Physics and Astronomy › Astronomy and Astrophysics

Gamma-ray bursts and supernovae

Works Count: 94666

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Description

This cluster of papers explores the connections between gamma-ray bursts, supernovae, neutron stars, kilonova, and nucleosynthesis. It covers topics such as the physics of gamma-ray bursts, progenitors of core-collapse supernovae, electromagnetic counterparts of compact object mergers, and the association of gamma-ray bursts with supernovae. The cluster also delves into the impact of high-mass stars, gravitational waves, and type Ia supernovae on cosmic explosions.

Keywords

Gamma-Ray Bursts; Supernovae; Neutron Stars; Kilonova; Nucleosynthesis; Astrophysical Flashes; High-Mass Stars; Gravitational Waves; Type Ia Supernovae; Cosmic Explosions

Measurements of Ω and Λ from 42 High‐Redshift Supernovae

1999-06-01

S. Perlmutter , G. Aldering , G. Goldhaber +7 more

We report measurements of the mass density, ΩM, and cosmological-constant energy density, ΩΛ, of the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology … We report measurements of the mass density, ΩM, and cosmological-constant energy density, ΩΛ, of the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 and 0.83, are fitted jointly with a set of supernovae from the Calán/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All supernova peak magnitudes are standardized using a SN Ia light-curve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8ΩM-0.6ΩΛ≈-0.2±0.1 in the region of interest (ΩM≲1.5). For a flat (ΩM+ΩΛ=1) cosmology we find ΩMflat=0.28+0.09-0.08 (1 σ statistical) +0.05-0.04 (identified systematics). The data are strongly inconsistent with a Λ=0 flat cosmology, the simplest inflationary universe model. An open, Λ=0 cosmology also does not fit the data well: the data indicate that the cosmological constant is nonzero and positive, with a confidence of P(Λ>0)=99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t0flat=14.9+1.4-1.1(0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calán/Tololo sample and our high-redshift sample. Excluding those few supernovae that are outliers in color excess or fit residual does not significantly change the results. The conclusions are also robust whether or not a width-luminosity relation is used to standardize the supernova peak magnitudes. We discuss and constrain, where possible, hypothetical alternatives to a cosmological constant.

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An unusual supernova in the error box of the γ-ray burst of 25 April 1998

1998-10-01

T. J. Galama , P. M. Vreeswijk , J. van Paradijs +7 more

On the Normalization of the Cosmic Star Formation History

2006-10-27

Andrew Hopkins , J. F. Beacom

Strong constraints on the cosmic star formation history (SFH) have recently been established using ultraviolet and far-infrared measurements, refining the results of numerous measurements over the past decade. Taken together, … Strong constraints on the cosmic star formation history (SFH) have recently been established using ultraviolet and far-infrared measurements, refining the results of numerous measurements over the past decade. Taken together, the most recent and robust data indicate a compellingly consistent picture of the SFH out to redshift z~6, with especially tight constraints for z<~1. We fit these data with simple analytical forms, and derive conservative bands to indicate possible variations from the best fits. Since the z<~1 SFH data are quite precise, we investigate the sequence of assumptions and corrections that together affect the SFH normalisation, to test their accuracy, both in this redshift range and beyond. As lower limits on this normalisation, we consider the evolution in stellar mass density, metal mass density, and supernova rate density, finding it unlikely that the SFH normalisation is much lower than indicated by our direct fit. Additionally, predictions from the SFH for supernova type Ia rate densities tentatively suggests delay times of ~3 Gyr. As a corresponding upper limit on the SFH normalisation, we consider the Super-Kamiokande (SK) limit on the electron antineutrino flux from past core-collapse supernovae, which applies primarily to z<~1. We find consistency with the SFH only if the neutrino temperatures from SN events are relatively modest. Constraints on the assumed initial mass function (IMF) also become apparent. The traditional Salpeter IMF, assumed for convenience by many authors, is known to be a poor representation at low stellar masses (<~ 1 solar mass), and we show that recently favoured IMFs are also constrained. In particular, somewhat shallow, or top-heavy, IMFs may be preferred, although they cannot be too top-heavy. (Abridged)

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Identification of two classes of gamma-ray bursts

1993-08-01

C. Kouveliotou , Charles A. Meegan , G. J. Fishman +5 more

view Abstract Citations (1679) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Identification of Two Classes of Gamma-Ray Bursts Kouveliotou, Chryssa ; Meegan, Charles A. ; … view Abstract Citations (1679) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Identification of Two Classes of Gamma-Ray Bursts Kouveliotou, Chryssa ; Meegan, Charles A. ; Fishman, Gerald J. ; Bhat, Narayana P. ; Briggs, Michael S. ; Koshut, Thomas M. ; Paciesas, William S. ; Pendleton, Geoffrey N. Abstract We have studied the duration distribution of the gamma-ray bursts of the first BATSE catalog. We find a bimodality in the distribution, which separates GRBs into two classes: short events (less than 2 s) and longer ones (more than 2 s). Both sets are distributed isotropically and inhomogeneously in the sky. We find that their durations are anticorrelated with their spectral hardness ratios: short GRBs are predominantly harder, and longer ones tend to be softer. Our results provide a first GRB classification scheme based on a combination of the GRB temporal and spectral properties. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/186969 Bibcode: 1993ApJ...413L.101K Keywords: Astronomical Catalogs; Gamma Ray Bursts; Gamma Ray Observatory; Frequency Distribution; Spatial Distribution; Transient Response; Space Radiation; GAMMA RAYS: BURSTS full text sources ADS |

The absolute magnitudes of Type IA supernovae

1993-08-01

M. M. Phillips

view Abstract Citations (1716) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Absolute Magnitudes of Type IA Supernovae Phillips, M. M. Abstract Absolute magnitudes in … view Abstract Citations (1716) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Absolute Magnitudes of Type IA Supernovae Phillips, M. M. Abstract Absolute magnitudes in the B, V, and I bands are derived for nine well-observed Type Ia supernovae using host galaxy distances estimated via the surface brightness fluctuations or Tully-Fisher methods. These data indicate that there is a significant intrinsic dispersion in the absolute magnitudes at maximum light of Type Ia supernovae, amounting to +/- 0.8 mag in B, +/- 0.6 mag in V, and +/- 0.5 mag in I. Moreover, the absolute magnitudes appear to be tightly correlated with the initial rate of decline of the B light curve, with the slope of the correlation being steepest in B and becoming progressively flatter in the V and I bands. This implies that the intrinsic B - V colors of Type Ia supernovae at maximum light are not identical, with the fastest declining light curves corresponding to the intrinsically reddest events. Certain spectroscopic properties may also be correlated with the initial decline rate. These results are most simply interpreted as evidence for a range of progenitor masses, although variations in the explosion mechanism are also possible. Considerable care must be exercised in employing Type Ia supernovae as cosmological standard candles, particularly at large redshifts where Malmquist bias could be an important effect. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/186970 Bibcode: 1993ApJ...413L.105P Keywords: Light Curve; Stellar Magnitude; Supernovae; White Dwarf Stars; Astronomical Photometry; Brightness Distribution; Stellar Luminosity; Astrophysics; COSMOLOGY: DISTANCE SCALE; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (18) NED (18)

The Nucleosynthetic Signature of Population III

2002-03-01

Alexander Heger , S. E. Woosley

Growing evidence suggests that the first generation of stars may have been quite massive (~100-300 M☉). Could these stars have left a distinct nucleosynthetic signature? We explore the nucleosynthesis of … Growing evidence suggests that the first generation of stars may have been quite massive (~100-300 M☉). Could these stars have left a distinct nucleosynthetic signature? We explore the nucleosynthesis of helium cores in the mass range MHe = 64-133 M☉, corresponding to main-sequence star masses of approximately 140-260 M☉. Above MHe = 133 M☉, without rotation and using current reaction rates, a black hole is formed, and no nucleosynthesis is ejected. For lighter helium core masses, ~40-63 M☉, violent pulsations occur, induced by the pair instability and accompanied by supernova-like mass ejection, but the star eventually produces a large iron core in hydrostatic equilibrium. It is likely that this core, too, collapses to a black hole, thus cleanly separating the heavy-element nucleosynthesis of pair instability supernovae from those of other masses, both above and below. Indeed, black hole formation is a likely outcome for all Population III stars with main-sequence masses between about 25 and 140 M☉ (MHe = 9-63 M☉) as well as those above 260 M☉. Nucleosynthesis in pair instability supernovae varies greatly with the mass of the helium core. This core determines the maximum temperature reached during the bounce. At the upper range of exploding core masses, a maximum of 57 M☉ of 56Ni is produced, making these the most energetic and the brightest thermonuclear explosions in the universe. Integrating over a distribution of masses, we find that pair instability supernovae produce a roughly solar distribution of nuclei having even nuclear charge (Si, S, Ar, etc.) but are remarkably deficient in producing elements with odd nuclear charge—Na, Al, P, V, Mn, etc. This is because there is no stage of stable post-helium burning to set the neutron excess. Also, essentially no elements heavier than zinc are produced owing to a lack of s- and r-processes. The Fe/Si ratio is quite sensitive to whether the upper bound on the initial mass function is over 260 M☉ or somewhere between 140 and 260 M☉. When the yields of pair instability supernovae are combined with reasonable estimates of the nucleosynthesis of Population III stars from 12 to 40 M☉, this distinctive pattern of deficient production of odd-Z elements persists. Some possible strategies for testing our predictions are discussed.

