references() reviews() similar() topn() trending() useful() single wildcard: ? wildcard: * exact match: = All Search Terms Your search returned 0 results Your search returned 0 results

The interstellar extinction law from 1 to 13 microns

1985-01-01

G. H. Rieke , M. J. Lebofsky

view Abstract Citations (2581) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The interstellar extinction law from 1 to 13 microns. Rieke, G. H. ; Lebofsky, … view Abstract Citations (2581) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The interstellar extinction law from 1 to 13 microns. Rieke, G. H. ; Lebofsky, M. J. Abstract Measurements from 1 to 13 μm are reported for ο Sco and for stars in the galactic center. The interstellar extinction law toward these sources and toward VI Cyg No. 12 is the same from 1 to 13 μm. An improved estimate of the extinction law beyond 3 μm is presented, including an improved ratio of total to selective extinction, R ≈ 3.09±0.03, and an improved ratio of total extinction to optical depth in the 10 μm silicate absorption, Av/τSi = 16.6±2.1. Publication: The Astrophysical Journal Pub Date: January 1985 DOI: 10.1086/162827 Bibcode: 1985ApJ...288..618R Keywords: Galactic Nuclei; Infrared Astronomy; Interstellar Extinction; Interstellar Matter; Molecular Clouds; Astrophysics full text sources ADS | data products SIMBAD (6)

Evolutionary population synthesis: models, analysis of the ingredients and application to high-z galaxies

2005-08-25

Claudia Maraston

Evolutionary population synthesis models for a wide range of metallicities, ages, star formation histories, and Horizontal Branch morphologies, including blue morphologies at high metallicity, are computed. The energetics of the … Evolutionary population synthesis models for a wide range of metallicities, ages, star formation histories, and Horizontal Branch morphologies, including blue morphologies at high metallicity, are computed. The energetics of the post Main Sequence evolutionary phases are evaluated with the fuel consumption theorem. The impact on the models of the stellar evolutionary tracks is assessed. We find modest differences in synthetic broad-band colours as induced by the use of different tracks in our code (e.g. d(V-K) ~ 0.08 mag; d(B-V) ~ 0.03 mag). These differences are smaller than the scatter among other models in the literature, even when the latter adopt the same evolutionary tracks. The models are calibrated with globular cluster data from the Milky Way for old ages, and the Magellanic Clouds plus the merger remnant galaxy NGC 7252, for ages of ~ 0.1 - 2 Gyr, in a large wavelength range from U to K. Particular emphasis is put on the contribution from the Thermally-Pulsing Asymptotic Giant Branch phase. We show that this phase is crucial for the modelling of young stellar populations by the comparison with observed spectral energy distributions of Magellanic Clouds clusters, which are characterised by high fluxes both blueward and redward the V-band. We find that the combination of the near-IR spectral indices C2 and H2O can be used to determine the metallicity of ~ 1 Gyr stellar populations. We re-analyze the spectral energy distributions of some of the high-z galaxies (2.4 < z < 2.9) observed with the Spitzer Space Telescope by Yan et al. (2004). Their high rest-frame near-IR fluxes are reproduced very well with the models including Thermally-Pulsing Asymptotic Giant Branch stars for ages in the range 0.6-1.5 Gyr, suggesting formation redshifts around z ~ 3-6.

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Astrophysics of Gaseous Nebulae and Active Galactic Nuclei

1989-10-01

Donald E. Osterbrock , J. Michael Shull

Photoionization equilibrium thermal equilibrium calculation of emitted spectrum comparison of theory with observations internal dynamics of gaseous nebulae interstellar dust H II regions in the galactic context planetary nebulae nova … Photoionization equilibrium thermal equilibrium calculation of emitted spectrum comparison of theory with observations internal dynamics of gaseous nebulae interstellar dust H II regions in the galactic context planetary nebulae nova and supernova remnants active galactic nuclei - diagnostic and physics active galactic nuclei - results.

Stellar population synthesis at the resolution of 2003

2003-09-22

Gustavo Bruzual , S. Charlot

We present a new model for computing the spectral evolution of stellar populations at ages between 100,000 yr and 20 Gyr at a resolution of 3 A across the whole … We present a new model for computing the spectral evolution of stellar populations at ages between 100,000 yr and 20 Gyr at a resolution of 3 A across the whole wavelength range from 3200 to 9500 A for a wide range of metallicities. These predictions are based on a newly available library of observed stellar spectra. We also compute the spectral evolution across a larger wavelength range, from 91 A to 160 micron, at lower resolution. The model incorporates recent progress in stellar evolution theory and an observationally motivated prescription for thermally-pulsing stars on the asymptotic giant branch. The latter is supported by observations of surface brightness fluctuations in nearby stellar populations. We show that this model reproduces well the observed optical and near-infrared colour-magnitude diagrams of Galactic star clusters of various ages and metallicities. Stochastic fluctuations in the numbers of stars in different evolutionary phases can account for the full range of observed integrated colours of star clusters in the Magellanic Clouds. The model reproduces in detail typical galaxy spectra from the Early Data Release (EDR) of the Sloan Digital Sky Survey (SDSS). We exemplify how this type of spectral fit can constrain physical parameters such as the star formation history, metallicity and dust content of galaxies. Our model is the first to enable accurate studies of absorption-line strengths in galaxies containing stars over the full range of ages. Using the highest-quality spectra of the SDSS EDR, we show that this model can reproduce simultaneously the observed strengths of those Lick indices that do not depend strongly on element abundance ratios [abridged].

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MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): PLANETS, OSCILLATIONS, ROTATION, AND MASSIVE STARS

2013-08-28

Bill Paxton , Matteo Cantiello , Phil Arras +7 more

We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESAstar. Improvements in MESAstar's ability to … We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESAstar. Improvements in MESAstar's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESAstar. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESAstar calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3–8 M☉ stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable calculations of rotating-star models, which we compare thoroughly with earlier work. We introduce a new treatment of radiation-dominated envelopes that allows the uninterrupted evolution of massive stars to core collapse. This enables the generation of new sets of supernovae, long gamma-ray burst, and pair-instability progenitor models. We substantially modify the way in which MESAstar solves the fully coupled stellar structure and composition equations, and we show how this has improved the scaling of MESA's calculational speed on multi-core processors. Updates to the modules for equation of state, opacity, nuclear reaction rates, and atmospheric boundary conditions are also provided. We describe the MESA Software Development Kit that packages all the required components needed to form a unified, maintained, and well-validated build environment for MESA. We also highlight a few tools developed by the community for rapid visualization of MESAstar results.

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The Luminosity Function and Stellar Evolution.

1955-01-01

E. E. Salpeter

view Abstract Citations (7566) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Luminosity Function and Stellar Evolution. Salpeter, Edwin E. Abstract The evolutionary significance of … view Abstract Citations (7566) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Luminosity Function and Stellar Evolution. Salpeter, Edwin E. Abstract The evolutionary significance of the observed luminosity function for main-sequence stars in the solar neighborhood is discussed. The hypothesis is made that stars move off the main sequence after burning about 10 per cent of their hydrogen mass and that stars have been created at a uniform rate in the solar neighborhood for the last five billion years. Using this hypothesis and the observed luminosity function, the rate of star creation as a function of stellar mass is calculated. The total number and mass of stars which have moved off the main sequence is found to be comparable with the total number of white dwarfs and with the total mass of all fainter main-sequence stars, respectively. Publication: The Astrophysical Journal Pub Date: January 1955 DOI: 10.1086/145971 Bibcode: 1955ApJ...121..161S full text sources ADS |

The structure of star clusters. I. an empirical density law

1962-10-01

Ivan R. King

New observations make it possible to re-examine the question of the density distribution in globular clusters. Jeans' law is based on insufficient observations and on an incorrect theory. On Palomar … New observations make it possible to re-examine the question of the density distribution in globular clusters. Jeans' law is based on insufficient observations and on an incorrect theory. On Palomar Schmidt plates the densities can be followed far enough out to define a limit to a globular cluster. The observed loca- tion of this limit agrees with the limit to be expected as a result of galactic tidal forces. The central regions of all globular clusters are similar, except for the effect of the tidal cutoff. An empirical formula has been found that represents the density from center to edge in globular clusters of all degrees of central concen- tration. The formula has three parameters, which is the minimum number permitted by the physical circum- stances. Globular clusters are therefore as similar in structure as they could possibly be. Galactic clusters and Sculptor-type dwarf galaxies also appear to follow the same density law. From dynamical considerations it would appear that all these stellar systems are subject to two types of relaxation, which produce nearly identical effects. The first relaxation is produced by the initial mixing of the system. Thereupon stellar encounters slowly change the density parameters without affecting the basic law. Relative to globular clusters, giant elliptical galaxies have an excess of brightness near the center. This difference can be explained as a result of relaxation, equipartition, and an excess of dwarf stars.

JHKLM photometry - Standard systems, passbands, and intrinsic colors

1988-09-01

M. S. Bessell , J. M. Brett

The relations between colors of the JHKL systems of several observatories are examined, and linear relations are derived for transformation between the (J-K), (J-H), (H-K), and (K-L) colors in the … The relations between colors of the JHKL systems of several observatories are examined, and linear relations are derived for transformation between the (J-K), (J-H), (H-K), and (K-L) colors in the different systems. A homogenized system is proposed, based on the systems of Glass (1984) and Johnson et al. (1966). The homogenized data sets are used to derive intrinsic colors for a number of giants and dwarfs. The passbands of several IR systems are estimated and the synthetic colors of the systems are compared using blackbody and stellar fluxes. The passbands were adjusted in wavelength to produce agreement with observed relations between different systems, making it possible to estimate the effective wavelengths of the different natural systems.

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Analytic Light Curves for Planetary Transit Searches

2002-12-01

Kaisey S. Mandel , Eric Agol

We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth … We present exact analytic formulae for the eclipse of a star described by quadratic or nonlinear limb darkening. In the limit that the planet radius is less than a tenth of the stellar radius, we show that the exact light curve can be well approximated by assuming the region of the star blocked by the planet has constant surface brightness. We apply these results to the Hubble Space Telescope observations of HD 209458, showing that the ratio of the planetary to stellar radii is 0.1207 ± 0.0003. These formulae give a fast and accurate means of computing light curves using limb-darkening coefficients from model atmospheres that should aid in the detection, simulation, and parameter fitting of planetary transits.

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MEASURING REDDENING WITH SLOAN DIGITAL SKY SURVEY STELLAR SPECTRA AND RECALIBRATING SFD

2011-08-08

Edward F. Schlafly , Douglas P. Finkbeiner

We present measurements of dust reddening using the colors of stars with spectra in the Sloan Digital Sky Survey. We measure reddening as the difference between the measured and predicted … We present measurements of dust reddening using the colors of stars with spectra in the Sloan Digital Sky Survey. We measure reddening as the difference between the measured and predicted colors of a star, as derived from stellar parameters from the Sloan Extension for Galactic Understanding and Exploration Stellar Parameter Pipeline. We achieve uncertainties of 56, 34, 25, and 29 mmag in the colors u − g, g − r, r − i, and i − z, per star, though the uncertainty varies depending on the stellar type and the magnitude of the star. The spectrum-based reddening measurements confirm our earlier "blue tip" reddening measurements, finding reddening coefficients different by −3%, 1%, 1%, and 2% in u − g, g − r, r − i, and i − z from those found by the blue tip method, after removing a 4% normalization difference. These results prefer an RV = 3.1 Fitzpatrick reddening law to O'Donnell or Cardelli et al. reddening laws. We provide a table of conversion coefficients from the Schlegel et al. (SFD) maps of E(B − V) to extinction in 88 bandpasses for four values of RV, using this reddening law and the 14% recalibration of SFD first reported by Schlafly et al. and confirmed in this work.

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On the gravitational stability of a disk of stars

1964-05-01

Alar Toomre

view Abstract Citations (3063) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the gravitational stability of a disk of stars. Toomre, A. Abstract This paper … view Abstract Citations (3063) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the gravitational stability of a disk of stars. Toomre, A. Abstract This paper considers the question of the large-scale gravitational stability of an arbitrary, highly flattened stellar system, which is assumed initially to rotate in approximate equilibrium between its self-gravitation and the centrifugal forces. It is concluded that no such disk, if fairly smooth or uniform, can be entirely stable against a tendency to form massive condensations within its own plane, unless the root-mean-square random velocities of its constituents, in the directions parallel to that plane, are everywhere sufficiently large. Lacking such random motions, it is shown that the system must be vulnerable to numerous unstable disturbances, the dimensions of which may approach its over-all radius, and whose times of growth are to be reckoned in fractions of the typical periods of revolution. The minimum root-mean-square radial velocity dispersion required in any one vicinity for the complete suppression of all axisymmetric instabilities is calculated (in collaboration with A. Kalnajs) as 3.36 G /K, where G is the gravitational constant, and and K are the local values of the projected stellar density and the epicyclic frequency, respectively. From that, and the observed j# and K, together with their uncertainties, this minimum for the solar neighborhood of our Galaxy is estimated to fall between 20 and 35 k /sec, a range which indeed encompasses the actual radial velocity dispersions of the most predominant types of stars in our vicinity. It is pointed out that both this curious agreement, and also the well-known discrepancy between the z- and r-velocity dispersions at least of the older disk stars, may be explainable in terms of past instabilities of this galactic disk. Publication: The Astrophysical Journal Pub Date: May 1964 DOI: 10.1086/147861 Bibcode: 1964ApJ...139.1217T full text sources ADS |

Habitable Zones around Main Sequence Stars

1993-01-01

James F. Kasting , D. P. Whitmire , R. T. Reynolds

Realization of Accurate Close-Binary Light Curves: Application to MR Cygni

1971-06-01

R. E. Wilson , E. J. Devinney

view Abstract Citations (2530) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Realization of Accurate Close-Binary Light Curves: Application to MR Cygni Wilson, Robert E. ; … view Abstract Citations (2530) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Realization of Accurate Close-Binary Light Curves: Application to MR Cygni Wilson, Robert E. ; Devinney, Edward J. Abstract A general procedure for computing monochromatic light curves of close eclipsing-binary systems is presented, with allowance for rotational and tidal distortion, the reflection effect, limb darkening, and gravity darkening. All basic techniques used to compute light curves are specified. Solution of the inverse problem (finding the elements from observations) is accomplished by differential corrections, and probable errors are obtained for all adjustable parameters. No rectification of any kind is used or needed. Because of the basic flexibility of the scheme, present limitations (e.g., synchronous rotation only, black- body physics) may be improved upon with reasonable convenience, as time permits. The procedure has been applied to B and V observations of MR Cyg, and the results of the differential corrections adjustments are given. With the use of available spectroscopic observations and model-atmosphere results by Mihalas, the components are placed in the H-R diagram. Although the primary seems to be on the main sequence, the secondary is found to be above the main sequence an observation which suggests that the secondary may still be in the gravitational-con traction phase. Publication: The Astrophysical Journal Pub Date: June 1971 DOI: 10.1086/150986 Bibcode: 1971ApJ...166..605W full text sources ADS | data products SIMBAD (1) Related Materials (5) Addendum: 1972ApJ...171..413W Described in: 1979ApJ...234.1054W Described in: 1990ApJ...356..613W Described in: 2008ApJ...672..575W Source Software: 2020ascl.soft04004W

Double white dwarfs as progenitors of R Coronae Borealis stars and Type I supernovae

1984-02-01

R. F. Webbink

view Abstract Citations (1980) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Double white dwarfs as progenitors of R Coronae Borealis stars and type I supernovae. … view Abstract Citations (1980) References (46) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Double white dwarfs as progenitors of R Coronae Borealis stars and type I supernovae. Webbink, R. F. Abstract Tidal mass transfer in double degenerate systems is explored. The sequence of double white dwarfs divides naturally into three segments: (1) low-mass helium/helium pairs are unstable to dynamical time-scale mass transfer and probably coalesce to form helium-burning sdO stars; (2) in helium/carbon-oxygen pairs, mass transfer occurs on the time scale for gravitational radiation losses; the accreted helium is quickly ignited, and the accretor expands to dimensions characteristic of R CrB stars, engulfing its companion star; and (3) carbon-oxygen/carbon-oxygen pairs are again unstable to dynamical time-scale mass transfer and, since their total masses exceed the Chandrasekhar limit, are destined to become supernovae. Inactive lifetimes in these latter systems between creation and interaction can exceed 10 billion years. Birthrates of R CrB stars and Type I supernovae by evolution of double white dwarfs are in reasonable agreement with observational estimates. Publication: The Astrophysical Journal Pub Date: February 1984 DOI: 10.1086/161701 Bibcode: 1984ApJ...277..355W Keywords: Binary Stars; Corona Borealis Constellation; R Coronae Borealis Stars; Stellar Evolution; Supernovae; White Dwarf Stars; B Stars; Carbon Stars; Chandrasekhar Equation; O Stars; Stellar Mass Accretion; Stellar Mass Ejection; Astrophysics full text sources ADS | data products SIMBAD (2)

The structure of star clusters. III. Some simple dvriamical models

1966-02-01

Ivan R. King

Dynamical models of star clusters are presented, based on steady-state solutions of the Fokker-Planck equation. The models are spatially limited, corresponding to the tidal cutoff imposed by the Milky Way. … Dynamical models of star clusters are presented, based on steady-state solutions of the Fokker-Planck equation. The models are spatially limited, corresponding to the tidal cutoff imposed by the Milky Way. Their projected density distributions are similar to those observed in open clusters, globular clusters, and elliptical galaxies. Within each model the fractional escape rate is uniform throughout. The escape rate from a cluster depends on the number of stars and the strength of the tidal force field; when expressed in this way it is almost independent of core radius or central concentration. Quantitative application to actual clusters must await a discussion of models containing a realistic stellar mixture.

THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE): MISSION DESCRIPTION AND INITIAL ON-ORBIT PERFORMANCE

2010-11-09

E. L. Wright , Peter Eisenhardt , Amy Mainzer +7 more

The all sky surveys done by the Palomar Observatory Schmidt, the European Southern Observatory Schmidt, and the United Kingdom Schmidt, the InfraRed Astronomical Satellite, and the Two Micron All Sky … The all sky surveys done by the Palomar Observatory Schmidt, the European Southern Observatory Schmidt, and the United Kingdom Schmidt, the InfraRed Astronomical Satellite, and the Two Micron All Sky Survey have proven to be extremely useful tools for astronomy with value that lasts for decades. The Wide-field Infrared Survey Explorer (WISE) is mapping the whole sky following its launch on 2009 December 14. WISE began surveying the sky on 2010 January 14 and completed its first full coverage of the sky on July 17. The survey will continue to cover the sky a second time until the cryogen is exhausted (anticipated in 2010 November). WISE is achieving 5σ point source sensitivities better than 0.08, 0.11, 1, and 6 mJy in unconfused regions on the ecliptic in bands centered at wavelengths of 3.4, 4.6, 12, and 22 μm. Sensitivity improves toward the ecliptic poles due to denser coverage and lower zodiacal background. The angular resolution is 61, 64, 65, and 120 at 3.4, 4.6, 12, and 22 μm, and the astrometric precision for high signal-to-noise sources is better than 015.

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Evolution of binary stars and the effect of tides on binary populations

2002-02-01

Jarrod R. Hurley , Christopher A. Tout , Onno R. Pols

We present a rapid binary-evolution algorithm that enables modelling of even the most complex binary systems. In addition to all aspects of single-star evolution, features such as mass transfer, mass … We present a rapid binary-evolution algorithm that enables modelling of even the most complex binary systems. In addition to all aspects of single-star evolution, features such as mass transfer, mass accretion, common-envelope evolution, collisions, supernova kicks and angular momentum loss mechanisms are included. In particular, circularization and synchronization of the orbit by tidal interactions are calculated for convective, radiative and degenerate damping mechanisms. We use this algorithm to study the formation and evolution of various binary systems. We also investigate the effect that tidal friction has on the outcome of binary evolution. Using the rapid binary code, we generate a series of large binary populations and evaluate the formation rate of interesting individual species and events. By comparing the results for populations with and without tidal friction, we quantify the hitherto ignored systematic effect of tides and show that modelling of tidal evolution in binary systems is necessary in order to draw accurate conclusions from population synthesis work. Tidal synchronism is important but, because orbits generally circularize before Roche lobe overflow, the outcome of the interactions of systems with the same semilatus rectum is almost independent of eccentricity. It is not necessary to include a distribution of eccentricities in population synthesis of interacting binaries; however, the initial separations should be distributed according to the observed distribution of semilatera recta rather than periods or semimajor axes.

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A Catalog of Parameters for Globular Clusters in the Milky Way

1996-10-01

William E. Harris

A database of parameters for globular star clusters in the Milky Way is described which is available in electronic form through the WorldWideWeb. The information in the catalog includes up-to-date … A database of parameters for globular star clusters in the Milky Way is described which is available in electronic form through the WorldWideWeb. The information in the catalog includes up-to-date measurements for cluster distance, reddening, luminosity, colors and spectral types, velocity, structural and dynamical parameters, horizontal branch morphology, metallicity, and other quantities. This catalog will be updated regularly and maintained in electronic form for widest possible accessibility.

Kepler Planet-Detection Mission: Introduction and First Results

2010-01-08

W. J. Borucki , David Koch , Gibor Basri +7 more

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures … The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

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Secondary standard stars for absolute spectrophotometry

1983-03-01

J. B. Oke , James E. Gunn

view Abstract Citations (2379) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Secondary standard stars for absolute spectrophotometry. Oke, J. B. ; Gunn, J. E. Abstract … view Abstract Citations (2379) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Secondary standard stars for absolute spectrophotometry. Oke, J. B. ; Gunn, J. E. Abstract Based on an adopted absolute spectral energy distribution for the primary standard star Alpha Lyrae, absolute fluxes are given for the four very metal-deficient F type subdwarfs HD 19445, HD 84937, BD + 26.2606 deg, and BD + 17.4703 deg. Somewhat inferior data are also given for HD 140283. The data are given for 40-A bands and cover the wavelength range from 3080 A to 12,000 A. The four stars, all near magnitude 9 and distributed around the sky, are intended as secondary standards for absolute spectrophotometry. Publication: The Astrophysical Journal Pub Date: March 1983 DOI: 10.1086/160817 Bibcode: 1983ApJ...266..713O Keywords: Reference Stars; Spectral Energy Distribution; Stellar Spectrophotometry; Subdwarf Stars; Calibrating; Line Spectra; Astronomy full text sources ADS | data products SIMBAD (5)

Time Scales for CA II Emission Decay, Rotational Braking, and Lithium Depletion

1972-02-01

A. Skumanich

view Abstract Citations (1668) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time Scales for Ca II Emission Decay, Rotational Braking, and Lithium Depletion Skumanich, A. … view Abstract Citations (1668) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time Scales for Ca II Emission Decay, Rotational Braking, and Lithium Depletion Skumanich, A. Abstract A comparison of the Ca+ emission luminosity-after correction for spectral-type effects-for the Pleiades, Ursa Major, and Hyades stars and the Sun indicate an emission decay which varies as the inverse square root of the age. Further, the rotational decay curve is found to satisfy the same law. It is further suggested that lithium depletion follows the same law but only as far as the Hyades age, after which the depletion proceeds exponentially. Since Ca+ emission is linearly proportional to magnetic field strength at the surface, one can predict that the surface fields are proportional to angular velocity and decay as the inverse square root. The above results are predicated Qi' the standard Hyades age (0.4 billion years). Publication: The Astrophysical Journal Pub Date: February 1972 DOI: 10.1086/151310 Bibcode: 1972ApJ...171..565S full text sources ADS | data products SIMBAD (4)

A synthetic view on structure and evolution of the Milky Way

2003-09-24

A. C. Robin , C. Reylé , S. Derrière +1 more

Since the Hipparcos mission and recent large scale surveys in the optical and the near-infrared, new constraints have been obtained on the structure and evolution history of the Milky Way. … Since the Hipparcos mission and recent large scale surveys in the optical and the near-infrared, new constraints have been obtained on the structure and evolution history of the Milky Way. The population synthesis approach is a useful tool to interpret such data sets and to test scenarios of evolution of the Galaxy. We present here new constraints on evolution parameters obtained from the Besançon model of population synthesis and analysis of optical and near-infrared star counts. The Galactic potential is computed self-consistently, in agreement with Hipparcos results and the observed rotation curve. Constraints are posed on the outer bulge structure, the warped and flared disc, the thick disc and the spheroid populations. The model is tuned to produce reliable predictions in the visible and the near-infrared in wide photometric bands from U to K. Finally, we describe applications such as photometric and astrometric simulations and a new classification tool based on a Bayesian probability estimator, which could be used in the framework of Virtual Observatories. As examples, samples of simulated star counts at different wavelengths and directions are also given.

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SDSS-III: MASSIVE SPECTROSCOPIC SURVEYS OF THE DISTANT UNIVERSE, THE MILKY WAY, AND EXTRA-SOLAR PLANETARY SYSTEMS

2011-08-09

Daniel J. Eisenstein , David H. Weinberg , Eric Agol +7 more

Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, … Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Lyα forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z ≈ 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = λ/Δλ ≈ 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R ≈ 30,000), high signal-to-noise ratio (S/N ⩾ 100 per resolution element), H-band (1.51 μm < λ < 1.70 μm) spectra of 105 evolved, late-type stars, measuring separate abundances for ∼15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10–40 m s−1, ∼24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z ⩾ 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS.

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Updated Opal Opacities

1996-06-01

Carlos A. Iglesias , F. J. Rogers

view Abstract Citations (2552) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Updated Opal Opacities Iglesias, Carlos A. ; Rogers, Forrest J. Abstract The reexamination of … view Abstract Citations (2552) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Updated Opal Opacities Iglesias, Carlos A. ; Rogers, Forrest J. Abstract The reexamination of astrophysical opacities has eliminated gross discrepancies between a variety of observations and theoretical calculations; thus allowing for more detailed tests of stellar models. A number of such studies indicate that model results are sensitive to modest changes in the opacity. Consequently, it is desirable to update available opacity databases with recent improvements in physics, refinements of element abundance, and other such factors affecting the results. Updated OPAL Rosseland mean opacities are presented. The new results have incorporated improvements in the physics and numerical procedures as well as corrections. The main opacity changes are increases of as much as 20% for Population I stars due to the explicit inclusion of 19 metals (compared to 12 metals in the earlier calculations) with the other modifications introducing opacity changes smaller than 10%. In addition, the temperature and density range covered by the updated opacity tables has been extended. As before, the tables allow accurate interpolation in density and temperature as well as hydrogen, helium, carbon, oxygen, and metal mass fractions. Although a specific metal composition is emphasized, opacity tables for different metal distributions can be made readily available. The updated opacities are compared to other work. Publication: The Astrophysical Journal Pub Date: June 1996 DOI: 10.1086/177381 Bibcode: 1996ApJ...464..943I Keywords: ATOMIC DATA; ATOMIC PROCESSES; STARS: INTERIORS full text sources ADS |

The Evolution of Viscous Discs and the Origin of the Nebular Variables

1974-09-01

D. Lynden–Bell , J. E. Pringle

The evolution of discs under the action of viscosity is studied by both similarity solutions and Green's functions. The angular momentum is steadily concentrated onto a small fraction of the … The evolution of discs under the action of viscosity is studied by both similarity solutions and Green's functions. The angular momentum is steadily concentrated onto a small fraction of the mass which orbits at greater and greater radii while the rest is accreted onto the central body. We assume that the angular momentum excess of a proto-star is initially concentrated onto one-third of the total mass which forms a disc orbiting the new-born star. Viscous dissipation in this disc will cause it to shine with a luminosity greater than the final main sequence star for a period of 105 yr or so. Most of the properties of T Tauri stars can be explained as a consequence of disc evolution. Flares in Flare stars are interpreted as the entry of blobs of an old disc into the late type stellar atmospheres. On this hypothesis flaring activity could be observed in M stars of up to 5 × 108 yr old, and planetary systems will be common. Disc solutions appropriate to dwarf novae and X-ray sources are also given.

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Unified Models for Active Galactic Nuclei and Quasars

1993-09-01

Robert Antonucci

My life has been an interesting voyage. I became an astronomer because I could not imagine living on Earth and not trying to understand how the Universe works. My scientific … My life has been an interesting voyage. I became an astronomer because I could not imagine living on Earth and not trying to understand how the Universe works. My scientific career has revolved around observing the motions of stars within galaxies and the ...Read More

On the variation of the initial mass function

2001-04-01

Pavel Kroupa

A universal initial mass function (IMF) is not intuitive, but so far no convincing evidence for a variable IMF exists. The detection of systematic variations of the IMF with star-forming … A universal initial mass function (IMF) is not intuitive, but so far no convincing evidence for a variable IMF exists. The detection of systematic variations of the IMF with star-forming conditions would be the Rosetta Stone for star formation. In this contribution an average or Galactic-field IMF is defined, stressing that there is evidence for a change in the power-law index at only two masses: near 0.5 M⊙ and near 0.08 M⊙. Using this supposed universal IMF, the uncertainty inherent in any observational estimate of the IMF is investigated by studying the scatter introduced by Poisson noise and the dynamical evolution of star clusters. It is found that this apparent scatter reproduces quite well the observed scatter in power-law index determinations, thus defining the fundamental limit within which any true variation becomes undetectable. The absence of evidence for a variable IMF means that any true variation of the IMF in well-studied populations must be smaller than this scatter. Determinations of the power-law indices α are subject to systematic errors arising mostly from unresolved binaries. The systematic bias is quantified here, with the result that the single-star IMFs for young star clusters are systematically steeper by Δα≈0.5 between 0.1 and 1 M⊙ than the Galactic-field IMF, which is populated by, on average, about 5-Gyr-old stars. The MFs in globular clusters appear to be, on average, systematically flatter than the Galactic-field IMF (Piotto & Zoccali; Paresce & De Marchi), and the recent detection of ancient white-dwarf candidates in the Galactic halo and the absence of associated low-mass stars (Ibata et al.; Méndez & Minniti) suggest a radically different IMF for this ancient population. Star formation in higher metallicity environments thus appears to produce relatively more low-mass stars. While still tentative, this is an interesting trend, being consistent with a systematic variation of the IMF as expected from theoretical arguments.