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Nucleosynthesis in Chandrasekhar Mass Models for Type Ia Supernovae and Constraints on Progenitor Systems and Burning‐Front Propagation

1999-12-01

Koichi Iwamoto , F. Brachwitz , Ken' ichi Nomoto +4 more

The major uncertainties involved in the Chandrasekhar mass models for Type Ia supernovae (SNe Ia) are related to the companion star of their accreting white dwarf progenitor (which determines the … The major uncertainties involved in the Chandrasekhar mass models for Type Ia supernovae (SNe Ia) are related to the companion star of their accreting white dwarf progenitor (which determines the accretion rate and consequently the carbon ignition density) and the flame speed after the carbon ignition. We calculate explosive nucleosynthesis in relatively slow deflagrations with a variety of deflagration speeds and ignition densities to put new constraints on the above key quantities. The abundance of the Fe group, in particular of neutron-rich species like 48Ca,50Ti,54Cr,54,58Fe, and 58Ni, is highly sensitive to the electron captures taking place in the central layers. The yields obtained from such a slow central deflagration, and from a fast deflagration or delayed detonation in the outer layers, are combined and put to comparison with solar isotopic abundances. To avoid excessively large ratios of 54Cr/56Fe and 50Ti/56Fe, the central density of the "average" white dwarf progenitor at ignition should be as low as ≲2 × 109 g cm-3. To avoid the overproduction of 58Ni and 54Fe, either the flame speed should not exceed a few percent of the sound speed in the central low Ye layers or the metallicity of the average progenitors has to be lower than solar. Such low central densities can be realized by a rapid accretion as fast asimg1.gif ≳ 1 × 10-7 M☉ yr-1. In order to reproduce the solar abundance of 48Ca, one also needs progenitor systems that undergo ignition at higher densities. Even the smallest laminar flame speeds after the low-density ignitions would not produce sufficient amount of this isotope. We also found that the total amount of 56Ni, the Si-Ca/Fe ratio, and the abundance of some elements like Mn and Cr (originating from incomplete Si burning), depend on the density of the deflagration-detonation transition in delayed detonations. Our nucleosynthesis results favor transition densities slightly below 2.2 × 107 g cm-3.

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Accreting white dwarf models of Type I supernovae. III - Carbon deflagration supernovae

1984-11-01

K. Nomoto , F.‐K. Thielemann , K. Yokoi

view Abstract Citations (1442) References (91) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accreting white dwarf models for type I supern. III. Carbon deflagration supernovae. Nomoto, K. … view Abstract Citations (1442) References (91) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accreting white dwarf models for type I supern. III. Carbon deflagration supernovae. Nomoto, K. ; Thielemann, F. -K. ; Yokoi, K. Abstract The carbon deflagration models in accreting C + O white dwarfs are presented as a plausible model for Type I supernovae. The evolution of the white dwarf is calculated from the beginning of accretion. The relatively rapid accretion studied here (Mdot > 4 x 10-8 Msun yr-1) leads to the initiation of the carbon deflagration at the center. Subsequent propagation of the convective carbon deflagration wave and associated explosive nucleosynthesis are calculated for several cases of mixing length in the convection theory. The deflagration wave synthesizes 0.5-0.6 Msun 56Ni in the inner layer of the star; this amount is sufficient to power the light curve of Type I supernovae by the radioactive decays of 56Ni and 56Co. In the outer layers, substantial amount of intermediate mass elements, Ca, Ar, S, Si, Mg, and O are synthesized in the decaying deflagration wave; this is consistent with the spectra of Type I supernovae near maximum light. As a result of large nuclear energy release, the star is disrupted completely, leaving no compact star remnant behind. Thus the carbon deflagration model can account for many of the observed features of Type I supernovae. Nucleosynthesis in the deflagration models is discussed based on the reaction network calculation including 205 species: The abundance ratios of these species with respect to 56Fe normalized to the solar values are shown. These ratios are ∼1 for 40Ca and ∼0.5 for 36Ar, 32S, and 28Si. This suggests that Type I supernovae produce a significant fraction of these elements in the Galaxy besides iron peak elements, which may be complementary to the nucleosynthesis in massive star models for Type II supernovae. The production of neutronrich isotopes, γ-radioactivities, and 5- and r-process elements are discussed. Finally, the light curves and early time spectra based on the present models are compared with Type I supernova observations. Publication: The Astrophysical Journal Pub Date: November 1984 DOI: 10.1086/162639 Bibcode: 1984ApJ...286..644N Keywords: Carbon Stars; Deflagration; Nuclear Fusion; Stellar Mass Accretion; Supernovae; White Dwarf Stars; Hydrodynamics; Light Curve; Neutrinos; Stellar Composition; Stellar Models; Wave Propagation; Astrophysics full text sources ADS | data products SIMBAD (1) Related Materials (3) Part 1: 1982ApJ...253..798N Part 2: 1982ApJ...257..780N Part 4: 1985ApJ...294..619B

The Swift X-Ray Telescope

2005-10-01

D. N. Burrows , J. E. Hill , J. A. Nousek +7 more

The physics of gamma-ray bursts

2005-01-28

Tsvi Piran

Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space … Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding of GRB's, showing that they are cosmological, that they are accompanied by long-lasting afterglows, and that they are associated with core-collapse supernovae. At the same time a theoretical understanding has emerged in the form of the fireball internal-external shocks model. According to this model GRB's are produced when the kinetic energy of an ultrarelativistic flow is dissipated in internal collisions. The afterglow arises when the flow is slowed down by shocks with the surrounding circumburst matter. This model has had numerous successful predictions, like the predictions of the afterglow itself, of jet breaks in the afterglow light curve, and of the optical flash that accompanies the GRB's. This review focuses on the current theoretical understanding of the physical processes believed to take place in GRB's.

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Gamma-ray bursts from stellar mass accretion disks around black holes

1993-03-01

S. E. Woosley

view Abstract Citations (2128) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-Ray Bursts from Stellar Mass Accretion Disks around Black Holes Woosley, S. E. Abstract … view Abstract Citations (2128) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-Ray Bursts from Stellar Mass Accretion Disks around Black Holes Woosley, S. E. Abstract A cosmological model for gamma-ray bursts is explored in which the radiation is produced as a broadly beamed pair fireball along the rotation axis of an accreting black hole. The black hole may be a consequence of neutron star merger or neutron star-black hole merger, but for long complex bursts, it is more likely to come from the collapse of a single Wolf-Rayet star endowed with rotation ('failed' Type Ib supernova). The disk is geometrically thick and typically has a mass inside 100 km of several tenths of a solar mass. In the failed supernova case, the disk is fed for a longer period of time by the collapsing star. At its inner edge the disk is thick to its own neutrino emission and evolves on a viscous time scale of several seconds. In a region roughly 30 km across, interior to the accretion disk and along its axis of rotation, a pair fireball is generated by neutrino annihilation and electron-neutrino scattering which deposit approximately 10 exp 50 ergs/s. Publication: The Astrophysical Journal Pub Date: March 1993 DOI: 10.1086/172359 Bibcode: 1993ApJ...405..273W Keywords: Accretion Disks; Black Holes (Astronomy); Gamma Ray Bursts; Stellar Evolution; Stellar Mass Accretion; Stellar Physics; Astronomical Models; Supernovae; Wolf-Rayet Stars; Space Radiation; ACCRETION; ACCRETION DISKS; BLACK HOLE PHYSICS; GAMMA RAYS: BURSTS; STARS: EVOLUTION; STARS: SUPERNOVAE: GENERAL full text sources ADS |

The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters

1995-09-01

R. H. Becker , R. L. White , D. J. Helfand

view Abstract Citations (2408) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters Becker, Robert … view Abstract Citations (2408) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The FIRST Survey: Faint Images of the Radio Sky at Twenty Centimeters Becker, Robert H. ; White, Richard L. ; Helfand, David J. Abstract The FIRST survey to produce Faint Images of the Radio Sky at Twenty centimeters is now underway using the NRAO Very Large Array. We describe here the scientific motivation for a large-area sky survey at radio frequencies which has a sensitivity and angular resolution comparable to the Palomar Observatory Sky Survey, and we recount the history that led to the current survey project. The technical design of the survey is covered in detail, including a description and justification of the grid pattern chosen, the rationale behind the integration time and angular resolution selected, and a summary of the other considerations which informed our planning for the project. A comprehensive description of the automated data analysis pipeline we have developed is presented. We also report here the results of the first year of FIRST observations. A total of 144 hr of time in 1993 April and May was used for a variety of tests, as well as to cover an initial strip of the survey extending between 07h 15m and 16h 30m in a 2°.8 wide declination zone passing through the local zenith (28.2 <δ < 31.0). A total of 2153 individual pointings yielded an image database containing 1039 merged images 46'.5 × 34'.5 in extent with 1".8 pixels and a typical rms of 0.13 mJy. A catalog derived from this 300 deg2 region contains 28,000 radio sources. We have performed extensive tests on the images and source list in order to establish the photometric and astrometric accuracy of these data products. We find systematic astrometric errors of < 0".05 individual sources down to the 1 mJy survey flux density threshold have 90% confidence error circles with radii of < 1". CLEAN bias introduces a systematic underestimate of point-source flux densities of ∼0.25 mJy; the bias is more severe for extended sources. Nonetheless, a comparison with a published deep survey field demonstrates that we successfully detect 39/49 sources with integrated flux densities greater than 0.75 mJy, including 19 of 20 sources above 2.0 mJy; the sources not detected are known to be very extended and so have surface brightnesses well below our threshold. With 480 hr of observing time committed for each of the next three B-configuration periods, FIRST will complete nearly one-half of its goal of covering the 10,000 deg2 of the north Galactic cap scheduled for inclusion in the Sloan Digital Sky Survey. All of the FIRST data raw visibilities, self-calibrated UV data sets, individual pointing maps, final merged images, source catalogs, and individual source images are being placed in the public domain as soon as they are verified; all of the 1993 data are now available through the NRAO and/or the STScI archive. We conclude with a brief summary of the scientific significance of FIRST, which represents an improvement by a factor of 50 in both angular resolution and sensitivity over the best available large area radio surveys. Publication: The Astrophysical Journal Pub Date: September 1995 DOI: 10.1086/176166 Bibcode: 1995ApJ...450..559B Keywords: RADIO CONTINUUM: GENERAL; SURVEYS full text sources ADS | data products NED (7) SIMBAD (2)

BATSE observations of gamma-ray burst spectra. I - Spectral diversity

1993-08-01

D. L. Band , J. L. Matteson , Linda Ford +7 more

view Abstract Citations (1971) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS BATSE Observations of Gamma-Ray Burst Spectra. I. Spectral Diversity Band, D. ; Matteson, J. … view Abstract Citations (1971) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS BATSE Observations of Gamma-Ray Burst Spectra. I. Spectral Diversity Band, D. ; Matteson, J. ; Ford, L. ; Schaefer, B. ; Palmer, D. ; Teegarden, B. ; Cline, T. ; Briggs, M. ; Paciesas, W. ; Pendleton, G. ; Fishman, G. ; Kouveliotou, C. ; Meegan, C. ; Wilson, R. ; Lestrade, P. Abstract We studied the time-averaged gamma-ray burst spectra accumulated by the spectroscopy detectors of the Burst and Transient Source Experiment (BATSE). The spectra are described well at low energy by a power-law continuum with an exponential cutoff N_E_(E) is proportional to Ealpha^ exp (- E/E_0_), and by a steeper power law, N_E_(E) is proportional to Ebeta^ with α > β at high energy. However, the spectral parameters α, β, and E_0_ vary from burst to burst with no universal values. The break in the spectrum, E_0_, ranges from below 100 keV to more than 1 MeV, but peaks below 200 keV with only a small fraction of the spectra breaking above 400 keV. Consequently, it is unlikely that a majority of the burst spectra are shaped directly by pair processes, unless bursts originate from a broad redshift range. We find that the correlations among burst parameters do not fulfill the predictions of the cosmological models of burst origin, but our burst sample may not be appropriate for such a test. No correlations with burst morphology or the spatial distribution were found. We also studied the process of fitting the BATSE spectral data. For example, we demonstrate the importance of using a complete spectral description even if a partial description (e.g., a model without a high-energy tail) is statistically satisfactory. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/172995 Bibcode: 1993ApJ...413..281B Keywords: Galactic Halos; Gamma Ray Bursts; Gamma Ray Spectra; Statistical Analysis; Radiation Distribution; Transient Response; Space Radiation; GAMMA RAYS: BURSTS; RADIATION MECHANISMS: MISCELLANEOUS full text sources ADS | data products SIMBAD (54) NED (38) HEASARC (1) Related Materials (3) Part 2: 1995ApJ...439..307F Part 3: 1996ApJ...473..310P Part 4: 1998ApJ...496..849P

The evolution and explosion of massive stars

2002-11-07

S. E. Woosley , Alexander Heger , T. A. Weaver

Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose composition evolves as energy is lost to radiation and neutrinos. Unlike lower-mass stars $(M\ensuremath{\lesssim}{8M}_{\ensuremath{\bigodot}}),$ however, no point is … Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose composition evolves as energy is lost to radiation and neutrinos. Unlike lower-mass stars $(M\ensuremath{\lesssim}{8M}_{\ensuremath{\bigodot}}),$ however, no point is ever reached at which a massive star can be fully supported by electron degeneracy. Instead, the center evolves to ever higher temperatures, fusing ever heavier elements until a core of iron is produced. The collapse of this iron core to a neutron star releases an enormous amount of energy, a tiny fraction of which is sufficient to explode the star as a supernova. The authors examine our current understanding of the lives and deaths of massive stars, with special attention to the relevant nuclear and stellar physics. Emphasis is placed upon their post-helium-burning evolution. Current views regarding the supernova explosion mechanism are reviewed, and the hydrodynamics of supernova shock propagation and ``fallback'' is discussed. The calculated neutron star masses, supernova light curves, and spectra from these model stars are shown to be consistent with observations. During all phases, particular attention is paid to the nucleosynthesis of heavy elements. Such stars are capable of producing, with few exceptions, the isotopes between mass 16 and 88 as well as a large fraction of still heavier elements made by the $r$ and $p$ processes.

Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples

2014-05-26

M. Betoule , R. Keßler , J. Guy +7 more

Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< … Aims. We present cosmological constraints from a joint analysis of type Ia supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z< 0.1), all three seasons from the SDSS-II (0.05 <z< 0.4), and three years from SNLS (0.2 <z< 1), and it totals 740 spectroscopically confirmed type Ia supernovae with high-quality light curves.

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Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

1998-09-01

Adam G. Riess , A. V. Filippenko , P. Challis +7 more

We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 ≤ z ≤ 0.62. The luminosity distances of these objects are determined … We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 ≤ z ≤ 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H0), the mass density (ΩM), the cosmological constant (i.e., the vacuum energy density, ΩΛ), the deceleration parameter (q0), and the dynamical age of the universe (t0). The distances of the high-redshift SNe Ia are, on average, 10%–15% farther than expected in a low mass density (ΩM = 0.2) universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant (i.e., ΩΛ > 0) and a current acceleration of the expansion (i.e., q0 < 0). With no prior constraint on mass density other than ΩM ≥ 0, the spectroscopically confirmed SNe Ia are statistically consistent with q0 < 0 at the 2.8 σ and 3.9 σ confidence levels, and with ΩΛ > 0 at the 3.0 σ and 4.0 σ confidence levels, for two different fitting methods, respectively. Fixing a "minimal" mass density, ΩM = 0.2, results in the weakest detection, ΩΛ > 0 at the 3.0 σ confidence level from one of the two methods. For a flat universe prior (ΩM + ΩΛ = 1), the spectroscopically confirmed SNe Ia require ΩΛ > 0 at 7 σ and 9 σ formal statistical significance for the two different fitting methods. A universe closed by ordinary matter (i.e., ΩM = 1) is formally ruled out at the 7 σ to 8 σ confidence level for the two different fitting methods. We estimate the dynamical age of the universe to be 14.2 ± 1.7 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely effect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these effects appear to reconcile the data with ΩΛ = 0 and q0 ≥ 0.

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Gamma-ray bursters at cosmological distances

1986-09-01

B. Paczyński

view Abstract Citations (1425) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-ray bursters at cosmological distances Paczynski, B. Abstract It is proposed that some, perhaps … view Abstract Citations (1425) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gamma-ray bursters at cosmological distances Paczynski, B. Abstract It is proposed that some, perhaps most, gamma-ray bursters are at cosmological distances, like quasars, with a redshift of about 1 or 2. This proposition requires a release of supernova-like energy of about 10 to the 51st ergs within less than 1 s, making gamma-ray bursters the brightest objects known in the universe, many orders of magnitude brighter than any quasars. This power must drive a highly relativistic outflow of electron-positron plasma and radiation from the source. It is proposed that three gamma-ray bursts, all with identical spectra, detected from B1900 + 14 by Mazets, Golenetskii, and Gur'yan and reported in 1979, were all due to a single event multiply imaged by a gravitational lens. The time intervals between the successive bursts, 10 hr to 3 days, were due to differences in the light travel time for different images. Publication: The Astrophysical Journal Pub Date: September 1986 DOI: 10.1086/184740 Bibcode: 1986ApJ...308L..43P Keywords: Astronomical Models; Cosmology; Distance; Gamma Ray Bursts; Gravitational Lenses; Black Body Radiation; Electron-Positron Plasmas; Galactic Radiation; Temporal Distribution; Astrophysics full text sources ADS | data products SIMBAD (3)

Collapsars: Gamma‐Ray Bursts and Explosions in “Failed Supernovae”