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DWARF GALAXIES OF THE LOCAL GROUP

1998-09-01

Mario Mateo

▪ Abstract The Local Group dwarf galaxies offer a unique window to the detailed properties of the most common type of galaxy in the Universe. In this review, I update … ▪ Abstract The Local Group dwarf galaxies offer a unique window to the detailed properties of the most common type of galaxy in the Universe. In this review, I update the census of Local Group dwarfs based on the most recent distance and radial velocity determinations. I then discuss the detailed properties of this sample, including (a) the integrated photometric parameters and optical structures of these galaxies, (b) the content, nature, and distribution of their interstellar medium (ISM), (c) their heavy-element abundances derived from both stars and nebulae, (d) the complex and varied star-formation histories of these dwarfs, (e) their internal kinematics, stressing the relevance of these galaxies to the “dark matter problem” and to alternative interpretations, and (f) evidence for past, ongoing, and future interactions of these dwarfs with other galaxies in the Local Group and beyond. To complement the discussion and to serve as a foundation for future work, I present an extensive set of basic observational data in tables that summarize much of what we know and do not know about these nearby dwarfs. Our understanding of these galaxies has grown impressively in the past decade, but fundamental puzzles remain that will keep the Local Group at the forefront of galaxy evolution studies for some time.

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Validation of the new Hipparcos reduction

2007-08-13

F. van Leeuwen

Context.A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than magnitude Hp = 8 to be … Context.A new reduction of the astrometric data as produced by the Hipparcos mission has been published, claiming accuracies for nearly all stars brighter than magnitude Hp = 8 to be better, by up to a factor 4, than in the original catalogue. Aims.The new Hipparcos astrometric catalogue is checked for the quality of the data and the consistency of the formal errors as well as the possible presence of error correlations. The differences with the earlier publication are explained. Methods. The internal errors are followed through the reduction process, and the external errors are investigated on the basis of a comparison with radio observations of a small selection of stars, and the distribution of negative parallaxes. Error correlation levels are investigated and the reduction by more than a factor 10 as obtained in the new catalogue is explained. Results.The formal errors on the parallaxes for the new catalogue are confirmed. The presence of a small amount of additional noise, though unlikely, cannot be ruled out. Conclusions. The new reduction of the Hipparcos astrometric data provides an improvement by a factor 2.2 in the total weight compared to the catalogue published in 1997, and provides much improved data for a wide range of studies on stellar luminosities and local galactic kinematics.

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Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 $M_{\odot}$, and from $Z=0.0004$ to 0.03

2000-02-01

L. Girardi , A. Bressan , G. Bertelli +1 more

We present a large grid of stellar evolutionary tracks, which are suitable to modelling star clusters and galaxies by means of population synthesis. The tracks are presented for the initial … We present a large grid of stellar evolutionary tracks, which are suitable to modelling star clusters and galaxies by means of population synthesis. The tracks are presented for the initial chemical compositions , , , , (solar composition), and . They are computed with updated opacities and equation of state, and a moderate amount of convective overshoot. The range of initial masses goes from to , and the evolutionary phases extend from the zero age main sequence (ZAMS) till either the thermally pulsing AGB regime or carbon ignition. We also present an additional set of models with solar composition, computed using the classical Schwarzschild criterion for convective boundaries. From all these tracks, we derive the theoretical isochrones in the Johnson-Cousins UBVRIJHK broad-band photometric system.

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<scp>parsec</scp>: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code

2012-10-29

A. Bressan , Paola Marigo , L. Girardi +4 more

We present the updated version of the code used to compute stellar evolutionary tracks in Padova. It is the result of a thorough revision of the major input physics, together … We present the updated version of the code used to compute stellar evolutionary tracks in Padova. It is the result of a thorough revision of the major input physics, together with the inclusion of the pre-main sequence phase, not present in our previous releases of stellar models. Another innovative aspect is the possibility of promptly generating accurate opacity tables fully consistent with any selected initial chemical composition, by coupling the Opacity Project At Livermore (OPAL) data at high temperatures to the molecular opacities computed with our æsopus code. In this work, we present extended sets of stellar evolutionary models for various initial chemical compositions, while other sets with different metallicities and/or different distributions of heavy elements are being computed. For the present release of models, we adopt the solar distribution of heavy elements from the recent revision by Caffau et al., corresponding to a Sun's metallicity Z ≃ 0.0152. From all computed sets of stellar tracks, we also derive isochrones in several photometric systems. The aim is to provide the community with the basic tools to model star clusters and galaxies by means of population synthesis techniques.

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The Two Micron All Sky Survey (2MASS)

2006-01-24

Michael F. Skrutskie , R. M. Cutri , R. Stiening +7 more

Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imaging data covering 99.998% of the celestial sphere in the near-infrared J … Between 1997 June and 2001 February the Two Micron All Sky Survey (2MASS) collected 25.4 Tbytes of raw imaging data covering 99.998% of the celestial sphere in the near-infrared J (1.25 μm), H (1.65 μm), and Ks (2.16 μm) bandpasses. Observations were conducted from two dedicated 1.3 m diameter telescopes located at Mount Hopkins, Arizona, and Cerro Tololo, Chile. The 7.8 s of integration time accumulated for each point on the sky and strict quality control yielded a 10 σ point-source detection level of better than 15.8, 15.1, and 14.3 mag at the J, H, and Ks bands, respectively, for virtually the entire sky. Bright source extractions have 1 σ photometric uncertainty of <0.03 mag and astrometric accuracy of order 100 mas. Calibration offsets between any two points in the sky are <0.02 mag. The 2MASS All-Sky Data Release includes 4.1 million compressed FITS images covering the entire sky, 471 million source extractions in a Point Source Catalog, and 1.6 million objects identified as extended in an Extended Source Catalog.

The Infrared Array Camera (IRAC) for the Spitzer Space Telescope

2004-09-01

G. G. Fazio , Joseph L. Hora , Lori Allen +7 more

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, … The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 microns. Two nearly adjacent 5.2x5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256x256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.

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GaiaData Release 1

2016-09-15

A. G. A. Brown , A. Vallenari , T. Prusti +7 more

At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than … At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. We summarize Gaia DR1 and provide illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Gaia DR1 consists of: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set,consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ~3000 Cepheid and RR Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas/yr for the proper motions. A systematic component of ~0.3 mas should be added to the parallax uncertainties. For the subset of ~94000 Hipparcos stars in the primary data set, the proper motions are much more precise at about 0.06 mas/yr. For the secondary astrometric data set, the typical uncertainty of the positions is ~10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ~0.03 mag over the magnitude range 5 to 20.7. Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.

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Gaia Data Release 2

2018-04-24

A. G. A. Brown , A. Vallenari , T. Prusti +7 more

Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In … Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G BP (330–680 nm) and G RP (630–1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia -CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

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MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA)

2010-12-15

Bill Paxton , Lars Bildsten , Aaron Dotter +3 more

Stellar physics and evolution calculations enable a broad range of research in astrophysics. Modules for Experiments in Stellar Astrophysics (MESA) is a suite of open source, robust, efficient, thread-safe libraries … Stellar physics and evolution calculations enable a broad range of research in astrophysics. Modules for Experiments in Stellar Astrophysics (MESA) is a suite of open source, robust, efficient, thread-safe libraries for a wide range of applications in computational stellar astrophysics. A one-dimensional stellar evolution module, MESAstar, combines many of the numerical and physics modules for simulations of a wide range of stellar evolution scenarios ranging from very low mass to massive stars, including advanced evolutionary phases. MESAstar solves the fully coupled structure and composition equations simultaneously. It uses adaptive mesh refinement and sophisticated timestep controls, and supports shared memory parallelism based on OpenMP. State-of-the-art modules provide equation of state, opacity, nuclear reaction rates, element diffusion data, and atmosphere boundary conditions. Each module is constructed as a separate Fortran 95 library with its own explicitly defined public interface to facilitate independent development. Several detailed examples indicate the extensive verification and testing that is continuously performed and demonstrate the wide range of capabilities that MESA possesses. These examples include evolutionary tracks of very low mass stars, brown dwarfs, and gas giant planets to very old ages; the complete evolutionary track of a 1 M☉ star from the pre-main sequence (PMS) to a cooling white dwarf; the solar sound speed profile; the evolution of intermediate-mass stars through the He-core burning phase and thermal pulses on the He-shell burning asymptotic giant branch phase; the interior structure of slowly pulsating B Stars and Beta Cepheids; the complete evolutionary tracks of massive stars from the PMS to the onset of core collapse; mass transfer from stars undergoing Roche lobe overflow; and the evolution of helium accretion onto a neutron star. MESA can be downloaded from the project Web site (http://mesa.sourceforge.net/).

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The Photodetector Array Camera and Spectrometer (PACS) on the HerschelSpace Observatory

2010-07-01

A. Poglitsch , C. Waelkens , N. Geis +7 more

The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) … The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments on ESA's far infrared and submillimetre observatory. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16x25 pixels, each, and two filled silicon bolometer arrays with 16x32 and 32x64 pixels, respectively, to perform integral-field spectroscopy and imaging photometry in the 60-210μ m wavelength regime. In photometry mode, it simultaneously images two bands, 60-85μ m or 85-125μ\m and 125-210μ m, over a field of view of ~1.75'x3.5', with close to Nyquist beam sampling in each band. In spectroscopy mode, it images a field of 47"x47", resolved into 5x5 pixels, with an instantaneous spectral coverage of ~1500km/s and a spectral resolution of ~175km/s. We summarise the design of the instrument, describe observing modes, calibration, and data analysis methods, and present our current assessment of the in-orbit performance of the instrument based on the Performance Verification tests. PACS is fully operational, and the achieved performance is close to or better than the pre-launch predictions.

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Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics beyond ΛCDM

2019-05-01

Adam G. Riess , Stefano Casertano , Wenlong Yuan +2 more

Abstract We present an improved determination of the Hubble constant from Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud (LMC). These were obtained with … Abstract We present an improved determination of the Hubble constant from Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud (LMC). These were obtained with the same WFC3 photometric system used to measure extragalactic Cepheids in the hosts of SNe Ia. Gyroscopic control of HST was employed to reduce overheads while collecting a large sample of widely separated Cepheids. The Cepheid period–luminosity relation provides a zero-point-independent link with 0.4% precision between the new 1.2% geometric distance to the LMC from detached eclipsing binaries (DEBs) measured by Pietrzyński et al. and the luminosity of SNe Ia. Measurements and analysis of the LMC Cepheids were completed prior to knowledge of the new DEB LMC distance. Combined with a refined calibration of the count-rate linearity of WFC3-IR with 0.1% precision, these three improved elements together reduce the overall uncertainty in the geometric calibration of the Cepheid distance ladder based on the LMC from 2.5% to 1.3%. Using only the LMC DEBs to calibrate the ladder, we find H 0 = 74.22 ± 1.82 km s −1 Mpc −1 including systematic uncertainties, 3% higher than before for this particular anchor. Combining the LMC DEBs, masers in NGC 4258, and Milky Way parallaxes yields our best estimate: H 0 = 74.03 ± 1.42 km s −1 Mpc −1 , including systematics, an uncertainty of 1.91%–15% lower than our best previous result. Removing any one of these anchors changes H 0 by less than 0.7%. The difference between H 0 measured locally and the value inferred from Planck CMB and ΛCDM is 6.6 ± 1.5 km s −1 Mpc −1 or 4.4 σ ( P = 99.999% for Gaussian errors) in significance, raising the discrepancy beyond a plausible level of chance. We summarize independent tests showing that this discrepancy is not attributable to an error in any one source or measurement, increasing the odds that it results from a cosmological feature beyond ΛCDM.

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Starburst99: Synthesis Models for Galaxies with Active Star Formation

1999-07-01

Claus Leitherer , D. Schaerer , Jeffrey D. Goldader +6 more

Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data … Starburst99 is a comprehensive set of model predictions for spectrophotometric and related properties of galaxies with active star formation. The models are an improved and extended version of the data set previously published by Leitherer & Heckman. We have upgraded our code by implementing the latest set of stellar evolution models of the Geneva group and the model atmosphere grid compiled by Lejeune et al. Several predictions which were not included in the previous publication are shown here for the first time. The models are presented in a homogeneous way for five metallicities between Z = 0.040 and 0.001 and three choices of the initial mass function. The age coverage is 106—109 yr. We also show the spectral energy distributions which are used to compute colors and other quantities. The full data set is available for retrieval at a Web site, which allows users to run specific models with nonstandard parameters as well. We also make the source code available to the community.

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Binary Companions of Evolved Stars in APOGEE DR14: Search Method and Catalog of ∼5000 Companions

2018-06-18

Adrian M. Price-Whelan , David W. Hogg , Hans‐Walter Rix +7 more

Abstract Multi-epoch radial velocity measurements of stars can be used to identify stellar, substellar, and planetary-mass companions. Even a small number of observation epochs can be informative about companions, though … Abstract Multi-epoch radial velocity measurements of stars can be used to identify stellar, substellar, and planetary-mass companions. Even a small number of observation epochs can be informative about companions, though there can be multiple qualitatively different orbital solutions that fit the data. We have custom-built a Monte Carlo sampler ( The Joker ) that delivers reliable (and often highly multimodal) posterior samplings for companion orbital parameters given sparse radial velocity data. Here we use The Joker to perform a search for companions to 96,231 red giant stars observed in the APOGEE survey (DR14) with ≥3 spectroscopic epochs. We select stars with probable companions by making a cut on our posterior belief about the amplitude of the variation in stellar radial velocity induced by the orbit. We provide (1) a catalog of 320 companions for which the stellar companion’s properties can be confidently determined, (2) a catalog of 4898 stars that likely have companions, but would require more observations to uniquely determine the orbital properties, and (3) posterior samplings for the full orbital parameters for all stars in the parent sample. We show the characteristics of systems with confidently determined companion properties and highlight interesting systems with candidate compact object companions.

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GaiaEarly Data Release 3

2020-12-03

A. G. A. Brown , A. Vallenari , T. Prusti +7 more

We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list … We present the early installment of the third Gaia data release, Gaia EDR3, consisting of astrometry and photometry for 1.8 billion sources brighter than magnitude 21, complemented with the list of radial velocities from Gaia DR2. Gaia EDR3 contains celestial positions and the apparent brightness in G for approximately 1.8 billion sources. For 1.5 billion of those sources, parallaxes, proper motions, and the (G_BP-G_RP) colour are also available. The passbands for G, G_BP, and G_RP are provided as part of the release. For ease of use, the 7 million radial velocities from Gaia DR2 are included in this release, after the removal of a small number of spurious values. New radial velocities will appear as part of Gaia DR3. Finally, Gaia EDR3 represents an updated materialisation of the celestial reference frame (CRF) in the optical, the Gaia-CRF3, which is based solely on extragalactic sources. The creation of the source list for Gaia EDR3 includes enhancements that make it more robust with respect to high proper motion stars, and the disturbing effects of spurious and partially resolved sources. The source list is largely the same as that for Gaia DR2, but it does feature new sources and there are some notable changes. The source list will not change for Gaia DR3. Gaia EDR3 represents a significant advance over Gaia DR2, with parallax precisions increased by 30 percent, proper motion precisions increased by a factor of 2, and the systematic errors in the astrometry suppressed by 30--40 percent for the parallaxes and by a factor ~2.5 for the proper motions. The photometry also features increased precision, but above all much better homogeneity across colour, magnitude, and celestial position. A single passband for G, G_BP, and G_RP is valid over the entire magnitude and colour range, with no systematics above the 1 percent level.