1999-10-10

Andrew MacFadyen , S. E. Woosley

Using a two-dimensional hydrodynamics code (PROMETHEUS), we explore the continued evolution of rotating helium stars, Mα ≳ 10 M☉, in which iron-core collapse does not produce a successful outgoing shock … Using a two-dimensional hydrodynamics code (PROMETHEUS), we explore the continued evolution of rotating helium stars, Mα ≳ 10 M☉, in which iron-core collapse does not produce a successful outgoing shock but instead forms a black hole of 2-3 M☉. The model explored in greatest detail is the 14 M☉ helium core of a 35 M☉ main-sequence star. The outcome is sensitive to the angular momentum. For j16 ≡ j/(1016 cm2 s-1) ≲ 3, material falls into the black hole almost uninhibited. No outflows are expected. For j16 ≳ 20, the infalling matter is halted by centrifugal force outside 1000 km where neutrino losses are negligible. The equatorial accretion rate is very low, and explosive oxygen burning may power a weak equatorial explosion. For 3 ≲ j16 ≲ 20, however, a reasonable value for such stars, a compact disk forms at a radius at which the gravitational binding energy can be efficiently radiated as neutrinos or converted to beamed outflow by magnetohydrodynamical (MHD) processes. These are the best candidates for producing gamma-ray bursts (GRBs). Here we study the formation of such a disk, the associated flow patterns, and the accretion rate for disk viscosity parameter α ≈ 0.001 and 0.1. Infall along the rotational axis is initially uninhibited, and an evacuated channel opens during the first few seconds. Meanwhile the black hole is spun up by the accretion (to a ≈ 0.9), and energy is dissipated in the disk by MHD processes and radiated by neutrinos. For the α = 0.1 model, appreciable energetic outflows develop between polar angles of 30° and 45°. These outflows, powered by viscous dissipation in the disk, have an energy of up to a few times 1051 ergs and a mass ~1 M☉ and are rich in 56Ni. They constitute a supernova-like explosion by themselves. Meanwhile accretion through the disk is maintained for approximately 10-20 s but is time variable (±30%) because of hydrodynamical instabilities at the outer edge in a region where nuclei are experiencing photodisintegration. Because the efficiency of neutrino energy deposition is sensitive to the accretion rate, this instability leads to highly variable energy deposition in the polar regions. Some of this variability, which has significant power at 50 ms and overtones, may persist in the time structure of the burst. During the time followed, the average accretion rate for the standard α = 0.1 and j16 = 10 model is 0.07 M☉ s-1. The total energy deposited along the rotational axes by neutrino annihilation is (1-14) × 1051 ergs, depending upon the evolution of the Kerr parameter and uncertain neutrino efficiencies. Simulated deposition of energy in the polar regions, at a constant rate of 5 × 1050 ergs s-1 per pole, results in strong relativistic outflow jets beamed to about 1% of the sky. These jets may be additionally modulated by instabilities in the sides of the "nozzle" through which they flow. The jets blow aside the accreting material, remain highly focused, and are capable of penetrating the star in ~10 s. After the jet breaks through the surface of the star, highly relativistic flow can emerge. Because of the sensitivity of the mass ejection and jets to accretion rate, angular momentum, and disk viscosity, and the variation of observational consequences with viewing angle, a large range of outcomes is possible, ranging from bright GRBs like GRB 971214 to faint GRB-supernovae like SN 1998bw. X-ray precursors are also possible as the jet first breaks out of the star. While only a small fraction of supernovae make GRBs, we predict that collapsars will always make supernovae similar to SN 1998bw. However, hard, energetic GRBs shorter than a few seconds will be difficult to produce in this model and may require merging neutron stars and black holes for their explanation.

How Massive Single Stars End Their Life

2003-07-01

Alexander Heger , Chris L. Fryer , S. E. Woosley +2 more

How massive stars die—what sort of explosion and remnant each produces—depends chiefly on the masses of their helium cores and hydrogen envelopes at death. For single stars, stellar winds are … How massive stars die—what sort of explosion and remnant each produces—depends chiefly on the masses of their helium cores and hydrogen envelopes at death. For single stars, stellar winds are the only means of mass loss, and these are a function of the metallicity of the star. We discuss how metallicity, and a simplified prescription for its effect on mass loss, affects the evolution and final fate of massive stars. We map, as a function of mass and metallicity, where black holes and neutron stars are likely to form and where different types of supernovae are produced. Integrating over an initial mass function, we derive the relative populations as a function of metallicity. Provided that single stars rotate rapidly enough at death, we speculate on stellar populations that might produce gamma-ray bursts and jet-driven supernovae.

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OPTICAL SPECTRA OF SUPERNOVAE

1997-09-01

A. V. Filippenko

▪ Abstract The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined … ▪ Abstract The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined by the presence of hydrogen, and they exhibit a very wide variety of photometric and spectroscopic properties. Among hydrogen-deficient SNe (Type I), three subclasses are now known: those whose early-time spectra show strong Si II (Ia), prominent He I (Ib), or neither Si II nor He I (Ic). The late-time spectra of SNe Ia consist of a multitude of blended emission lines of iron-group elements; in sharp contrast, those of SNe Ib and SNe Ic (which are similar to each other) are dominated by several relatively unblended lines of intermediate-mass elements. Although SNe Ia, which result from the thermonuclear runaway of white dwarfs, constitute a rather homogeneous subclass, important variations in their photometric and spectroscopic properties are undeniably present. SNe Ib/Ic probably result from core collapse in massive stars largely stripped of their hydrogen (Ib) and helium (Ic) envelopes, and hence they are physically related to SNe II. Indeed, the progenitors of some SNe II seem to have only a low-mass skin of hydrogen; their spectra gradually evolve to resemble those of SNe Ib. In addition to the two well-known photometric subclasses (linear and plateau) of SNe II, which may exhibit minor spectroscopic differences, there is a new subclass (SNe IIn) distinguished by relatively narrow emission lines with little or no P Cygni absorption component and slowly declining light curves. These objects probably have unusually dense circumstellar gas with which the ejecta interact.

NewHubble Space TelescopeDiscoveries of Type Ia Supernovae atz≥ 1: Narrowing Constraints on the Early Behavior of Dark Energy

2007-04-06

Adam G. Riess , L. Strolger , Stefano Casertano +7 more

We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last … We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion yr. These objects, which include 13 spectroscopically confirmed SNe Ia at z ≥ 1, were discovered during 14 epochs of reimaging of the GOODS fields North and South over 2 yr with the Advanced Camera for Surveys on HST. Together with a recalibration of our previous HST-discovered SNe Ia, the full sample of 23 SNe Ia at z ≥ 1 provides the highest redshift sample known. Combining these data with previous SN Ia data sets, we measured H(z) at discrete, uncorrelated epochs, reducing the uncertainty of H(z > 1) from 50% to under 20%, strengthening the evidence for a cosmic jerk—the transition from deceleration in the past to acceleration in the present. The unique leverage of the HST high-redshift SNe Ia provides the first meaningful constraint on the dark energy equation-of-state parameter at z ≥ 1. The result remains consistent with a cosmological constant [w(z) = −1] and rules out rapidly evolving dark energy (dw/dz ≫ 1). The defining property of dark energy, its negative pressure, appears to be present at z > 1, in the epoch preceding acceleration, with ~98% confidence in our primary fit. Moreover, the z > 1 sample-averaged spectral energy distribution is consistent with that of the typical SN Ia over the last 10 Gyr, indicating that any spectral evolution of the properties of SNe Ia with redshift is still below our detection threshold.

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Gamma-ray bursts and the fireball model

1999-06-01

Tsvi Piran

Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the late 1960s. The BATSE detector on the COMPTON-GRO satellite has been detecting one burst per day for the … Gamma-ray bursts (GRBs) have puzzled astronomers since their accidental discovery in the late 1960s. The BATSE detector on the COMPTON-GRO satellite has been detecting one burst per day for the last six years. Its findings have revolutionized our ideas about the nature of these objects. They have shown that GRBs are at cosmological distances. This idea was accepted with difficulties at first. The recent discovery of an X-ray afterglow by the Italian/Dutch satellite BeppoSAX has led to a detection of high red-shift absorption lines in the optical afterglow of GRB970508 and in several other bursts and to the identification of host galaxies to others. This has confirmed the cosmological origin. Cosmological GRBs release ∼1051–1053 erg in a few seconds making them the most (electromagnetically) luminous objects in the Universe. The simplest, most conventional, and practically inevitable, interpretation of these observations is that GRBs result from the conversion of the kinetic energy of ultra-relativistic particles or possibly the electromagnetic energy of a Poynting flux to radiation in an optically thin region. This generic "fireball" model has also been confirmed by the afterglow observations. The "inner engine" that accelerates the relativistic flow is hidden from direct observations. Consequently, it is difficult to infer its structure directly from current observations. Recent studies show, however, that this "inner engine" is responsible for the complicated temporal structure observed in GRBs. This temporal structure and energy considerations indicates that the "inner engine" is associated with the formation of a compact object – most likely a black hole.

Methods and results of an automatic analysis of a complete sample ofSwift-XRT observations of GRBs

2009-07-15

P. A. Evans , A. P. Beardmore , K. L. Page +7 more

We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest … We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2–3, we detail the methods which the Swift-XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift-XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4–6, we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light-curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks.

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A very energetic supernova associated with the γ-ray burst of 29 March 2003

2003-06-18

J. Hjorth , J. Sollerman , P. Møller +7 more

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THEHUBBLE SPACE TELESCOPECLUSTER SUPERNOVA SURVEY. V. IMPROVING THE DARK-ENERGY CONSTRAINTS ABOVEz> 1 AND BUILDING AN EARLY-TYPE-HOSTED SUPERNOVA SAMPLE

2012-01-27

N. Suzuki , D. Rubin , C. Lidman +7 more

We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia … We present Advanced Camera for Surveys, NICMOS, and Keck adaptive-optics-assisted photometry of 20 Type Ia supernovae (SNe Ia) from the Hubble Space Telescope (HST) Cluster Supernova Survey. The SNe Ia were discovered over the redshift interval 0.623 < z < 1.415. Of these SNe Ia, 14 pass our strict selection cuts and are used in combination with the world's sample of SNe Ia to derive the best current constraints on dark energy. Of our new SNe Ia, 10 are beyond redshift z = 1, thereby nearly doubling the statistical weight of HST-discovered SNe Ia beyond this redshift. Our detailed analysis corrects for the recently identified correlation between SN Ia luminosity and host galaxy mass and corrects the NICMOS zero point at the count rates appropriate for very distant SNe Ia. Adding these SNe improves the best combined constraint on dark-energy density, ρDE(z), at redshifts 1.0 < z < 1.6 by 18% (including systematic errors). For a flat ΛCDM universe, we find ΩΛ = 0.729 ± 0.014 (68% confidence level (CL) including systematic errors). For a flat wCDM model, we measure a constant dark-energy equation-of-state parameter w = −1.013+0.068−0.073 (68% CL). Curvature is constrained to ∼0.7% in the owCDM model and to ∼2% in a model in which dark energy is allowed to vary with parameters w0 and wa. Further tightening the constraints on the time evolution of dark energy will require several improvements, including high-quality multi-passband photometry of a sample of several dozen z > 1 SNe Ia. We describe how such a sample could be efficiently obtained by targeting cluster fields with WFC3 on board HST. The updated supernova Union2.1 compilation of 580 SNe is available at http://supernova.lbl.gov/Union.

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The Supernova Legacy Survey: measurement of $\Omega_{\mathsf{M}}$, $\Omega_\mathsf{\Lambda}$ andwfrom the first year data set

2006-01-27

P. Astier , J. Guy , N. Regnault +7 more

We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of the 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color … We present distance measurements to 71 high redshift type Ia supernovae discovered during the first year of the 5-year Supernova Legacy Survey (SNLS). These events were detected and their multi-color light-curves measured using the MegaPrime/MegaCam instrument at the Canada-France-Hawaii Telescope (CFHT), by repeatedly imaging four one-square degree fields in four bands, as part of the CFHT Legacy Survey (CFHTLS). Follow-up spectroscopy was performed at the VLT, Gemini and Keck telescopes to confirm the nature of the supernovae and to measure their redshift. With this data set, we have built a Hubble diagram extending to , with all distance measurements involving at least two bands. Systematic uncertainties are evaluated making use of the multi-band photometry obtained at CFHT. Cosmological fits to this first year SNLS Hubble diagram give the following results: for a flat ΛCDM model; and for a flat cosmology with constant equation of state w when combined with the constraint from the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations.

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Improved Cosmological Constraints from New, Old, and Combined Supernova Data Sets

2008-10-16

M. Kowalski , D. Rubin , G. Aldering +7 more

We present a new compilation of Type Ia supernovae (SNe Ia), a new dataset of low-redshift nearby-Hubble-flow SNe and new analysis procedures to work with these heterogeneous compilations. This ``Union'' … We present a new compilation of Type Ia supernovae (SNe Ia), a new dataset of low-redshift nearby-Hubble-flow SNe and new analysis procedures to work with these heterogeneous compilations. This ``Union'' compilation of 414 SN Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older datasets, as well as the recently extended dataset of distant supernovae observed with HST. A single, consistent and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density is $Ω_Λ= 0.713^{+0.027}_{-0.029} (stat)}^{+0.036}_{-0.039} (sys)}$, for a flat, LCDM Universe. Assuming a constant equation of state parameter, $w$, the combined constraints from SNe, BAO and CMB give $w=-0.969^{+0.059}_{-0.063}(stat)^{+0.063}_{-0.066} (sys)$. While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a $w$ that varies with redshift. In particular, the current SN data do not yet significantly constrain $w$ at $z>1$. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available.

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Type Ia Supernova Discoveries atz> 1 from theHubble Space Telescope: Evidence for Past Deceleration and Constraints on Dark Energy Evolution

2004-05-19

Adam G. Riess , L. Strolger , J. Tonry +7 more

We have discovered 16 Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to provide the first conclusive evidence for cosmic deceleration that preceded … We have discovered 16 Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to provide the first conclusive evidence for cosmic deceleration that preceded the current epoch of cosmic acceleration. These objects, discovered during the course of the GOODS ACS Treasury program, include 6 of the 7 highest redshift SNe Ia known, all at z > 1.25, and populate the Hubble diagram in unexplored territory. The luminosity distances to these objects and to 170 previously reported SNe Ia have been determined using empirical relations between light-curve shape and luminosity. A purely kinematic interpretation of the SN Ia sample provides evidence at the greater than 99% confidence level for a transition from deceleration to acceleration or, similarly, strong evidence for a cosmic jerk. Using a simple model of the expansion history, the transition between the two epochs is constrained to be at z = 0.46 ± 0.13. The data are consistent with the cosmic concordance model of ΩM ≈ 0.3, ΩΛ ≈ 0.7 (χ = 1.06) and are inconsistent with a simple model of evolution or dust as an alternative to dark energy. For a flat universe with a cosmological constant, we measure ΩM = 0.29 ± (equivalently, ΩΛ = 0.71). When combined with external flat-universe constraints, including the cosmic microwave background and large-scale structure, we find w = -1.02 ± (and w < -0.76 at the 95% confidence level) for an assumed static equation of state of dark energy, P = wρc2. Joint constraints on both the recent equation of state of dark energy, w0, and its time evolution, dw/dz, are a factor of ~8 more precise than the first estimates and twice as precise as those without the SNe Ia discovered with HST. Our constraints are consistent with the static nature of and value of w expected for a cosmological constant (i.e., w0 = -1.0, dw/dz = 0) and are inconsistent with very rapid evolution of dark energy. We address consequences of evolving dark energy for the fate of the universe.

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The High‐Z Supernova Search: Measuring Cosmic Deceleration and Global Curvature of the Universe Using Type Ia Supernovae

1998-11-01

B. Schmidt , N. B. Suntzeff , M. M. Phillips +7 more

The High-Z Supernova Search is an international collaboration to discover and monitor Type Ia supernovae (SNe Ia) at z > 0.2 with the aim of measuring cosmic deceleration and global … The High-Z Supernova Search is an international collaboration to discover and monitor Type Ia supernovae (SNe Ia) at z > 0.2 with the aim of measuring cosmic deceleration and global curvature. Our collaboration has pursued a basic understanding of supernovae in the nearby universe, discovering and observing a large sample of objects and developing methods to measure accurate distances with SNe Ia. This paper describes the extension of this program to z ≥ 0.2, outlining our search techniques and follow-up program. We have devised high-throughput filters that provide accurate two-color rest frame B and V light curves of SNe Ia, enabling us to produce precise, extinction-corrected luminosity distances in the range 0.25 < z < 0.55. Sources of systematic error from K-corrections, extinction, selection effects, and evolution are investigated, and their effects estimated. We present photometric and spectral observations of SN 1995K, our program's first supernova (SN), and use the data to obtain a precise measurement of the luminosity distance to the z = 0.479 host galaxy. This object, when combined with a nearby sample of SNe, yields an estimate for the matter density of the universe of ΩM=-0.2−0.8+1.0 if ΩΛ = 0. For a spatially flat universe composed of normal matter and a cosmological constant, we find ΩM=0.4−0.4+0.5, Ω=0.6−0.5+0.4. We demonstrate that with a sample of ~30 objects, we should be able to determine relative luminosity distances over the range 0 < z < 0.5 with sufficient precision to measure ΩM with an uncertainty of ±0.2.

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Cosmological Results from High‐zSupernovae

2003-08-20

J. Tonry , B. Schmidt , B. Barris +7 more

The High-z Supernova Search Team has discovered and observed 8 new supernovae in the redshift interval z=0.3-1.2. These independent observations, confirm the result of Riess et al. (1998a) and Perlmutter … The High-z Supernova Search Team has discovered and observed 8 new supernovae in the redshift interval z=0.3-1.2. These independent observations, confirm the result of Riess et al. (1998a) and Perlmutter et al. (1999) that supernova luminosity distances imply an accelerating universe. More importantly, they extend the redshift range of consistently observed SN Ia to z~1, where the signature of cosmological effects has the opposite sign of some plausible systematic effects. Consequently, these measurements not only provide another quantitative confirmation of the importance of dark energy, but also constitute a powerful qualitative test for the cosmological origin of cosmic acceleration. We find a rate for SN Ia of 1.4+/-0.5E-04 h^3/Mpc^3/yr at a mean redshift of 0.5. We present distances and host extinctions for 230 SN Ia. These place the following constraints on cosmological quantities: if the equation of state parameter of the dark energy is w=-1, then H0 t0 = 0.96+/-0.04, and O_l - 1.4 O_m = 0.35+/-0.14. Including the constraint of a flat Universe, we find O_m = 0.28+/-0.05, independent of any large-scale structure measurements. Adopting a prior based on the 2dF redshift survey constraint on O_m and assuming a flat universe, we find that the equation of state parameter of the dark energy lies in the range -1.48<w<-0.72 at 95% confidence. If we further assume that w>-1, we obtain w<-0.73 at 95% confidence. These constraints are similar in precision and in value to recent results reported using the WMAP satellite, also in combination with the 2dF redshift survey.

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Measurements of the Cosmological Parameters Ω and Λ from the First Seven Supernovae atz≥ 0.35

1997-07-10

S. Perlmutter , S. Gabi , G. Goldhaber +7 more

We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven … We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven of more than 28 supernovae discovered to date in the high-redshift supernova search of the Supernova Cosmology Project. We find an observational dispersion in peak magnitudes of σMB=0.27; this dispersion narrows to σMB, corr=0.19 after "correcting" the magnitudes using the light-curve "width-luminosity" relation found for nearby (z ≤ 0.1) Type Ia supernovae from the Calán/Tololo survey (Hamuy et al.). Comparing light-curve width-corrected magnitudes as a function of redshift of our distant (z = 0.35-0.46) supernovae to those of nearby Type Ia supernovae yields a global measurement of the mass density, ΩM=0.88+ 0.69−0.60 for a Λ = 0 cosmology. For a spatially flat universe (i.e., ΩM + ΩΛ = 1), we find ΩM=0.94+ 0.34−0.28 or, equivalently, a measurement of the cosmological constant, ΩΛ=0.06+ 0.28−0.34 ( < 0.51 at the 95% confidence level). For the more general Friedmann-Lemaître cosmologies with independent ΩM and ΩΛ, the results are presented as a confidence region on the ΩM-ΩΛ plane. This region does not correspond to a unique value of the deceleration parameter q0. We present analyses and checks for statistical and systematic errors and also show that our results do not depend on the specifics of the width-luminosity correction. The results for ΩΛ-versus-ΩM are inconsistent with Λ-dominated, low-density, flat cosmologies that have been proposed to reconcile the ages of globular cluster stars with higher Hubble constant values.