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Active Galactic Nuclei

1989-01-01

V. Beckmann , C. R. Shrader

GaiaData Release 3

2022-06-10

A. Vallenari , A. G. A. Brown , T. Prusti +7 more

We present the third data release of the European Space Agency's Gaia mission, GDR3. The GDR3 catalogue is the outcome of the processing of raw data collected with the Gaia … We present the third data release of the European Space Agency's Gaia mission, GDR3. The GDR3 catalogue is the outcome of the processing of raw data collected with the Gaia instruments during the first 34 months of the mission by the Gaia Data Processing and Analysis Consortium. The GDR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the G, G$_{BP}$, and G$_{RP}$ pass-bands already present in the Early Third Data Release. GDR3 introduces an impressive wealth of new data products. More than 33 million objects in the ranges $G_{rvs} < 14$ and $3100 <T_{eff} <14500 $, have new determinations of their mean radial velocities based on data collected by Gaia. We provide G$_{rvs}$ magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. Mean Gaia spectra are made available to the community. The GDR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BPRP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types. GDR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some $800\,000$ astrometric, spectroscopic and eclipsing binaries. More than $150\,000$ Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BPRP spectral data are published for about 60\,000 asteroids. Finally, an additional data set is provided, namely the Gaia Andromeda Photometric Survey (abridged)

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Gaia Data Release 2

2018-04-24

L. Lindegren , Jesús Hernández , A. Bombrun +7 more

Gaia Data Release 2 (Gaia DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency Gaia satellite … Gaia Data Release 2 (Gaia DR2) contains results for 1693 million sources in the magnitude range 3 to 21 based on observations collected by the European Space Agency Gaia satellite during the first 22 months of its operational phase. We describe the input data, models, and processing used for the astrometric content of Gaia DR2, and the validation of these results performed within the astrometry task. Some 320 billion centroid positions from the pre-processed astrometric CCD observations were used to estimate the five astrometric parameters (positions, parallaxes, and proper motions) for 1332 million sources, and approximate positions at the reference epoch J2015.5 for an additional 361 million mostly faint sources. Special validation solutions were used to characterise the random and systematic errors in parallax and proper motion. For the sources with five-parameter astrometric solutions, the median uncertainty in parallax and position at the reference epoch J2015.5 is about 0.04 mas for bright (G<14 mag) sources, 0.1 mas at G=17 mag, and 0.7 mas at G=20 mag. In the proper motion components the corresponding uncertainties are 0.05, 0.2, and 1.2 mas/yr, respectively. The optical reference frame defined by Gaia DR2 is aligned with ICRS and is non-rotating with respect to the quasars to within 0.15 mas/yr. From the quasars and validation solutions we estimate that systematics in the parallaxes depending on position, magnitude, and colour are generally below 0.1 mas, but the parallaxes are on the whole too small by about 0.03 mas. Significant spatial correlations of up to 0.04 mas in parallax and 0.07 mas/yr in proper motion are seen on small (<1 deg) and intermediate (20 deg) angular scales. Important statistics and information for the users of the Gaia DR2 astrometry are given in the appendices.

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A grid of MARCS model atmospheres for late-type stars

2008-05-29

B. Gustafsson , B. Edvardsson , Kimmo Eriksson +3 more

Context. In analyses of stellar spectra and colours, and for the analysis of integrated light from galaxies, a homogeneous grid of model atmospheres of late-type stars and corresponding flux spectra … Context. In analyses of stellar spectra and colours, and for the analysis of integrated light from galaxies, a homogeneous grid of model atmospheres of late-type stars and corresponding flux spectra is needed.

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Search for higher harmonic signals from close white dwarf binaries in the mHz band

2025-06-25

NULL AUTHOR_ID | Physical Review Letters

Giant Outer Transiting Exoplanet Mass (GOT ‘EM) Survey. VI. Confirmation of a Long-period Giant Planet Discovered with a Single TESS Transit

2025-06-25

Zahra Essack , Diana Dragomir , Paul A. Dalba +7 more | The Astronomical Journal

Abstract We report the discovery and confirmation of TOI-4465 b, a 1.25 R J <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> <mml:msub> <mml:mi>R</mml:mi> <mml:mi mathvariant="normal">J</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> … Abstract We report the discovery and confirmation of TOI-4465 b, a 1.25 R J <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> <mml:msub> <mml:mi>R</mml:mi> <mml:mi mathvariant="normal">J</mml:mi> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.08</mml:mn> <mml:msub> <mml:mi>R</mml:mi> <mml:mi mathvariant="normal">J</mml:mi> </mml:msub> </mml:mrow> </mml:msubsup> </mml:math> , 5.89 M J ± 0.26 M J giant planet orbiting a G dwarf star at d ≃ 122 pc. The planet was detected as a single-transit event in data from Sector 40 of the Transiting Exoplanet Survey Satellite (TESS) mission. Radial velocity (RV) observations of TOI-4465 showed a planetary signal with an orbital period of ∼102 days and an orbital eccentricity of e = 0.24 ± 0.01. TESS reobserved TOI-4465 in Sector 53 and Sector 80 but did not detect another transit of TOI-4465 b, as the planet was not expected to transit during these observations based on the RV period. A global ground-based photometry campaign was initiated to observe another transit of TOI-4465 b after the RV period determination. The ∼12 hr long transit event was captured from multiple sites around the world and included observations from 24 citizen scientists, confirming the orbital period as ∼102 days. TOI-4465 b is a relatively dense (3.73 ± 0.53 g cm −3 ), temperate (375–478 K) giant planet. Based on giant planet structure models, TOI-4465 b appears to be enriched in heavy elements at a level consistent with late-stage accretion of icy planetesimals. Additionally, we explore TOI-4465 b’s potential for atmospheric characterization and obliquity measurement. Increasing the number of long-period planets by confirming single-transit events is crucial for understanding the frequency and demographics of planet populations in the outer regions of planetary systems.

Three-dimensional Orbital Architectures and Detectability of Adjacent Companions to Hot Jupiters

2025-06-25

Thomas MacLean , Juliette Becker | The Astrophysical Journal

Abstract The orbital properties of the (as yet) small population of hot Jupiters with nearby planetary companions provide valuable constraints on the past migration processes of these systems. In this … Abstract The orbital properties of the (as yet) small population of hot Jupiters with nearby planetary companions provide valuable constraints on the past migration processes of these systems. In this work, we explore the likelihood that dynamical perturbations could cause nearby inner or outer companions to a hot Jupiter to leave the transiting plane, potentially leaving these companions undetected despite their presence at formation. Using a combination of analytical and numerical models, we examine the effects of stellar evolution on hot Jupiter systems with nearby companions and identify several possible outcomes. We find that while inner companions are generally unlikely to leave the transiting plane, outer companions are more prone to decoupling from the hot Jupiter and becoming nontransiting, depending on the system’s initial orbital architecture. Additionally, we observe a range of dynamical behaviors, including overall stability, inclination excitation, and, in some cases, instability leading to the ejection or collision of planets. We also show that the effect of stellar obliquity (with respect to the mean planet of the planets) is to amplify these effects and potentially cause outer companions to attain nonmutually transiting configurations more often. Our results highlight the complex dynamical pathways shaping the architectures of hot Jupiter systems.

GULP. II. Hierarchical Distribution and Evolution of Young Stellar Structures in NGC 4449

2025-06-25

Beena Meena , Elena Sabbi , Peter Zeidler +7 more | The Astrophysical Journal

Abstract We investigate the hierarchical distribution and evolution of young stellar structures in the dwarf starburst galaxy NGC 4449 using data from the GULP survey. By analyzing the spatial distribution … Abstract We investigate the hierarchical distribution and evolution of young stellar structures in the dwarf starburst galaxy NGC 4449 using data from the GULP survey. By analyzing the spatial distribution of field stars younger than 100 Myr, we identify large-scale stellar complexes and substructures using HDBSCAN—a density-based clustering algorithm—and trace their evolution over time. While comparing these stellar structures in different regions of the galaxy, we find that the central bar-like region shows a clear expansion of the structures within the first ∼60 Myr, while the arm-like structure in the northeast shows no discernible trend, possibly due to external perturbations from tidal interactions with a neighboring galaxy. An age-dependent two-point correlation function (TPCF) analysis shows that young stars exhibit a strong hierarchical distribution, with clustering strength decreasing over time. The power-law slope of the TPCF, which starts at α ∼ 0.65 for stars younger than 5 Myr, shows a slight decline to α ∼ 0.4 for stars older than 50 Myr, though it does not reach a completely flat (random) distribution. This trend indicates a subtle weakening of structural hierarchy among young (<100 Myr) stars, which is primarily driven by internal stellar motions. Future work will extend this analysis to the remaining 26 galaxies in the GULP survey to better constrain the role of the galactic environment in shaping the hierarchical evolution of young stellar populations.

Continuous Habitable Zone Metric for Prioritizing Habitable Worlds Observatory Targets

2025-06-25

Austin Ware , Patrick Young | The Astrophysical Journal

Abstract Future direct imaging space telescopes, such as NASA’s Habitable Worlds Observatory (HWO), will be the first capable of both detecting and characterizing terrestrial exoplanets in the habitable zones (HZs) … Abstract Future direct imaging space telescopes, such as NASA’s Habitable Worlds Observatory (HWO), will be the first capable of both detecting and characterizing terrestrial exoplanets in the habitable zones (HZs) of nearby Sun-like stars. Since this will require a significant amount of time and resources for even a single system or exoplanet, the likelihood that a system will host detectable life should be considered when prioritizing observations. One method of prioritization is to estimate the likelihood that an exoplanet has remained continuously within the HZ long enough for life to emerge and make a detectable impact on the atmosphere. We utilize a Bayesian method to calculate the likelihood that a given orbital radius around a star is currently in the 2 Gyr continuous habitable zone (CHZ 2 ), the approximate time it took life on Earth to significantly oxygenate the atmosphere. We apply this method to the 164 stars in the NASA Exoplanet Exploration Program Mission Star List for HWO, representing a preliminary sample of Sun-like stars with HZs most accessible to a future direct imaging mission. By considering the CHZ 2 likelihood at all orbital radii outside a hypothetical inner working angle for HWO, we define a metric for prioritizing targets according to the accessibility and total extent of the CHZ 2 . We find that the CHZ 2 metric peaks between 3 and 4 Gyr for late F and early G dwarfs, but tentatively determine that stars earlier than ∼F3 or hotter than ∼6600 K are unlikely to have a CHZ 2 at the time of observation.

Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths

2025-06-24

Brandon Park Coy , Jegug Ih , Edwin S. Kite +7 more | The Astrophysical Journal

Abstract Determining which rocky exoplanets have atmospheres, and why, is a key goal for the James Webb Space Telescope. So far, emission observations of individual rocky exoplanets orbiting M stars … Abstract Determining which rocky exoplanets have atmospheres, and why, is a key goal for the James Webb Space Telescope. So far, emission observations of individual rocky exoplanets orbiting M stars (M-Earths) have not provided definitive evidence for atmospheres. Here, we synthesize emission data for M-Earths and find a trend in measured brightness temperatures (ratioed to its theoretical maximum value) as a function of instellation. However, the statistical evidence of this trend is dependent on the choice of stellar model, and we consider its identification tentative. We show that this trend can be explained by either the onset of thin/tenuous (<1 bar) CO 2 -rich atmospheres on colder worlds, or a population of bare rocks with stronger space weathering and/or coarser regolith on closer-in worlds. Such grain coarsening may be caused by sintering near the melting point of rock or frequent volcanic resurfacing. Furthermore, we highlight considerations when testing rocky planet hypotheses at the population level, including the choice of instrument, stellar modeling, and how brightness temperatures are derived. We also find that fresh (unweathered) fine-grained surfaces can serve as a false positive to the detection of moderate atmospheric heat redistribution through eclipse observations. However, we argue that such surfaces are unlikely given the ubiquity of space weathering in the solar system, the low albedo of solar system airless bodies, and the high stellar wind environments of M-Earths. Emission data from a larger sample of M-Earths will be able to confirm or reject this tentative trend and diagnose its cause through spectral characterization.

A Candidate Giant Planet Companion to the Massive, Young White Dwarf GALEX J071816.4+373139 Informs the Occurrence of Giant Planets Orbiting B Stars

2025-06-24

Sihao Cheng , Kevin C. Schlaufman , Ilaria Caiazzo | The Astronomical Journal

Abstract It has been suggested that giant planet occurrence peaks for stars with M * ≈ 3 M ⊙ at a value a factor of 4 higher than observed for … Abstract It has been suggested that giant planet occurrence peaks for stars with M * ≈ 3 M ⊙ at a value a factor of 4 higher than observed for solar-mass stars. This population of giant planets predicted to frequently orbit main-sequence B stars at a ≈ 10 au is difficult to characterize during the few hundred million years while fusion persists in their host stars. By the time those stars become massive, young white dwarfs, any giant planets present would still be luminous as a consequence of their recent formation. From an initial sample of 2195 Gaia-identified massive, young white dwarfs, we use homogeneous Spitzer Infrared Array Camera (IRAC) photometry to search for evidence of unresolved giant planets. For 30 systems, these IRAC data provide sensitivity to objects with M ≲ 10 M Jup , and we identify one candidate with M ≈ 4 M Jup orbiting the white dwarf GALEX J071816.4+373139. Correcting for the possibility that some of the white dwarfs in our sample result from mergers, we find a giant planet occurrence <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>η</mml:mi> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>GP</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> for stars with initial masses M * ≳ 3 M ⊙ . Our occurrence inference is consistent with both the Doppler-inferred occurrence of giant planets orbiting M * ≈ 2 M ⊙ giant stars and the theoretically predicted factor of 4 enhancement in the occurrence of giant planets orbiting M * ≈ 3 M ⊙ stars relative to solar-mass stars. Future James Webb Space Telescope NIRCam observations of our sample would provide sensitivity to Saturn-mass planets and thereby a definitive estimate of the occurrence of giant planets orbiting stars with M * ≳ 3 M ⊙ .

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Post-common envelope evolution of helium-core white dwarfs

2025-06-23

L. G. Althaus , Leila M. Calcaferro , A. H. Córsico +1 more | Astronomy and Astrophysics

Helium-core white dwarfs (He WDs) from the common envelope (CE) channel offer insights into binary evolution and compact remnant formation. Their cooling rates influence their detectability and affect age estimates … Helium-core white dwarfs (He WDs) from the common envelope (CE) channel offer insights into binary evolution and compact remnant formation. Their cooling rates influence their detectability and affect age estimates of close binaries. Compared with those from stable Roche-lobe overflow (SRLOF), CE He WDs experience a distinct mass-loss history, leading to fundamental differences in the post-CE evolution of the resulting WDs. We investigate how the H-envelope mass (M_ H) affects the cooling evolution of CE He WDs. In particular, we analyze how the bifurcation point, which separates the degenerate He core from the envelope, determines the remaining M_ H and the presence of residual H burning. We computed evolutionary sequences for He WDs of $0.20 ⊙ $ to $0.42 ⊙ $, from a $1 ⊙ $ progenitor on the red giant branch. Using the La Plata stellar evolution code (LPCODE), we followed their evolution from the post-CE phase to the cooling track, identifying two pathways depending on the remaining H: (i) non-flashing sequences, in which WDs cool without prior nuclear burning, and (ii) flashing sequences, in which H shell flashes reshape the envelope before cooling. CE He WDs with minimal M_ H cool rapidly after formation, with negligible residual H burning. For a sample with T_ eff between $12,000$ and $27,000$ K, our models predict ages of $5–130$ Myr, increasing to slightly above $300$ Myr for eff < 10,000 K, which is much younger than those from SRLOF sequences. In contrast, WDs with more M_ H sustain residual nuclear burning, delaying cooling. At eff < 10,000 K, these models predict ages of several Gyr, far exceeding those from SRLOF and minimal-envelope sequences. Flashing sequences significantly extend the pre-WD phase compared to non-flashing sequences, but this phase remains much shorter than in SRLOF evolution. The amount of $M_ H $ also affects mass and surface gravity estimates, introducing systematic differences from SRLOF WDs at a given T_ eff. The evolutionary paths of CE He WDs differ significantly from those of SRLOF-produced WDs. Minimal-envelope CE WDs cool rapidly and merge at lower temperatures, while those with sustained H burning remain bright for longer and merge at higher temperatures. These differences with SRLOF WDs are critical for understanding the evolutionary history and final fate of He WDs in compact binaries.