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Binary Interaction Dominates the Evolution of Massive Stars

2012-07-26

H. Sana , S. E. de Mink , A. de Koter +7 more

The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on … The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

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The Great Observatories Origins Deep Survey: Initial Results from Optical and Near-Infrared Imaging

2004-01-09

Mauro Giavalisco , Henry C. Ferguson , Anton M. Koekemoer +7 more

This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on … This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with the Hubble Space Telescope and the Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in the ACS F435W, F606W, F814W, and F850LP bands, divided into two well-studied fields. Existing deep observations from the Chandra X-Ray Observatory and ground-based facilities are supplemented with new, deep imaging in the optical and near-infrared from the European Southern Observatory and from the Kitt Peak National Observatory. Deep observations with the Space Infrared Telescope Facility are scheduled. Reduced data from all facilities are being released worldwide within 3-6 months of acquisition. Together, this data set provides two deep reference fields for studies of distant normal and active galaxies, supernovae, and faint stars in our own Galaxy. This Letter serves to outline the survey strategy and describe the specific data that have been used in the accompanying letters, summarizing the reduction procedures and sensitivity limits.

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THE LARGE AREA TELESCOPE ON THEFERMI GAMMA-RAY SPACE TELESCOPEMISSION

2009-05-08

W. B. Atwood , A. A. Abdo , M. Ackermann +7 more

(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy … (Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. This paper describes the LAT, its pre-flight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4x4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 x,y tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an 8 layer hodoscopic configuration with a total depth of 8.6 radiation lengths. The aspect ratio of the tracker (height/width) is 0.4 allowing a large field-of-view (2.4 sr). Data obtained with the LAT are intended to (i) permit rapid notification of high-energy gamma-ray bursts (GRBs) and transients and facilitate monitoring of variable sources, (ii) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (iii) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (iv) localize point sources to 0.3 - 2 arc minutes, (v) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (vi) measure the diffuse isotropic gamma-ray background up to TeV energies, and (vii) explore the discovery space for dark matter.

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TheSwiftGamma‐Ray Burst Mission

2004-08-20

N. Gehrels , G. Chincarini , P. Giommi +7 more

The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the … The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts yr-1 and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to (1) determine the origin of GRBs, (2) classify GRBs and search for new types, (3) study the interaction of the ultrarelativistic outflows of GRBs with their surrounding medium, and (4) use GRBs to study the early universe out to z > 10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector that will detect bursts, calculate 1'-4' positions, and trigger autonomous spacecraft slews; a narrow-field X-ray telescope that will give 5'' positions and perform spectroscopy in the 0.2-10 keV band; and a narrow-field UV/optical telescope that will operate in the 170-600 nm band and provide 03 positions and optical finding charts. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of ~1 mcrab (~2 × 10-11 ergs cm-2 s-1 in the 15-150 keV band), more than an order of magnitude better than HEAO 1 A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients, with rapid data downlink and uplink available through the NASA TDRSS system. Swift transient data will be rapidly distributed to the astronomical community, and all interested observers are encouraged to participate in follow-up measurements. A Guest Investigator program for the mission will provide funding for community involvement. Innovations from the Swift program applicable to the future include (1) a large-area gamma-ray detector using the new CdZnTe detectors, (2) an autonomous rapid-slewing spacecraft, (3) a multiwavelength payload combining optical, X-ray, and gamma-ray instruments, (4) an observing program coordinated with other ground-based and space-based observatories, and (5) immediate multiwavelength data flow to the community. The mission is currently funded for 2 yr of operations, and the spacecraft will have a lifetime to orbital decay of ~8 yr.

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Discovery of a supernova explosion at half the age of the Universe

1998-01-01

S. Perlmutter , G. Aldering , M. Della Valle +7 more

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The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample

2018-05-29

D. Scolnic , D. O. Jones , A. Rest +7 more

We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the … We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the PS1 SN photometry, astrometry and calibration that reduce the systematic uncertainties in the PS1 SN Ia distances. We combine the subset of 279 PS1 SN Ia ($0.03 < z < 0.68$) with useful distance estimates of SN Ia from SDSS, SNLS, various low-z and HST samples to form the largest combined sample of SN Ia consisting of a total of 1048 SN Ia ranging from $0.01 < z < 2.3$, which we call the `Pantheon Sample'. When combining Planck 2015 CMB measurements with the Pantheon SN sample, we find $\Omega_m=0.307\pm0.012$ and $w = -1.026\pm0.041$ for the wCDM model. When the SN and CMB constraints are combined with constraints from BAO and local H0 measurements, the analysis yields the most precise measurement of dark energy to date: $w0 = -1.007\pm 0.089$ and $wa = -0.222 \pm0.407$ for the w0waCDM model. Tension with a cosmological constant previously seen in an analysis of PS1 and low-z SNe has diminished after an increase of $2\times$ in the statistics of the PS1 sample, improved calibration and photometry, and stricter light-curve quality cuts. We find the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. This must be addressed for future progress in using SN Ia to measure dark energy.

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Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A

2017-10-16

B. P. Abbott , R. Abbott , T. D. Abbott +7 more

On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi … On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anticoincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times 10^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short gamma-ray bursts. We use the observed time delay of $(+1.74 \pm 0.05)\,$s between GRB 170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between $-3\times 10^{-15}$ and $+7\times 10^{-16}$ times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma rays. GRB 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1--1.4 per year during the 2018-2019 observing run and 0.3--1.7 per year at design sensitivity.

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The Swift Ultra-Violet/Optical Telescope

2005-10-01

Peter W. A. Roming , T. Kennedy , K. O. Mason +7 more

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New Constraints on ΩM, ΩΛ, andwfrom an Independent Set of 11 High‐Redshift Supernovae Observed with theHubble Space Telescope

2003-11-20

R. A. Knop , G. Aldering , R. Amanullah +7 more

We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z = 0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This … We report measurements of ΩM, ΩΛ, and w from 11 supernovae (SNe) at z = 0.36-0.86 with high-quality light curves measured using WFPC2 on the Hubble Space Telescope (HST). This is an independent set of high-redshift SNe that confirms previous SN evidence for an accelerating universe. The high-quality light curves available from photometry on WFPC2 make it possible for these 11 SNe alone to provide measurements of the cosmological parameters comparable in statistical weight to the previous results. Combined with earlier Supernova Cosmology Project data, the new SNe yield a measurement of the mass density ΩM = 0.25 (statistical) ± 0.04 (identified systematics), or equivalently, a cosmological constant of ΩΛ = 0.75 (statistical) ± 0.04 (identified systematics), under the assumptions of a flat universe and that the dark energy equation-of-state parameter has a constant value w = -1. When the SN results are combined with independent flat-universe measurements of ΩM from cosmic microwave background and galaxy redshift distortion data, they provide a measurement of w = -1.05 (statistical) ± 0.09 (identified systematic), if w is assumed to be constant in time. In addition to high-precision light-curve measurements, the new data offer greatly improved color measurements of the high-redshift SNe and hence improved host galaxy extinction estimates. These extinction measurements show no anomalous negative E(B-V) at high redshift. The precision of the measurements is such that it is possible to perform a host galaxy extinction correction directly for individual SNe without any assumptions or priors on the parent E(B-V) distribution. Our cosmological fits using full extinction corrections confirm that dark energy is required with P(ΩΛ > 0) > 0.99, a result consistent with previous and current SN analyses that rely on the identification of a low-extinction subset or prior assumptions concerning the intrinsic extinction distribution.

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Discovery of the peculiar supernova 1998bw in the error box of GRB980425

1998-06-12

T. J. Galama , P. M. Vreeswijk , J. van Paradijs +7 more

The discovery of X-ray, optical and radio afterglows of gamma-ray bursts (GRBs) and the measurements of the distances to some of them have established that these events come from Gpc … The discovery of X-ray, optical and radio afterglows of gamma-ray bursts (GRBs) and the measurements of the distances to some of them have established that these events come from Gpc distances and are the most powerful photon emitters known in the Universe, with peak luminosities up to 10^52 erg/s. We here report the discovery of an optical transient, in the BeppoSAX Wide Field Camera error box of GRB980425, which occurred within about a day of the gamma-ray burst. Its optical light curve, spectrum and location in a spiral arm of the galaxy ESO 184-G82, at a redshift z = 0.0085, show that the transient is a very luminous type Ic supernova, SN1998bw. The peculiar nature of SN1998bw is emphasized by its extraordinary radio properties which require that the radio emitter expand at relativistical speed. Since SN1998bw is very different from all previously observed afterglows of GRBs, our discovery raises the possibility that very different mechanisms may give rise to GRBs, which differ little in their gamma-ray properties.