The Disks In Scorpius–Centaurus Survey (DISCS). I. Four Newly Resolved Debris Disks in Polarized Intensity Light

2025-06-23

Justin Hom , Thomas M. Esposito , Katie A. Crotts +7 more | The Astronomical Journal

Abstract The presence of infrared excesses around stars directly correlates with spatially resolved imaging detections of circumstellar disks at both millimeter and optical/near-infrared wavelengths. High-contrast imagers have resolved dozens of … Abstract The presence of infrared excesses around stars directly correlates with spatially resolved imaging detections of circumstellar disks at both millimeter and optical/near-infrared wavelengths. High-contrast imagers have resolved dozens of circumstellar disks with scattered light polarimetric imaging. Many of these detections are members of the Scorpius–Centaurus OB association, demonstrating it to be a rich sample for investigating planetary system architectures and planet–disk interactions. With the goal of expanding the sample of directly imaged debris disks in Scorpius–Centaurus, we conducted the Disks In Scorpius–Centaurus Survey, leveraging knowledge of high-IR excesses and the power of high-contrast polarimetric differential imaging. In combination with the GPIES polarimetric disk survey, we observe seven new Scorpius–Centaurus targets to achieve a 60% complete survey of debris disks with IR excesses exceeding 2.5 × 10 −4 , resolving four new debris disks. HD 98363, HD 109832, and HD 146181 are resolved for the first time, and HD 112810 is resolved for the first time in polarized intensity. We identify morphological structures that may be indications of planet–disk interactions. We place the systems in the greater context of resolved debris disks, identifying order of magnitude differences in scattered light contrast for a given IR excess, implying gaps in our understanding of the smallest and largest dust grains of a system. We conclude that while thermal emission measurements are correlated with scattered light detection, they poorly predict the magnitude of scattered light brightness. We also establish Scorpius–Centaurus debris disks as critical benchmarks in understanding the properties of disks in the scattering regime.

Main-oval Auroral Emission from a T6 Brown Dwarf: Observations, Modeling, and Astrometry

2025-06-23

J. C. Guirado , J. B. Climent , J. D. Bergasa +3 more | The Astrophysical Journal

Abstract From a series of 5 GHz Very Long Baseline Array (VLBA) radio observations taken over a 1 yr span, we present the detection of compact, highly polarized radio emission … Abstract From a series of 5 GHz Very Long Baseline Array (VLBA) radio observations taken over a 1 yr span, we present the detection of compact, highly polarized radio emission from the T6 brown dwarf WISE J112254.72+255022.2, compatible with electron cyclotron maser emission. Both the total and polarized lightcurves show variability in correspondence with a rotation period of 1.95 ± 0.03 hr. Comparison with models indicates that the quasi-steady radio emission of this brown dwarf is produced in circumpolar auroral rings, with remarkable similarity to the main-oval auroras in Jupiter. We have detected a large 100% polarized flare in one of the VLBA epochs (2022.82), which may imply the existence of active longitudes in the auroral rings with a nonaxisymmetric beaming cone radiation pattern, similar to the dusk/dawn asymmetries seen in the Jovian radio emissions. We also present a high-precision astrometric analysis of the sky motion of WISE J112254.72+255022.2, resulting in revised values of proper motion and parallax with an improvement in precision of 1 order of magnitude. The common kinematics of WISE J112254.72+255022.2 with its wide companion, the M dwarf LHS 302, is confirmed with submilliarcsecond precision, suggesting that this brown dwarf may have formed by gravitational fragmentation of the outer part of a protostellar disk around LHS 302. The astrometric analysis imposes very tight bounds on the presence of low-mass companions around WISE J112254.72+255022.2, ruling out objects more massive than Saturn. Our results strengthen the analogy between radio-emitting brown dwarfs and the magnetized planets of our solar system.

Determining the Physical Masses of Exoplanets Observed by Radial Velocity Measurements: A Review of Methods and Solutions, Results, and New Questions from Published Data

2025-06-23

A. G. Demin , V. I. Ananyeva , Alexander V. Tavrov | Solar System Research

Chemo-dynamics of the stellar component of the Sculptor dwarf galaxy. II. Dynamical properties and dark matter halo density

2025-06-23

José María Arroyo-Polonio , Raffaele Pascale , G. Battaglia +4 more | Astronomy and Astrophysics

Dwarf galaxy satellites of the Milky Way are excellent laboratories for testing dark matter (DM) models and baryonic feedback implementation in simulations. The Sculptor "classical" dwarf spheroidal galaxy, a system … Dwarf galaxy satellites of the Milky Way are excellent laboratories for testing dark matter (DM) models and baryonic feedback implementation in simulations. The Sculptor "classical" dwarf spheroidal galaxy, a system with two distinct stellar populations and high-quality data, offers a remarkable opportunity to study DM distributions in these galaxies. However, inferences from dynamical modeling in the literature have led to discrepant results. In this work, we infer the DM halo density distribution of Sculptor, applying a method based on spherically symmetric distribution functions depending on actions to fit the stellar structural and kinematic properties of Sculptor. The galaxy is represented via four components: two distinct stellar populations based on distribution functions, tracers within a fixed and dominant DM potential, and the contribution of a third stellar component that accounts for possible sources of contamination. The model-data comparison accounts for the kinematics and metallicities of individual stars rather than relying on binned profiles, allowing us to assign probabilities of membership to each star. This is the most general approach employed to date to model Sculptor, and we applied it on the largest available set of spectroscopic data, which have not been previously analyzed with this objective. We find the DM distribution of Sculptor to have a logarithmic inner slope of γ = 0.39 ^ and a scale radius of r_s = 0.79^ kpc at a 1σ confidence level. Our results show that the Sculptor DM density profile deviates from predictions of DM-only simulations at a 3σ level over a large range of radii. The dynamical-to-luminous mass ratio is around 13 at the 3D half-light radius and 154 at 2 kpc, the outermost radius with observed stars in our dataset. Our analysis suggests that the velocity distribution of Sculptor’s two main stellar components is isotropic in the center and becomes radially anisotropic in the outskirts. Additionally, we provide predictions for the projected radial and tangential velocity dispersion profiles. We also present updated DM annihilation and decay J- and D-factors, for which we find J = 18.15^ and D = 18.07^ for an angular aperture of 0.5 degrees.

Planetary edge trends. I. The inner edge-stellar mass correlation

2025-06-23

Meng-Fei Sun , Ji‐Wei Xie , Ji‐Lin Zhou +3 more | Astronomy and Astrophysics

Recent advancements in exoplanet detection have led to over 5,900 confirmed detections. The planetary systems hosting these exoplanets exhibit remarkable diversity. The position of the innermost planet (i.e., the inner … Recent advancements in exoplanet detection have led to over 5,900 confirmed detections. The planetary systems hosting these exoplanets exhibit remarkable diversity. The position of the innermost planet (i.e., the inner edge) in a planetary system provides important information about the relationship of the entire system to its host star properties, offering potentially valuable insights into planetary formation and evolution processes. In this work, based on the Kepler Data Release 25 catalog combined with LAMOST and Gaia data, we investigate the correlation between stellar mass and the inner edge position across different populations of small planets in multi-planetary systems, such as super-Earths and sub-Neptunes. By correcting for the influence of stellar metallicity and analyzing the impact of observational selection effects, we confirm the trend that as stellar mass increases, the position of the inner edge shifts outward. Our results reveal a stronger correlation between the inner edge and stellar mass (a_ in ∝ M_ ⋆ γ_1 ), with a power-law index of γ_1 = 0.6-1.1, which is larger compared to previous studies. The stronger correlation in our findings is primarily attributed to two factors: first, the metallicity correction applied in this work enhances the correlation; second, the previous use of occurrence rates to trace the inner edge weakens the observed correlation. Through comparison between observed statistical results and current theoretical models, we find that the pre-main-sequence dust sublimation radius of the protoplanetary disk best matches the observed inner edge stellar mass. Therefore, we conclude that the inner dust disk likely limits the innermost orbits of small planets, contrasting with the inner edges of hot Jupiters, which are associated with the magnetospheres of gas disks, as suggested by previous studies. This highlights that the inner edges of different planetary populations are likely regulated by distinct mechanisms.

A Survey of Model Fits to Brown Dwarf Spectra Through the L–T Sequence

2025-06-23

S. Turner , Denise C. Stephens , Conner B. Scoresby +1 more | The Astronomical Journal

Abstract We fit archival near-IR spectra of ∼300 brown dwarfs with atmosphere models from the Sonora and Phoenix groups. Using the parameters of the best-fit models as estimates for the … Abstract We fit archival near-IR spectra of ∼300 brown dwarfs with atmosphere models from the Sonora and Phoenix groups. Using the parameters of the best-fit models as estimates for the physical properties of the brown dwarfs in our sample, we have performed a survey of how brown dwarf atmospheres evolve with spectral type and temperature. We present the fit results and observed trends. We find that clouds have a more significant impact on near-IR spectra than disequilibrium chemistry, and that silicate clouds influence the near-IR spectrum through the late T types. We note where current atmosphere models are able to replicate the data and where the models and data conflict. We also categorize objects with similar spectral morphologies into families and discuss possible causes for their unique spectral traits. We identify two spectral families with morphologies that are likely indicative of binarity.

New Rotation Periods from the Kepler Bonus Background Light Curves

2025-06-23

Zachary R. Claytor , Jamie Tayar | The Astrophysical Journal

Abstract The Kepler field hosts the best-studied sample of field star rotation periods. However, due to Kepler’s large 4″ pixels, many of its light curves are at high risk of … Abstract The Kepler field hosts the best-studied sample of field star rotation periods. However, due to Kepler’s large 4″ pixels, many of its light curves are at high risk of contamination from background sources. The new Kepler Bonus Background light curves are deblended using a point-spread function algorithm, providing light curves of over 400,000 new background sources in addition to over 200,000 reanalyzed Kepler prime targets. These light curves provide the opportunity to search for new rotation periods. Here we apply a convolutional neural network trained on synthetic spot-modulated light curves to regress rotation periods from the Kepler Bonus light curves. We obtained periods for 32,159 total sources, 19,650 of which had previously been measured and 9811 of which are new periods for both Kepler prime and background sources. Our method also detected 608 pulsation frequencies from asteroseismic oscillations in red giants. We validate our Kepler prime periods against literature values and present the full period sample. We find excellent agreement with previously known literature periods, validating deep learning as a viable class of period determination methods. Comparing the periods and light curves of foreground–background pairs, we find that as many as 63% of periodic background light curves are still blended with the foreground, highlighting the limitations of the deblending technique.

Red supergiant stars in binary systems. II. Confirmation of B-type companions of red supergiants in the Small Magellanic Cloud using Hubble ultraviolet spectroscopy

2025-06-21

L.R. Patrick , D. J. Lennon , A. Schootemeijer +5 more | Astronomy and Astrophysics

Red supergiant (RSG) stars represent the final evolutionary phase of the majority of massive stars and hold a unique role in testing the physics of stellar models. Eighty-eight RSGs in … Red supergiant (RSG) stars represent the final evolutionary phase of the majority of massive stars and hold a unique role in testing the physics of stellar models. Eighty-eight RSGs in the Small Magellanic Cloud (SMC) were recently found to have an ultraviolet (UV) excess, which was attributed to a B-type companion. We present follow-up Hubble Space Telescope (HST) UV (1700 -- 3000,Å) spectroscopy for 16 of these stars to investigate the nature of the UV excess and confirm the presence of a hot companion. In all cases, we are able to confirm that the companion is a main-sequence B-type star based on the near-UV continuum. We determine effective temperatures, radii, and luminosities from fitting the UV continuum with TLUSTY models and find stellar parameters in the expected range for SMC B-type stars. We display these results on a Hertzsprung--Russell diagram and assess the previously determined stellar parameters using UV photometry alone. From this comparison, we conclude that UV photometric surveys are vital to identify such companions and that UV spectroscopy is similarly vital to characterise the hot companions. From a comparison with IUE spectra of 32 Cyg, a well-known RSG binary system in the Galaxy where the companion is embedded in the wind of the RSG, four targets display evidence of also being embedded in such a wind. The ages of seven targets, determined via the stellar parameters of the hot companions, are found to be in tension with the ages determined for the RSG. An explanation for the discrepancy could be unaccounted for binary mass-transfer or red straggler stars.

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Metallicities of 20 Million Giant Stars Based on Gaia XP Spectra

2025-06-20

Lin Yang , Haibo Yuan , Bowen Huang +7 more | The Astrophysical Journal Supplement Series

Abstract We design an uncertainty-aware cost-sensitive neural network (UA-CSNet) to estimate metallicities from dereddened and corrected Gaia BP/RP (XP) spectra for giant stars. This method accounts for both stochastic errors … Abstract We design an uncertainty-aware cost-sensitive neural network (UA-CSNet) to estimate metallicities from dereddened and corrected Gaia BP/RP (XP) spectra for giant stars. This method accounts for both stochastic errors in the input spectra and the imbalanced density distribution in [Fe/H] values. With a specialized architecture and training strategy, the UA-CSNet improves the precision of the predicted metallicities, especially for very metal-poor (VMP; [Fe/H] ≤ −2.0) stars. With the PASTEL catalog as the training sample, our model can estimate metallicities down to [Fe/H] ∼ −4. We compare our estimates with a number of external catalogs and conduct tests using star clusters, finding overall good agreement. We also confirm that our estimates for VMP stars are unaffected by carbon enhancement. Applying the UA-CSNet, we obtain reliable and precise metallicity estimates for approximately 20 million giant stars, including 360,000 VMP stars and 50,000 extremely metal-poor ([Fe/H] ≤ −3.0) stars. The resulting catalog is publicly available via the Chinese Virtual Observatory at doi: 10.12149/101604. This work highlights the potential of low-resolution spectra for metallicity estimation and provides a valuable data set for studying the formation and chemodynamical evolution of our Galaxy.