Supernovae of type I as end products of the evolution of binaries with components of moderate initial mass (M not greater than about 9 solar masses)

1984-02-01

Jr. Iben I. , А. В. Тутуков

view Abstract Citations (1575) References (108) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supernovae of type I as end products of the evolution of binaries with components … view Abstract Citations (1575) References (108) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supernovae of type I as end products of the evolution of binaries with components of moderate initial mass. Iben, I., Jr. ; Tutukov, A. V. Abstract Formation frequencies of binary systems which may become Type I supernovae are estimated. Presupernova systems consist of a CO or He degenerate dwarf and a (potential) mass donor (main-sequence star = MS; low-mass red giant = RG; asymptotic giant branch star = AGB; CO or He degenerate dwarf = CODD or HeDD). Mass transfer is driven by nuclear evolution (E), capture from wind (W), a magnetic stellar wind (MSW), or gravitational wave radiation (GWR). For several scenarios, the composition of accretor, nature of donor, driving mechanism, and formation frequency (in 10-3 yr-1 per 1010 L_sun; in the B band), respectively, are the following: (1) CO, RG, E, 10-2- 10-3; (2) CO, AGB, W, 4; (3) CO, MS, MSW, 2; (4) He, MS, MSW, 2; (5) CO or He, near-MS, E+MSW, 3; (6) CO, CODD, GWR, 8; (7) CO, HeDD, GWR, 1; (8) He, HeDD, GWR, 5. The galactic Type I supernova frequency is 10. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1984 DOI: 10.1086/190932 Bibcode: 1984ApJS...54..335I Keywords: Binary Stars; Stellar Evolution; Stellar Mass; Supernovae; Dwarf Stars; Planetary Nebulae; Red Giant Stars; Stellar Cores; Stellar Envelopes; Stellar Mass Accretion; Stellar Winds; X Ray Sources; Astrophysics full text sources ADS | data products SIMBAD (4)

A 2.4% DETERMINATION OF THE LOCAL VALUE OF THE HUBBLE CONSTANT*

2016-07-20

Adam G. Riess , Lucas M. Macri , Samantha Hoffmann +7 more

We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to reduce the uncertainty in the local value of the Hubble constant (H_0) from 3.3% to … We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to reduce the uncertainty in the local value of the Hubble constant (H_0) from 3.3% to 2.4%. Improvements come from new, near-infrared observations of Cepheid variables in 11 new hosts of recent SNe~Ia, more than doubling the sample of SNe~Ia having a Cepheid-calibrated distance for a total of 19; these leverage the magnitude-z relation based on 300 SNe~Ia at z<0.15. All 19 hosts and the megamaser system NGC4258 were observed with WFC3, thus nullifying cross-instrument zeropoint errors. Other improvements include a 33% reduction in the systematic uncertainty in the maser distance to NGC4258, more Cepheids and a more robust distance to the LMC from late-type DEBs, HST observations of Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW) Cepheids. We consider four geometric distance calibrations of Cepheids: (i) megamasers in NGC4258, (ii) 8 DEBs in the LMC, (iii) 15 MW Cepheids with parallaxes, and (iv) 2 DEBs in M31. H_0 from each is 72.25+/-2.51, 72.04+/-2.67, 76.18+/-2.37, and 74.50+/-3.27 km/sec/Mpc, respectively. Our best estimate of 73.24+/-1.74 km/sec/Mpc combines the anchors NGC4258, MW, and LMC, and includes systematic errors for a final uncertainty of 2.4%. This value is 3.4 sigma higher than 66.93+/-0.62 km/sec/Mpc predicted by LambdaCDM with 3 neutrinos with mass 0.06 eV and the Planck data, but reduces to 2.1 sigma relative to the prediction of 69.3+/-0.7 km/sec/Mpc with the combination of WMAP+ACT+SPT+BAO, suggesting systematic uncertainties in CMB measurements may play a role in the tension. If we take the conflict between Planck and H_0 at face value, one plausible explanation could involve an additional source of dark radiation in the early Universe in the range of Delta N_eff=0.4-1. We anticipate significant improvements in H_0 from upcoming parallax measurements.

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LSST: From Science Drivers to Reference Design and Anticipated Data Products

2019-03-10

Željko Ivezić , S. M. Kahn , J. A. Tyson +7 more

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single … (Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.

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Spectra and Light Curves of Gamma-Ray Burst Afterglows

1998-04-10

Re’em Sari , Tsvi Piran , Ramesh Narayan

The recently discovered gamma-ray burst afterglow is believed to be described reasonably well by synchrotron emission from a decelerating relativistic shell that collides with an external medium. To compare theoretical … The recently discovered gamma-ray burst afterglow is believed to be described reasonably well by synchrotron emission from a decelerating relativistic shell that collides with an external medium. To compare theoretical models with afterglow observations, we calculate here the broadband spectrum and corresponding light curve of synchrotron radiation from a power-law distribution of electrons in an expanding relativistic shock. Both the spectrum and the light curve consist of several power-law segments with related indices. The light curve is constructed under two limiting models for the hydrodynamic evolution of the shock: fully adiabatic and fully radiative. We give explicit relations between the spectral index and the temporal power-law index. Future observations should be able to distinguish between the possible behaviors and determine the type of solution.

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THE MAN BEHIND THE CURTAIN: X-RAYS DRIVE THE UV THROUGH NIR VARIABILITY IN THE 2013 ACTIVE GALACTIC NUCLEUS OUTBURST IN NGC 2617

2014-05-21

B. J. Shappee , J. L. Prieto , D. Grupe +7 more

After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from … After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered a significant brightening of the inner region of NGC 2617, we began a ~70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look Active Galactic Nuclei (AGN)" are rare and provide us with important insights about AGN physics. Based on the Hbeta line width and the radius-luminosity relation, we estimate the mass of central black hole to be (4 +/- 1) x 10^7 M_sun. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a black hole of the estimated mass that is illuminated by the observed, variable X-ray fluxes.

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Discovery of a Supernova Explosion at Half the Age of the Universe and its Cosmological Implications

1997-12-16

S. Perlmutter , G. Aldering , M. Della Valle +7 more

The ultimate fate of the universe, infinite expansion or a big crunch, can be determined by measuring the redshifts, apparent brightnesses, and intrinsic luminosities of very distant supernovae. Recent developments … The ultimate fate of the universe, infinite expansion or a big crunch, can be determined by measuring the redshifts, apparent brightnesses, and intrinsic luminosities of very distant supernovae. Recent developments have provided tools that make such a program practicable: (1) Studies of relatively nearby Type Ia supernovae (SNe Ia) have shown that their intrinsic luminosities can be accurately determined; (2) New research techniques have made it possible to schedule the discovery and follow-up observations of distant supernovae, producing well over 50 very distant (z = 0.3 -- 0.7) SNe Ia to date. These distant supernovae provide a record of changes in the expansion rate over the past several billion years. By making precise measurements of supernovae at still greater distances, and thus extending this expansion history back far enough in time, we can distinguish the slowing caused by the gravitational attraction of the universe's mass density Omega_M from the effect of a possibly inflationary pressure caused by a cosmological constant Lambda. We report here the first such measurements, with our discovery of a Type Ia supernova (SN 1997ap) at z = 0.83. Measurements at the Keck II 10-m telescope make this the most distant spectroscopically confirmed supernova. Over two months of photometry of SN 1997ap with the Hubble Space Telescope and ground-based telescopes, when combined with previous measurements of nearer SNe Ia, suggests that we may live in a low mass-density universe. Further supernovae at comparable distances are currently scheduled for ground and space-based observations.

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A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km s−1 Mpc−1 Uncertainty from the Hubble Space Telescope and the SH0ES Team

2022-07-01

Adam G. Riess , Wenlong Yuan , Lucas M. Macri +7 more

We report observations from HST of Cepheids in the hosts of 42 SNe Ia used to calibrate the Hubble constant (H0). These include all suitable SNe Ia in the last … We report observations from HST of Cepheids in the hosts of 42 SNe Ia used to calibrate the Hubble constant (H0). These include all suitable SNe Ia in the last 40 years at z<0.01, measured with >1000 orbits, more than doubling the sample whose size limits the precision of H0. The Cepheids are calibrated geometrically from Gaia EDR3 parallaxes, masers in N4258 (here tripling that Cepheid sample), and DEBs in the LMC. The Cepheids were measured with the same WFC3 instrument and filters (F555W, F814W, F160W) to negate zeropoint errors. We present multiple verifications of Cepheid photometry and tests of background determinations that show measurements are accurate in the presence of crowding. The SNe calibrate the mag-z relation from the new Pantheon+ compilation, accounting here for covariance between all SN data, with host properties and SN surveys matched to negate differences. We decrease the uncertainty in H0 to 1 km/s/Mpc with systematics. We present a comprehensive set of ~70 analysis variants to explore the sensitivity of H0 to selections of anchors, SN surveys, z range, variations in the analysis of dust, metallicity, form of the P-L relation, SN color, flows, sample bifurcations, and simultaneous measurement of H(z). Our baseline result from the Cepheid-SN sample is H0=73.04+-1.04 km/s/Mpc, which includes systematics and lies near the median of all analysis variants. We demonstrate consistency with measures from HST of the TRGB between SN hosts and NGC 4258 with Cepheids and together these yield 72.53+-0.99. Including high-z SN Ia we find H0=73.30+-1.04 with q0=-0.51+-0.024. We find a 5-sigma difference with H0 predicted by Planck+LCDM, with no indication this arises from measurement errors or analysis variations considered to date. The source of this now long-standing discrepancy between direct and cosmological routes to determining the Hubble constant remains unknown.