Structural and physical properties of singularity-free dark energy compact star generated by Durgapal- Bannerji potential

2025-06-20

S. K. Maurya , Einas Al Farsi , Akram Ali +2 more | International Journal of Geometric Methods in Modern Physics

Precision analysis of NGC 2158 with Gaia DR3

2025-06-20

Nasser M. Ahmed , A. L. Tadross | Scientific Reports

Abstract This research uses the third edition of the Gaia Data Release (DR3) to re-investigate the open star cluster NGC 2158. We employed the pyUPMASK Python package and HDBSCAN algorithms … Abstract This research uses the third edition of the Gaia Data Release (DR3) to re-investigate the open star cluster NGC 2158. We employed the pyUPMASK Python package and HDBSCAN algorithms to identify the cluster member stars. The key focus of this investigation is our new method of evaluating membership probability based on the radius of each shell in the studied cluster, rather than applying a single probability value to the entire cluster. We calculated all astrophysical parameters of NGC 2158-including center, cluster radius, radial density distribution, color-magnitude diagram, distance, age, and reddening-using the photometric and astrometric data from Gaia DR3. The cluster’s relaxation time, total mass, luminosity, and mass functions are computed. The components of the proper motions ( $$\mu$$ $$_{\alpha }$$ cos $$\delta$$ , $$\mu$$ $$_{\delta }$$ ), and the trigonometric parallax ( $$\varpi$$ ) are found to be $$-$$ 0.196 $$\pm$$ 0.03 , $$-$$ 1.984 $$\pm$$ 0.21 mas/yr and 0.21 $$\pm$$ 0.044 mas, respectively. According to the King model and pyUPMASK membership, we obtained 3067 $$\pm$$ 69.84 stars with a total mass of 3216.4 $$\pm$$ 59.50 $$M_{\odot }$$ . Using the PARSEC stellar isochrones fit, the mean cluster age and its relaxation time are 1.95 $$\pm$$ 0.28 Gyr and 89.0 $$\pm$$ 12.54 Myr, respectively. The cluster distance modulus and reddening are estimated to be 12.86 $$\pm$$ 0.080 , and 0.66 $$\pm$$ 0.040 mag, resulting in a distance of 3.733 $$\pm$$ 0.36 kpc. The mass function MF for the cluster under study has been constructed using a step function with two power lows, $$\alpha _1$$ and $$\alpha _2$$ , rather than the single power low suggested by Salpeter. In this cluster, the $$\alpha _1$$ and $$\alpha _2$$ are found to be $$-$$ 3.2 $$\pm$$ 0.3 and 2.52 $$\pm$$ 0.1 , respectively. The Gaia archive contains 17 stars flagged for variability, detecting 11 stars classified as eclipsing binaries. Additionally, we identified 62 member stars as blue stragglers. We utilized the galpy Python package to obtain the cluster’s kinematics and the Galactic orbital parameters using 126 stars which have radial velocities data in Gaia DR3 archive, with average value 26.1 $$\pm$$ 2.3 km/s.

NIRPS joining HARPS at ESO 3.6m. On-sky performance and science objectives

2025-06-20

F. Bouchy , R. Doyon , F. Pepe +7 more | Astronomy and Astrophysics

The Near-InfraRed Planet Searcher (NIRPS) is a high-resolution, high-stability near-infrared (NIR) spectrograph equipped with an adaptive optics (AO) system. Installed on the ESO 3.6-m telescope at La Silla Observatory, Chile, … The Near-InfraRed Planet Searcher (NIRPS) is a high-resolution, high-stability near-infrared (NIR) spectrograph equipped with an adaptive optics (AO) system. Installed on the ESO 3.6-m telescope at La Silla Observatory, Chile, it was developed to enable radial velocity (RV) measurements of low-mass exoplanets around M dwarfs and to characterise exoplanet atmospheres in the NIR. This paper provides a comprehensive design overview and characterisation of the NIRPS instrument, reporting on its on-sky performance, advising on how to carry out observations, and presenting its guaranteed time observation (GTO) programme. Intensive on-sky testing phases were conducted between November 2019 and March 2023. The instrument started its operations on 1 April 2023. The spectral range continuously covers the Y, J, and H bands from 972.4 to 1919.6,nm. The thermal control system maintains 1,mK stability over several months, thereby minimising drift. The NIRPS's AO-assisted fibre link improves coupling efficiency and offers a unique high-angular resolution capability with a fibre acceptance of only 0.4 A high spectral resolving power of R∼90,000 and R∼75,000 is provided in high-accuracy (HA) and high-efficiency (HE) modes, respectively. The overall throughput from the top of the atmosphere to the detector peaks at 13%. The RV precision, measured on the bright star Proxima with a known exoplanetary system, is cms . NIRPS and HARPS can be used simultaneously, offering unprecedented spectral coverage for spectroscopic characterisation and stellar activity mitigation. Modal noise can be aptly mitigated by the implementation of fibre stretchers and AO scanning mode. ms over several weeks. The instrument’s high throughput, particularly in the H band, offers a notable improvement over previous spectrographs, enhancing our ability to detect small exoplanets.

Open clusters in the outer disc studied with GTC/MEGARA. Auner 1 and Berkeley 102

2025-06-20

J. Carbajo-Hijarrubia , R. Carrera , F. Anders +4 more | Astronomy and Astrophysics

Open clusters provide valuable information on stellar nucleosynthesis and the chemical evolution of the Galactic disc because their age and distances can be measured more precisely than for field stars. … Open clusters provide valuable information on stellar nucleosynthesis and the chemical evolution of the Galactic disc because their age and distances can be measured more precisely than for field stars. We study the outermost parts of the Milky Way disc using open clusters as tracers. We focus on two clusters at galactocentric distances of about 14,kpc that have never been spectroscopically observed before and are located in largely unexplored regions of the Galaxy. We used medium-resolution spectra (R>18,700) obtained with the MEGARA integral-field unit (IFU) spectrograph at the 10.4,m Gran Telescopio Canarias (GTC) to study red giant star members of the clusters Auner 1 and Berkeley 102. We determined the radial velocities and atmospheric parameters for the member stars, and we updated the ages and distances for these two clusters. Finally, we measured the abundances of six chemical elements, that is, Fe, Ca, Co, Ni, Ba, and Eu. The two clusters are both old, $3.2±0.7$,Ga, are distant, d∼ 8,kpc, and are moderately affected by interstellar extinction, A_V∼ 1.3,mag, because they are located below the Galactic mid-plane Gal ∼ -0.7,kpc. The metallicities of Auner 1 Fe/H $=-0.30±0.09$, and Berkeley 102 Fe/H $=-0.35±0.06$, are compatible with the values of other open clusters that are situated at similar galactocentric radii. This suggests that the azimuthal metallicity varies little. The relative abundance ratios X/Fe also behave as expected, perhaps with the exception of Ca/Fe which appears to be slightly enhanced in both clusters, and Eu/Fe which is enhanced in Berkeley 102 Eu/Fe $=0.64±0.05$. Our results demonstrate that competitive Galactic archaeology is possible with GTC/MEGARA observations in IFU mode. The two studied objects open a new window into the chemical evolution of the outer Galactic disc. More observations of distant (in galactocentric distance and azimuth) open clusters with medium- to high-resolution instruments on 8-10m-class telescopes are needed to firmly establish the abundance trends of the outermost parts of the Galactic disc.

Model Choice Matters for Age Inference on the Red Giant Branch

2025-06-20

Leslie M. Morales , Jamie Tayar , Zachary R. Claytor | The Astrophysical Journal

Abstract Galactic archaeology relies on accurate stellar parameters to reconstruct the Galaxy's history, including information on stellar ages. While the precision of data has improved significantly in recent years, stellar … Abstract Galactic archaeology relies on accurate stellar parameters to reconstruct the Galaxy's history, including information on stellar ages. While the precision of data has improved significantly in recent years, stellar models used for age inference have not improved at a similar rate. In fact, different models yield notably different age predictions for the same observational data. In this paper, we assess the difference in age predictions of various widely used model grids for stars along the red giant branch. Using open-source software, we conduct a comparison of four different evolution grids, and we find that age estimations become less reliable if stellar mass is not known, with differences occasionally exceeding 80%. Additionally, we note significant disagreements in the models’ age estimations at nonsolar metallicity. Finally, we present a method for including theoretical uncertainties from stellar evolutionary tracks in age inferences of red giants, aimed at improving the accuracy of age estimation techniques used in the galactic archaeology community.

Deformation and Differential Rotation in Slowly Rotating Young Intermediate-mass Stars

2025-06-20

Subrata Kumar Panda , Shravan M. Hanasoge | The Astrophysical Journal

Abstract Asteroseismology, the study of stellar vibrations, is a method that can probe the structure deformation and internal rotation of stars. Salient among the seismic inferences of rotation from TESS … Abstract Asteroseismology, the study of stellar vibrations, is a method that can probe the structure deformation and internal rotation of stars. Salient among the seismic inferences of rotation from TESS observations are TIC 408165734, whose equatorial rotation rate is 10% faster than the pole, and TIC 307930890, which has significant radial shear and shows a decreasing spin rate outward through its envelope. We also measure structural deformation in 15 stars, nine of which are oblate, a finding consistent with expectations for relatively fast-rotating nonmagnetic stars. The difference between polar and equatorial radii in TIC 47639058 is 130 times larger than that for the Sun. The remaining six stars display splittings consistent with a prolate shape (surprisingly), possibly indicating the presence of equatorial toroidal magnetic fields. These inferences provide constraints for numerical simulations and new insights to guide theories of δ Scuti structure and rotation.

The Narrow Formation Pathway of Hot Saturns: Constraints on Initial Planetary Properties

2025-06-20

M. Xie , Sheng Jin , Dong-Hong Wu | The Astrophysical Journal

Abstract The observed exoplanet population exhibits a scarcity of short-period Saturn-mass planets, a phenomenon referred to as the “hot-Saturn desert.” This observational scarcity can be utilized to validate the theories … Abstract The observed exoplanet population exhibits a scarcity of short-period Saturn-mass planets, a phenomenon referred to as the “hot-Saturn desert.” This observational scarcity can be utilized to validate the theories regarding the formation and evolution of gas planets. In this study, we conduct large-scale numerical simulations to explore how the initial conditions of gas planets orbiting solar-type and M-dwarf stars influence their evolutionary trajectories in the semimajor axis versus planetary radius ( a – R ) parameter space. We generate a synthetic population of 10,000 short-period gaseous planets by systematically varying their initial planetary masses ( M p ), initial planetary luminosities ( L p ), initial core mass fractions ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">core</mml:mi> </mml:mrow> </mml:msub> </mml:math> ), and semimajor axes ( a ). Furthermore, we assume these gaseous planets have ceased orbital migration and model their long-term thermal evolution, taking into account the impacts of atmospheric evaporation. Our results show that the initial M p , L p , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">core</mml:mi> </mml:mrow> </mml:msub> </mml:math> are the dominant factors controlling radius evolution for short-period gas planets. The key to survival as a hot-Saturn analog appears to be having just the right combination of properties after gas disk dissipation: an M p below 0.5 Jupiter mass ( M Jup ), a substantial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">core</mml:mi> </mml:mrow> </mml:msub> </mml:math> of ≥30%, and relatively low L p on the order of 10 −6 solar luminosity ( L ⊙ ) or less. The survival criteria for hot-Saturn analogs align with theoretically unfavorable initial conditions of gas planets formed via core accretion scenario, naturally explaining the observed boundaries of the hot-Saturn desert.

Homogeneous Stellar Atmospheric Parameters and 22 Elemental Abundances for FGK Stars Derived from LAMOST Low-resolution Spectra with DD-PAYNE

2025-06-19

Meng Zhang , Maosheng Xiang , Yuan-Sen Ting +7 more | The Astrophysical Journal Supplement Series

Abstract A deep understanding of our Galaxy calls for detailed decomposition of its stellar populations via their chemical fingerprints. This requires precise stellar abundances of many elements for a large … Abstract A deep understanding of our Galaxy calls for detailed decomposition of its stellar populations via their chemical fingerprints. This requires precise stellar abundances of many elements for a large number of stars. Here, we present an updated catalog of stellar labels derived from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) low-resolution spectra in a physics-sensible and rigorous manner with DD-Payne , taking labels from high-resolution spectroscopy as a training set. The catalog contains atmospheric parameters for 6.4 million stars released in LAMOST DR9, and abundances for 22 elements, namely, C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Ni, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, for nearly 3.6 million stars with spectral signal-to-noise ratio (S/N) higher than 20. The [Fe/H] is valid down to ≃ −4.0, while elemental abundance ratios [X/Fe] are mostly valid for stars with [Fe/H] ≳ −2.0. Measurement errors in these labels are sensitive to and almost inversely proportional with S/N. For stars with S/N > 50, we achieved a typical error of 30 K in T eff , 0.07 dex in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mspace width="0.25em"/> <mml:mi>g</mml:mi> </mml:math> , ∼0.05 dex in abundances for most elements with atomic number smaller than Sr, and 0.1–0.2 dex for heavier elements. Homogenization to the label estimates is carried out via dedicated internal and external calibration. In particular, the nonlocal thermal equilibrium effect is corrected for the [Fe/H] estimates, the T eff is calibrated to the infrared flux method scale, and the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mspace width="0.25em"/> <mml:mi>g</mml:mi> </mml:math> is validated with asteroseismic measurements. The elemental abundances are internally calibrated using wide binaries, eliminating systematic trend with effective temperature. The catalog is publicly available.

Black in stellar astrophysics

2025-06-19

James O. Chibueze , Samaiyah Farid , India Jackson +2 more | Nature Astronomy

Probing Abundance Variations Among Multiple Stellar Populations in the Metal-poor Globular Cluster NGC 2298 Using Gemini-South/GHOST*

2025-06-19

Avrajit Bandyopadhyay , Rana Ezzeddine , Vinicius M. Placco +3 more | The Astronomical Journal

Abstract Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red-giant stars … Abstract Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red-giant stars from the metal-poor globular cluster NGC 2298 using the newly commissioned GHOST spectrograph at Gemini South. We derived stellar parameters and abundances for 36 species across 32 elements, including 16 neutron-capture elements. We find that the stars exhibit chemical anomalies among the light elements, allowing us to classify them into first generation (eight stars) and second generation (five stars). We derive a mean cluster metallicity of [Fe/H] = −1.98 ± 0.10 with no significant variation among cluster members. Most α - and Fe-peak elements display low star-to-star abundance dispersion, with notable exceptions for Sc, Ni, and Zn for which the dispersions in Sc vary significantly between stars from different generations to 2 σ levels. Similarly, among the neutron-capture elements, we observed considerable differences in dispersion for Sr and Eu among the first and second generation stars to 2 σ levels. We also confirm an intrinsic scatter beyond observational uncertainties for several elements using a maximum likelihood approach among stars from different generations. Additionally, we note an increase in [Sr/Eu] and [Ba/Eu] with [Mg/Fe] in first-generation stars indicating correlations between the productions of light r process and Mg. We find the universal r -process pattern, but with larger dispersions in the main r process than the limited- r elements. These differences in abundance dispersion, among first- and second-generation stars in NGC 2298, suggest complex and inhomogeneous early chemical enrichment processes, driven by contributions from multiple nucleosynthetic events, including massive stars and rare r -process events.

Effects of Transient Stellar Emissions on Planetary Climates of Tidally Locked Exo-Earths

2025-06-19

Howard Chen , Paolo De Luca , Assaf Hochman +1 more | The Astronomical Journal

Abstract Space weather events in exoplanetary environments sourced from transient host star emissions, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence a planet's habitability and … Abstract Space weather events in exoplanetary environments sourced from transient host star emissions, including stellar flares, coronal mass ejections, and stellar proton events, can substantially influence a planet's habitability and atmospheric evolution history. These time-dependent events may also affect our ability to measure and interpret its properties by modulating reservoirs of key chemical compounds and changing the atmosphere’s brightness temperature. The majority of previous work focusing on photochemical effects, ground-level UV dosages, and consequences on observed spectra. Here, using three-dimensional general circulation models with interactive photochemistry, we simulate the climate and chemical impacts of stellar energetic particle events and periodic enhancements of UV photons. We use statistical methods to examine their effects on synchronously rotating TRAPPIST-1e-like planets on a range of spatiotemporal scales. We find that abrupt thermospheric cooling is associated with radiative cooling of NO and CO 2 , and middle-to-lower atmospheric warming is associated with elevated infrared absorbers such as N 2 O and H 2 O. In certain regimes, in particular for climates around moderately active stars, atmospheric temperature changes are strongly affected by O 3 variability. Cumulative effects are largely determined by the flare frequency and the instantaneous effects are dependent on the flare’s spectral shape and energy. In addition to effects on planetary climate and atmospheric chemistry, we find that intense flares can energize the middle atmosphere, causing enhancements in wind velocities up to 40 m s −1 in substellar nightsides between 30 and 50 km in altitude. Our results suggest that successive, more energetic eruptive events from younger stars may be a pivotal factor in determining the atmosphere dynamics of their planets.

Accelerating Long-period Exoplanet Discovery by Combining Deep Learning and Citizen Science

2025-06-19

Shreshth A. Malik , Nora L. Eisner , Ian R. Mason +5 more | The Astronomical Journal

Abstract Automated planetary transit detection has become vital to identify and prioritize candidates for expert analysis and verification given the scale of modern telescopic surveys. Current methods for short-period exoplanet … Abstract Automated planetary transit detection has become vital to identify and prioritize candidates for expert analysis and verification given the scale of modern telescopic surveys. Current methods for short-period exoplanet detection work effectively due to periodicity in the transit signals, but a robust approach for detecting single-transit events is lacking. However, volunteer-labeled transits collected by the Planet Hunters TESS (PHT) project now provide an unprecedented opportunity to investigate a data-driven approach to long-period exoplanet detection. In this work, we train a 1D convolutional neural network to classify planetary transits using PHT volunteer scores as training data. We find that this model recovers planet candidates (TESS objects of interest; TOIs) at a precision and recall rate exceeding those of volunteers, with a 20% improvement in the area under the precision-recall curve and 10% more TOIs identified in the top 500 predictions on average per sector. Importantly, the model also recovers almost all planet candidates found by volunteers but missed by current automated methods (PHT community TOIs). Finally we retrospectively utilise the model to simulate live deployment in PHT to reprioritize candidates for analysis. We also find that multiple promising planet candidates, originally missed by PHT, would have been found using our approach, showing promise for upcoming real-world deployment.

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="d1e5956" altimg="si47.svg"><mml:mrow><mml:mi>u</mml:mi><mml:mi>v</mml:mi><mml:mi>b</mml:mi><mml:mi>y</mml:mi><mml:mo linebreak="goodbreak" linebreakstyle="after">−</mml:mo><mml:msub><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mi>β</mml:mi></mml:mrow></mml:msub><mml:mspace width="1em" class="nbsp"/></mml:mrow></mml:math> Photoelectric photometry of 65 A/F-type candidate stars in the Kepler field: Observations…

2025-06-18

L. Fox Machado , J. H. Peña , B. Smalley | New Astronomy

Long-term investigation of an open cluster Berkeley 65

2025-06-18

Tarak Chand , Saurabh Sharma , Koshvendra Singh +7 more | Frontiers in Astronomy and Space Sciences

We present a decade-long investigation of a poorly studied cluster, Berkeley 65 (Be 65), using deep optical data from the telescopes of ARIES, Nainital Observatory. We estimate its radius ( … We present a decade-long investigation of a poorly studied cluster, Berkeley 65 (Be 65), using deep optical data from the telescopes of ARIES, Nainital Observatory. We estimate its radius ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">cluster</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> = 1.6′, aspect ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 1.1), distance (2.0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:math> 0.1 kpc) and age ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 160 Myrs). A clear turn-off point at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 1.7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m6"><mml:mrow><mml:msub><mml:mrow><mml:mtext>M</mml:mtext></mml:mrow><mml:mrow><mml:mo>⊙</mml:mo></mml:mrow></mml:msub></mml:mrow></mml:math> in the mass function suggests the escape of low-mass stars, and the lower photometric mass compared to the dynamical mass indicates ongoing disruption due to external forces. Our long-baseline optical photometric data also identifies 64 periodic and 16 non-periodic stars in this region. We have presented the light curves and the classification of those variables. The periodic stars have periods ranging from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m7"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 0.05 days to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m8"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 3.00 days and amplitude ranges from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m9"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 8 mmag to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m10"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 700 mmag. The nonperiodic stars show variation from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m11"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 30 mmag to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m12"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 500 mmag. The periodic stars include main-sequence pulsating variables such as Slow Pulsating B-type, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m13"><mml:mrow><mml:mi>δ</mml:mi></mml:mrow></mml:math> Scuti, RR Lyrae, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m14"><mml:mrow><mml:mi>γ</mml:mi></mml:mrow></mml:math> Doradus. We report a detached binary system and rotating variables similar to BY Draconis-type stars exhibiting variable brightness caused by starspots, chromospheric activity, and magnetic field-related phenomena.

Linear Response of Rotating and Flattened Stellar Clusters: The Oblate Kuzmin–Kutuzov Stäckel Family

2025-06-18

Kerwann Tep , Christophe Pichon , Michael Petersen | The Astrophysical Journal

Abstract This paper investigates the linear response of a series of spheroidal stellar clusters, the Kuzmin–Kutuzov Stäackel family, which exhibit a continuous range of flattening and rotation, extending from an … Abstract This paper investigates the linear response of a series of spheroidal stellar clusters, the Kuzmin–Kutuzov Stäackel family, which exhibit a continuous range of flattening and rotation, extending from an isochrone sphere to a Toomre disk. The method successfully replicates the growing modes previously identified in published N -body simulations. It relies on the efficiency of the matrix method to quantify systematically the effects of rotation and flattening on the eigenmodes of the galaxy. We identify two types of bisymmetric instabilities for the flatter models—the so-called bending and bar-growing modes—the latter of which persists even for very round models. As anticipated, in its least unstable configurations, the system becomes flatter as its rotational speed increases. More realistic equilibria will be required to achieve a better match to the main sequence of fast–slow rotators. The corresponding code is made public.

Performance Calibration of the Wavefront Sensor’s EMCCD Detector for the Cool Planets Imaging Coronagraph Aboard CSST

2025-06-18

Jiangpei Dou , Bingli Niu , Gang Zhao +5 more | Journal of Imaging

The wavefront sensor (WFS), equipped with an electron-multiplying charge-coupled device (EMCCD) detector, is a critical component of the Cool Planets Imaging Coronagraph (CPI-C) on the Chinese Space Station Telescope (CSST). … The wavefront sensor (WFS), equipped with an electron-multiplying charge-coupled device (EMCCD) detector, is a critical component of the Cool Planets Imaging Coronagraph (CPI-C) on the Chinese Space Station Telescope (CSST). Precise calibration of the WFS's EMCCD detector is essential to meet the stringent requirements for high-contrast exoplanet imaging. This study comprehensively characterizes key performance parameters of the detector to ensure its suitability for astronomical observations. Through a multi-stage screening protocol, we identified an EMCCD chip exhibiting high resolution and low noise. The electron-multiplying gain (EM Gain) of the EMCCD was analyzed to determine its impact on signal amplification and noise characteristics, identifying the optimal operational range. Additionally, noise properties such as readout noise were investigated. Experimental results demonstrate that the optimized detector meets CPI-C's initial application requirements, achieving high resolution and low noise. This study provides theoretical and experimental foundations for the use of EMCCD-based WFS in adaptive optics and astronomical observations, ensuring their reliability for advanced space-based imaging applications.

Rings and arcs around evolved stars. IV. Characterizing the physical properties of the rings around IC 418 with MUSE

2025-06-18

B. Montoro-Molina , M. A. Guerrero , G. Ramos-Larios +3 more | Astronomy and Astrophysics

A fraction of planetary nebulae (PNe) presents ring-like features in their halos and outermost envelopes. These are thought to be the relic of the last mass loss gaps at the … A fraction of planetary nebulae (PNe) presents ring-like features in their halos and outermost envelopes. These are thought to be the relic of the last mass loss gaps at the end of the asymptotic giant branch (AGB) phase, providing information on cyclic mass-loss modulations associated either with stellar pulsations or binary interactions. We aim at characterizing the spatial and physical properties of the ring-like features around IC,418, the iconic Spirograph Nebula. Deep Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopic observations and sharp Hubble Space Telescope (HST) images have been investigated to search for the faintest arc-like features and to characterize their physical properties. Up to 10 concentric arc-like features are detected, with a notable change in the inter-ring gap, which is smaller for the innermost rings. This is interpreted as evidence of the interaction of the expanding nebula with the arc-like features, which otherwise would expand slower. The nebula proper motion also affects the shape and gap between arc-like features. The extinction radial profile decreases outward, indicating the presence of dust. Otherwise the electronic temperature (T_ e ) and density (n_ e ) derived both from emission line radial profiles and integrated spectra extracted show values around 10000 K and 8000 cm^-3, respectively. Collectively these results indicate distinct differences between the inner nebula, which is denser and more extincted, and the ring-like structures.

Testing the asteroseismic estimates of stellar radii with surface brightness--colour relations and Gaia DR3 parallaxes. III. Main-sequence stars

2025-06-18

G. Valle , M. Dell'Omodarme , P.G. Prada Moroni +1 more | Astronomy and Astrophysics

Expanding upon a recent investigation devoted to giant stars, we compare the radii derived from the asteroseismic scaling relations with those from surface brightness--colour relations (SBCRs) combined with the Gaia … Expanding upon a recent investigation devoted to giant stars, we compare the radii derived from the asteroseismic scaling relations with those from surface brightness--colour relations (SBCRs) combined with the Gaia DR3 parallaxes for main-sequence (MS) stars. The atmospheric and asteroseismic parameters were sourced from the recently released KEYSTONE catalogue and matched to Gaia DR3 and TESS Input Catalog v8.2 to obtain precise parallaxes, V- and K_S-band magnitudes, and colour excesses, E(B- V). We computed SBCR-based radii using two different SBCRs, and estimated their relative differences with respect to radius estimates from asteroseismic grid-based methods. We find a good agreement between SBCR and asteroseismic radii, with mean relative differences in radii (E_g) in the range 2% to 3% and a standard deviation of about 3%, consistent with the expected variability of SBCRs. We find no dependence on parallax, and a mild dependence on Fe/H for one of the SBCRs tested. The relative difference in the estimated radii decreases as the mass increases, leading to a negative correlation between E_g and the estimated stellar mass, with a slope varying from -0.051±0.016 to -0.039±0.014 per solar mass, depending on the chosen SBCR. This change in slope led to a roughly 1.5% larger discrepancy in the E_g estimates for stars with masses below 1.0 M_ This larger discrepancy at the low-mass end supports conclusions drawn from giant star studies. This result is independently corroborated by the LEGACY sample, which uses Kepler photometry processed with the same pipeline as KEYSTONE. For the LEGACY sample we measure a mean relative offset in E_g of -1.4% with a standard deviation of 2.3%, and a dependence of E_g on mass with a slope of -0.052±0.011 per mass unit, both fully consistent with the KEYSTONE analysis. The analysis reveals a strong agreement between SBCR-based and asteroseismic radii for MS stars, but the apparent mass dependence still requires closer examination. This result is reassuring as it demonstrates the great accuracy and reliability of the radius estimates obtained through SBCRs, which, moreover, offer the significant advantage of being applicable to a large sample of stars with substantially lower time and costs compared to what is required by asteroseismology.

Asteroseismology of the G8 subgiant β Aquilae with SONG-Tenerife, SONG-Australia and TESS

2025-06-18

H. Kjeldsen , T. R. Bedding , Yaguang Li +7 more | Astronomy and Astrophysics

We present time-series radial velocities of the G8 subgiant star obtained in 2022 and 2023 using SONG-Tenerife and for the first time SONG-Australia. We also analyse a sector of TESS … We present time-series radial velocities of the G8 subgiant star obtained in 2022 and 2023 using SONG-Tenerife and for the first time SONG-Australia. We also analyse a sector of TESS photometry that overlapped with the 2022 SONG data. We processed the time series to assign weights and to remove bad data points. The resulting power spectrum clearly shows solar-like oscillations centred at 430 The TESS light curve shows the oscillations at lower signal-to-noise, reflecting the fact that photometric measurements are much more affected by the granulation background than are radial velocities. The simultaneous observations in velocity and photometry represent the best such measurements for any star apart from the Sun. They allowed us to measure the ratio between the bolometric photometric amplitude and the velocity amplitude to be $26.6 ± 3.1$,ppm/ We measured this ratio for the Sun from published SOHO data to be $19.5 ± 0.7$,ppm/ and, after accounting for the difference in effective temperatures of and the Sun, these values align with expectations. In both the Sun and the photometry-to-velocity ratio appears to be a function of frequency. We also measured the phase shift of the oscillations in between SONG and TESS to be ∘ ± 7^ ∘ which agrees with the value for the Sun and also with a 3D simulation of a star with similar properties to Importantly for exoplanet searches, we argue that simultaneous photometry can be used to predict the contribution of oscillations to radial velocities. We measured frequencies for oscillation modes in and carried out asteroseismic modelling, yielding an excellent fit to the frequencies. We derived accurate values for the mass and age, and were able to place quite strong constraints on the mixing-length parameter. Finally, we show that the oscillation properties of are very similar to stars in the open cluster M67.

Common envelopes in massive stars. III. The obstructive role of radiation transport in envelope ejection

2025-06-17

Mike Y. M. Lau , Ryosuke Hirai , Daniel J. Price +2 more | Astronomy and Astrophysics

We present 3D radiation hydrodynamics simulations of CE evolution involving a 12 red supergiant donor and a 3 companion. Existing 3D simulations are predominantly adiabatic, focusing strongly on low-mass donors … We present 3D radiation hydrodynamics simulations of CE evolution involving a 12 red supergiant donor and a 3 companion. Existing 3D simulations are predominantly adiabatic, focusing strongly on low-mass donors on the red giant and asymptotic giant branches. However, the adiabatic assumption breaks down once the perturbed CE material becomes optically thin or when entering a longer-timescale evolutionary phase after the dynamical plunge-in. This is especially important for high-mass red supergiant donors, which have short thermal timescales, adding significant uncertainty to our understanding of how massive binary stars evolve into gravitational-wave sources, X-ray binaries, stripped-envelope supernovae, and more. We compare our radiation hydrodynamics simulations with an adiabatic simulation from Paper I that is otherwise identical, finding that radiative diffusion strongly inhibits CE ejection. The fraction of ejected mass is roughly half that of the adiabatic case without accounting for recombination energy release. Almost no material is ejected during the dynamical plunge-in, and longer-timescale ejection during the slow spiral-in is suppressed. However, the orbital separation reached at the end of the dynamical plunge-in does not differ significantly. The large amount of remaining bound mass tentatively supports the emerging view that the dynamical plunge-in is followed by a non-adiabatic phase, during which a substantial fraction of the envelope is ejected and the binary orbit may continue to evolve.

NIRCam Yells at Cloud: JWST MIRI Imaging Can Directly Detect Exoplanets of the Same Temperature, Mass, Age, and Orbital Separation as Saturn and Jupiter

2025-06-17

Rachel Bowens-Rubin , James Mang , Mary Anne Limbach +7 more | The Astrophysical Journal Letters

Abstract NIRCam and MIRI coronagraphy has successfully demonstrated the ability to directly image young sub-Jupiter-mass and mature gas giant exoplanets. However, these modes struggle to reach the sensitivities needed to … Abstract NIRCam and MIRI coronagraphy has successfully demonstrated the ability to directly image young sub-Jupiter-mass and mature gas giant exoplanets. However, these modes struggle to reach the sensitivities needed to find the population of cold giant planets that are similar to our own solar system’s giant planets ( T eff = 60–125 K, a = 5–30 au). For the first time, we explore the high-contrast imaging capabilities of MIRI imaging rather than coronagraphy. Using data from the JWST GO 6122: Cool Kids on the Block program, which targets nearby (<6 pc) M dwarfs with NIRCam coronagraphy and MIRI imaging, we demonstrate that 21 μ m MIRI imaging can detect planets with the same temperature, mass, age, and orbital separations as Saturn and Jupiter. For systems within 3 pc, 21 μ m MIRI imaging reaches the sensitivity needed to detect planets colder than Saturn (<95 K). NIRCam coronagraphy can achieve similar results only in the unlikely case that a cold giant planet is cloud-free. Motivated by these compelling findings, we extend our analysis to evaluate the measured performance of MIRI F2100W imaging versus NIRCam F444W coronagraphy to 70 pc and conclude that MIRI imaging offers the advantage for systems within 20 pc. Microlensing surveys predict an occurrence rate as high as one to two low-mass giant exoplanets per star, suggesting that JWST MIRI imaging surveys of nearby systems may be poised to uncover a substantial population. This breakthrough enables a path toward the first direct characterization of cold giant exoplanets that are analogous to the solar system giant planets.

A Tale of Dynamical Instabilities and Giant Impacts in the Exoplanet Radius Valley

2025-06-17

S. Shibata , André Izidoro | The Astrophysical Journal Letters

Abstract The size distribution of planets with radii between 1 R ⊕ and 4 R ⊕ peaks near 1.4 R ⊕ and 2.2 R ⊕ , with a dip around … Abstract The size distribution of planets with radii between 1 R ⊕ and 4 R ⊕ peaks near 1.4 R ⊕ and 2.2 R ⊕ , with a dip around 1.8 R ⊕ —the so-called “radius valley.” Recent statistical analyses suggest that planets within this valley (1.5 < R < 2 R ⊕ ) tend to have slightly higher orbital eccentricities than those outside it. The origin of this dynamical signature remains unclear. We revisit the “breaking the chains” formation model and propose that late dynamical instabilities—occurring after disk dispersal—may account for the elevated eccentricities observed in the radius valley. Our simulations show that subvalley planets ( R < 2 R ⊕ ) are generally rocky, while those beyond the valley ( R > 2 R ⊕ ) are typically water-rich. Rocky planets that undergo strong dynamical instabilities and numerous late giant impacts have their orbits excited and their radii increased, ultimately placing them into the radius valley. In contrast, the larger, water-rich planets just beyond the valley experience weaker instabilities and fewer impacts, resulting in lower eccentricities. This contrast leads to a peak in the eccentricity distribution within the valley. The extent to which planets in the radius valley are dynamically excited depends sensitively on the orbital architecture before the orbital instability. Elevated eccentricities among radius valley planets arise primarily in scenarios that form a sufficiently large number of rocky planets within 100 days (typically ≳5) prior to instability, and that also host external perturbers ( P > 100 days), which further amplify the strength of dynamical instabilities.

MG1-1995959: An Eclipsing Binary Star with a Pronounced O’Connell Effect

2025-06-17

E. R. Craine , Brian L. Craine , C. J. Corbally +7 more | The Astrophysical Journal

Abstract MG1-1995959 is a short-period (∼0.586 day) eclipsing binary, exhibiting at times an extraordinarily large O’Connell effect (OE), for which this paper reports its discovery, time series photometry, and spectroscopic … Abstract MG1-1995959 is a short-period (∼0.586 day) eclipsing binary, exhibiting at times an extraordinarily large O’Connell effect (OE), for which this paper reports its discovery, time series photometry, and spectroscopic observation. The photometry is scattered across years 2001–2023, with spectroscopic observations from 2023. Photometric curves exhibit classical OE asymmetries, whereby maxima following primary and secondary eclipses are of different magnitudes. Short time span photometric time series provide static characterizations of OE stars yielding incomplete representations of critical macrobehavior. In contrast, MG1-1995959 photometry is of sufficient duration to indicate pronounced changes in such behavior, suggesting that intense observing programs can provide key benchmark data to better inform complex modeling efforts. Spectra indicate the primary to be K1 Vk(e), and the secondary type is ∼K5 V. PHOEBE modeling of the light curve from 2014 enables estimation of key stellar parameters (primary/secondary): T eff [K] (5110/4260), and, in solar units, mass (0.86/0.68) and radius (0.93/0.65). The inclination of the system was found to be ∼78°. PHOEBE modeling of light curves from 2013, 2022, and 2023 is presented, demonstrating (1) the light curves can be well fit by invoking distributions of star spots, (2) optimal spot sizes and distributions vary dramatically as a function of time, and (3) this is a powerful tool with which to investigate the short term evolution of this star. MG1-1995959 is an accessible star with dynamic and unusual behavior deserving of intensive study to better understand nuances of the OE and the nature of late-type main-sequence stars.

Revisiting the Li Abundances of Stars with and without Detected Planets from High-resolution Spectroscopy

2025-06-17

Jingyi Qin , Hongliang Yan , Wenyuan Cui +7 more | The Astrophysical Journal

Abstract Whether the presence of planets affects the lithium (Li) abundance of their host stars is still an open question. To investigate the difference in the Li abundance between planet-host … Abstract Whether the presence of planets affects the lithium (Li) abundance of their host stars is still an open question. To investigate the difference in the Li abundance between planet-host stars (HSs) and isolated stars (ISs) with no detected planets, we analyze a large sample of stars with temperatures ranging from 4600 to 6600 K and metallicity ranging from −0.55 to +0.50. The sample consists of 279 HSs whose spectra were taken from the California-Kepler Survey, which followed up planets detected by Kepler, and 171 ISs whose spectra were taken from the Keck archive. The non–local thermodynamic equilibrium (non-LTE) effects were taken into consideration. It is found that the distributions of Li abundances in both the HS and IS groups are generally consistent with each other. This suggests that the presence of Kepler-like planets does not have a significant impact on Li depletion. We also found that the non-LTE corrections cannot be neglected for stars with A(Li) over ∼2.5 dex.

Accretion and Recovery in Giant Eruptions of Massive Stars

2025-06-17

Bhawna Mukhija , Amit Kashi | The Astrophysical Journal

Abstract Giant eruptions are episodic high-rate mass-loss events that massive stars experience in the late-stage of their evolution before exploding as a core-collapse supernova. If a giant eruption occurs in … Abstract Giant eruptions are episodic high-rate mass-loss events that massive stars experience in the late-stage of their evolution before exploding as a core-collapse supernova. If a giant eruption occurs in a binary system, the companion star can accrete part of the mass. We use numerical simulations to analyze how the companion responds to accretion and how its structure and evolution are altered. We run a grid of massive stars with masses from 20 M ⊙ to 60 M ⊙ , and accretion rates from 10 −4 to 0.1 M ⊙ yr −1 , over a duration of 20 yr. For accretion rates ≲0.01 M ⊙ yr −1 , the star remains on the hotter side of the HR diagram with a minor increase in luminosity without expanding because the accretion timescale exceeds the thermal time scale by a larger factor. Mass loss through stellar winds leads to a minor drop in luminosity shortly after the accretion phase as the star enters the recovery phase. For ≳0.01 M ⊙ yr −1 , the companion star experiences a sudden increase in luminosity by about one order of magnitude, inflates, and cools. Under the accreted gas layer, the star retains its structure and continues to eject radiation-driven wind during the recovery phase, namely the time it takes to regain equilibrium. Eventually, the accreted material mixes with the inner layers of the star and the star continues to evolve as a more massive star.

Accuracy of Analytic Potentials for Orbits of Satellites Around a Milky Way-like Galaxy: Comparison with N-Body Simulations

2025-06-17

Rubens E. G. Machado , Giovanni C. Tauil , Nicholas Schweder-Souza | Universe

To study the orbits of satellites, a galaxy can be modeled either by means of a static gravitational potential or by live N-body particles. Analytic potentials allow for fast calculations … To study the orbits of satellites, a galaxy can be modeled either by means of a static gravitational potential or by live N-body particles. Analytic potentials allow for fast calculations but are idealized and non-responsive. On the other hand, N-body simulations are more realistic but demand higher computational cost. Our goal is to characterize the regimes in which analytic potentials provide a sufficient approximation and those where N-bodies are necessary. We perform two sets of simulations, using both Gala and Gadget, in order to closely compare the orbital evolution of satellites around a Milky Way-like galaxy. Focusing on the periods when the satellite has not yet been severely disrupted by tidal forces, we find that the orbits of satellites up to 108M⊙ can be reliably computed with analytic potentials to within 5% error if they are circular or moderately eccentric. If the satellite is as massive as 109M⊙ then errors of 9% are to be expected. However, if the orbital radius is smaller than 30 kpc then the results may not be relied upon with the same accuracy beyond 1–2 Gyr.

Investigating the Colour-Magnitude Relations for White Dwarf Stars in SDSS Photometry

2025-06-16

Özcan Çalışkan , Sevinç Gökmen | Physics and Astronomy Reports

Uncertainties in Ground‐Based Visual Double Star Measures—<scp>II</scp> Accuracy of Measures

2025-06-16

Graeme L. White , Roderick R. Letchford | Astronomische Nachrichten

ABSTRACT Letchford and White 2025, Paper I, determined the uncertainties in ground‐based historic measures of double stars. In this paper, the accuracy of 26,205 ground‐based measures of 857 visual double … ABSTRACT Letchford and White 2025, Paper I, determined the uncertainties in ground‐based historic measures of double stars. In this paper, the accuracy of 26,205 ground‐based measures of 857 visual double stars, made since 1780, is determined relative to space‐based measures based on positions and proper motion from the HIPPARCOS (via ASCC) and Gaia DR3 missions. We determine the accuracy of measures for the epoch of observation, the size of the telescope, the different attached instruments, and the filter applied. We find that the accuracy of the measures is improving with time; however, the typical telescope used for double‐star observations has been, and continues to be, relatively small. Modern instrumentation such as speckle interferometry and lucky imaging has advanced the accuracy by a factor of ten over traditional micrometre measurements.

Candidate Dark Galaxy-2: Validation and Analysis of an Almost Dark Galaxy in the Perseus Cluster

2025-06-16

Dayi Li , Qing Liu , Gwendolyn M. Eadie +7 more | The Astrophysical Journal Letters

Abstract Candidate Dark Galaxy-2 (CDG-2) is a potential dark galaxy consisting of four globular clusters (GCs) in the Perseus cluster, first identified in D. Li et al. through a sophisticated … Abstract Candidate Dark Galaxy-2 (CDG-2) is a potential dark galaxy consisting of four globular clusters (GCs) in the Perseus cluster, first identified in D. Li et al. through a sophisticated statistical method. The method searched for overdensities of GCs from a Hubble Space Telescope (HST) survey targeting Perseus. Using the same HST images and new imaging data from the Euclid survey, we report the detection of extremely faint but significant diffuse emission around the four GCs of CDG-2. We thus have exceptionally strong evidence that CDG-2 is a galaxy. This is the first galaxy detected purely through its GC population. Under the conservative assumption that the four GCs make up the entire GC population, preliminary analysis shows that CDG-2 has a total luminosity of L V ,gal = 6.2 ± 3.0 × 10 6 L ⊙ and a minimum GC luminosity of L V ,GC = 1.03 ± 0.2 × 10 6 L ⊙ . Our results indicate that CDG-2 is one of the faintest galaxies having associated GCs, while at least ∼16.6% of its light is contained in its GC population. This ratio is likely to be much higher (∼33%) if CDG-2 has a canonical GC luminosity function (GCLF). In addition, if the previously observed GC-to-halo mass relations apply to CDG-2, it would have a minimum dark matter halo mass fraction of 99.94% to 99.98%. If it has a canonical GCLF, then the dark matter halo mass fraction is ≳99.99%. Therefore, CDG-2 may be the most GC dominated galaxy and potentially one of the most dark matter dominated galaxies ever discovered.

Spurious Oscillatory Signal in Kepler Eclipsing Binary Light Curves

2025-06-16

Matthew F. Knote , S. M. Caballero‐Nieves , Eric S. Perlman | Research Notes of the AAS

Abstract In our study of the O’Connell effect in Kepler eclipsing binaries, we found that some systems display a spurious oscillatory signal in their long-cadence light curves. This signal occurred … Abstract In our study of the O’Connell effect in Kepler eclipsing binaries, we found that some systems display a spurious oscillatory signal in their long-cadence light curves. This signal occurred in 12% of our sample of 258 systems. The cause of this signal is a resonance between the binary’s orbital period and Kepler’s integration time. We found that binaries that have an orbital period that is close to (within ∼1%) an integer multiple or a simple fraction of the effective long-cadence integration time of 1765.5 s displayed an oscillatory signal. In this note, we highlight this phenomenon due to its potential impact on research using Kepler data, especially the study of pulsating variable stars.

Variability Census of Legacy Catalogs. V. 11,820+ New δ Scuti and γ Doradus Stars

2025-06-16

Ai-Ying Zhou | Research Notes of the AAS

Abstract This study identifies over 3335 new δ Scuti and 8496 new γ Doradus stars. These discoveries result from the fifth phase of a variability census of A-F stars selected … Abstract This study identifies over 3335 new δ Scuti and 8496 new γ Doradus stars. These discoveries result from the fifth phase of a variability census of A-F stars selected from the legacy catalogs: PPM, HD, SAO, Bonner Durchmusterung, Córdoba Durchmusterung, and Southern Durchmusterung. Across all the five project phases, this comprehensive survey has analyzed TESS light curves for 193,940 A-F stars and identified over 14,510 δ Scuti, 18,382 γ Doradus, and 2354 eclipsing binaries (EBs), along with thousands of rotational variables. Notably, over 3900 of these variables exhibit hybrid δ Sct- γ Dor pulsations, and more than 360 EBs contain pulsating ( δ Sct or γ Dor) primary components. Using TESS data, this work has revealed a significant population of previously undetected variable stars, essential for stellar and asteroseismic studies due to their relatively bright nature.

EDEN: Exploring Disks Embedded in N-body Simulations of Milky Way–mass Halos from Symphony

2025-06-16

Yunchong Wang , Philip Mansfield , Ethan O. Nadler +4 more | The Astrophysical Journal

Abstract We investigate the impact of galactic disks on the tidal stripping of cold dark matter subhalos within Milky Way (MW)-mass halos ( M vir ∼ 10 12 M ⊙ … Abstract We investigate the impact of galactic disks on the tidal stripping of cold dark matter subhalos within Milky Way (MW)-mass halos ( M vir ∼ 10 12 M ⊙ ) using a new simulation suite, EDEN. By re-simulating 45 MW-mass zoomed-in halos from the N-body Symphony compilation with embedded disk potentials, which evolve according to star formation histories predicted by the U niverse M achine model, we self-consistently tie disk growth to halo accretion rate and significantly expand the range of disk masses and formation histories studied. We use the particle-tracking-based subhalo finder Symfind to enhance the robustness of subhalo tracking. We find that disks near the median disk-to-halo mass ratio of our sample ( M *,Disk / M vir,host = 2%) reduce subhalo peak mass functions within 100 kpc by about 10% for peak masses above 10 8 M ⊙ . Heavier, MW/M31-like disks ( M *,Disk / M vir,host ≳ 5%) lead to a reduction of more than 40%. Subhalo abundance suppression is more pronounced near halo centers, with particularly enhanced stripping for subhalos accreted over 8 Gyr ago on orbits with pericenters <100 kpc. Suppression is further amplified when disk mass is increased within fixed halo and disk assembly histories. In all cases, the suppression we measure should be interpreted as stripping below the mass resolution limit rather than complete subhalo disruption. This study reshapes our understanding of the MW’s impact on its satellites, suggesting it strips subhalos more efficiently than typical MW-mass galaxies due to its larger disk-to-halo mass ratio and earlier disk formation.

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