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The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package*

2022-08-01

The Astropy Collaboration , Adrian M. Price-Whelan , Pey Lian Lim +7 more

Abstract The Astropy Project supports and fosters the development of open-source and openly developed Python packages that provide commonly needed functionality to the astronomical community. A key element of the … Abstract The Astropy Project supports and fosters the development of open-source and openly developed Python packages that provide commonly needed functionality to the astronomical community. A key element of the Astropy Project is the core package astropy , which serves as the foundation for more specialized projects and packages. In this article, we summarize key features in the core package as of the recent major release, version 5.0, and provide major updates on the Project. We then discuss supporting a broader ecosystem of interoperable packages, including connections with several astronomical observatories and missions. We also revisit the future outlook of the Astropy Project and the current status of Learn Astropy. We conclude by raising and discussing the current and future challenges facing the Project.

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Multi-messenger Observations of a Binary Neutron Star Merger

2020-11-23

B. P. Abbott , R. Abbott , T. D. Abbott +7 more

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo … On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged)

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Tracing High-z Galaxies in X-Rays with JWST and Chandra

2025-06-25

Aidan Kaminsky , N. Cappelluti , G. Hasinger +7 more | The Astrophysical Journal

Abstract We leverage James Webb Space Telescope (JWST) data from the COSMOS-Web survey in order to provide updated measurements on the auto-power spectrum of the now resolved cosmic near-infrared background … Abstract We leverage James Webb Space Telescope (JWST) data from the COSMOS-Web survey in order to provide updated measurements on the auto-power spectrum of the now resolved cosmic near-infrared background (CIB) and its coherence with the unresolved soft cosmic X-ray background (CXB) observed by Chandra at z > 6. Maps of the CIB in the F277W and F444W NIRCam filters are constructed with sources fainter than m AB = 25 and cross-correlated with the CXB in the [0.5–2] keV band. We find that on scales between 1″ and 1000″ the CIB–CXB cross-power in both NIRCam filters is statistically significant, with signal-to-noise ratios (S/Ns) of 4.80 and 6.20, respectively, from redshifts 0 ≤ z ≤ 13. In our high- z (6 ≤ z ≤ 13) interval we find coherence in both filters, with S/Ns of 7.32 and 5.39, respectively. These results suggest that there are X-ray-emitting galaxies resolved by JWST, including star-forming galaxies and active galactic nuclei. We fit the large-scale biasing of the IR sources producing the CIB as a function of z with results consistent with prior measurements, and place constraints on the CXB flux and biasing at low and high z . The CXB flux measurements presented in this study suggest that approximately 94% of the [0.5–2] keV CXB is resolved, and this value is consistent within 2 σ with the complete resolution of the [0.5–2] keV CXB.

ASKAP–EMU radio continuum detection of planetary nebula NGC 5189: the “Infinity” nebula

2025-06-24

A. D. Asher , Z. J. Smeaton , M. D. Filipović +4 more | Publications of the Astronomical Society of Australia

Abstract We report the radio continuum detection of well known Galactic Planetary Nebula (PN) NGC5189, observed at 943MHz during the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the … Abstract We report the radio continuum detection of well known Galactic Planetary Nebula (PN) NGC5189, observed at 943MHz during the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. Two detections of NGC5189 have been made during the survey, of better resolution than previous radio surveys. Both measurements of the integrated flux density are consistent with each other, at S 943 MHz = 0.33 ± 0.03 Jy, and the spectral luminosity is L 943 MHz = 8.89 × 10 13 W m –2 Hz –1 . Using available flux density measurements for radio-detections of NGC5189, we calculate a radio surface brightness at 1GHz and measure Σ 1 GHz = 6.0 × 10 –21 W m –2 Hz –1 sr –1 , which is in the expected range for Galactic PNe. We measure an apparent size of 3.′4×2.′2 corresponding to physical diameters of 1.48 pc × 0.96 pc, and combine available radio observations of NGC5189 to estimate a spectral index of α = 0.12 ± 0.05. Hence, we agree with previous findings that NGC5189 is a thermal (free–free) emitting nebula. Additional measurements of the optical depth (τ = 0.00246) and electron density ( N e = 138 cm –3 ) support our findings that NGC5189 is optically thin at 943 MHz. Furthermore, the radio contours from the ASKAP–EMU image have been overlaid onto a Hubble Space Telescope (HST) Wide Field Camera 3 image, demonstrating that the radio morphology closely traces the optical. Notably, the contour alignment for the innermost region highlights the two envelopes of gas previously reported to be low-ionisation structures, which is considered a defining feature of post common–envelope PNe that surround a central Wolf-Rayet star.

Blinkverse 2.0: Updated Host Galaxies for Fast Radio Bursts

2025-06-24

Jiaying Xu , Chao‐Wei Tsai , Sean E. Lake +7 more | Universe

Studying the host galaxies of fast radio bursts (FRBs) is critical to understanding the formation processes of their sources and, hence, the mechanisms by which they radiate. Toward this end, … Studying the host galaxies of fast radio bursts (FRBs) is critical to understanding the formation processes of their sources and, hence, the mechanisms by which they radiate. Toward this end, we have extended the Blinkverse database version 1.0, which already included burst information about FRBs observed by various telescopes, by adding information about 92 published FRB host galaxies to make version 2.0. Each FRB host has 18 parameters describing it, including redshift, stellar mass, star-formation rate, emission line fluxes, etc. In particular, each FRB host includes images collated by FASTView, streamlining the process of looking for clues to understanding the origin of FRBs. FASTView is a tool and API for quickly exploring astronomical sources using archival imaging, photometric, and spectral data. This effort represents the first step in building Blinkverse into a comprehensive tool for facilitating source observation and analysis.

Redshift tomography of the kinematic matter dipole

2025-06-24

Sebastian von Hausegger , Charles Dalang | Physical review. D/Physical review. D.

The dipole anisotropy induced by our peculiar motion in the sky distribution of cosmologically distant sources is an important consistency test of the standard Friedmann-Lemaître-Robertson-Walker cosmology. In this work, we … The dipole anisotropy induced by our peculiar motion in the sky distribution of cosmologically distant sources is an important consistency test of the standard Friedmann-Lemaître-Robertson-Walker cosmology. In this work, we formalize how to compute the kinematic matter dipole in redshift bins. Apart from the usual terms arising from angular aberration and flux boosting, there is a contribution from the boosting of the redshifts that becomes important when considering a sample selected on observed redshift, leading to nonvanishing correction terms. We discuss examples and provide expressions to incorporate arbitrary redshift selection functions. We also discuss the effect of redshift measurement uncertainties in this context, in particular in upcoming surveys for which we provide estimates of the correction terms. Depending on the shape of a sample’s redshift distribution and on the applied redshift cuts, the correction terms can become substantial, even to the degree that the direction of the dipole is reversed. Lastly, we discuss how cuts on variables correlated with observed redshift, such as color, can induce additional correction terms. Published by the American Physical Society 2025

“Oh FUors, Where Art Thou?”: A Search for Long-lasting Young Stellar Object Outbursts Hiding in Infrared Surveys

2025-06-24

Carlos Contreras Peña , Jeong‐Eun Lee , Ho-Gyu Lee +7 more | The Astrophysical Journal

Abstract Long-lasting episodes of high accretion can strongly impact stellar and planetary formation. However, the universality of these events during the formation of young stellar objects (YSOs) is still under … Abstract Long-lasting episodes of high accretion can strongly impact stellar and planetary formation. However, the universality of these events during the formation of young stellar objects (YSOs) is still under debate. Accurate statistics of strong outbursts (FUors) are necessary to understand the role of episodic accretion bursts. In this work, we search for a population of FUors that may have gone undetected in the past because they either (a) went into outburst before the start of modern monitoring surveys and are now slowly fading back into quiescence or (b) are slow-rising outbursts that would not commonly be classified as candidate FUors. We hypothesize that the light curves of these outbursts should be well fitted by linear models with negative (declining) or positive (rising) slopes. The analysis of the infrared light curves and photometry of ∼99,000 YSO candidates from SPICY yields 717 candidate FUors. Infrared spectroscopy of 20 candidates, from both the literature and obtained by our group, confirms that 18 YSOs are going through long-term outbursts and identifies two evolved sources as contaminants. The number of candidate FUors combined with previously measured values of the frequency of FUor outbursts yields average outburst decay times that are 2.5 times longer than the rise times. In addition, a population of outbursts with rise timescales between 2000 and 5000 days must exist to obtain our observed number of YSOs with positive slopes. Finally, we estimate a mean-burst lifetime of between 45 and 100 yr.

Unveiling the Diversity of Type IIn Supernovae via Systematic Light-curve Modeling

2025-06-23

C. L. Ransome , V. Ashley Villar | The Astrophysical Journal

Abstract Type IIn supernovae (SNe IIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here, we systematically model … Abstract Type IIn supernovae (SNe IIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here, we systematically model the light curves of 142 archival SNe IIn using the Modular Open Source Fitter for Transients. We find that the observed and inferred properties of SN IIn are diverse, but there are some trends. The typical supernova CSM is dense (∼10 −12 g cm −3 ) with highly diverse CSM geometry, with a median CSM mass of ∼1 M ⊙ . The ejecta are typically massive (≳10 M ⊙ ), suggesting massive progenitor systems. We find positive correlations between the CSM mass and the rise and fall times of SNe IIn. Furthermore, there are positive correlations between the rise time and fall times and the r -band luminosity. We estimate the mass-loss rates of our sample (where spectroscopy is available) and find a high median mass-loss rate of ∼10 −2 M ⊙ yr −1 , with a range between 10 −3 and 1 M ⊙ yr −1 . These mass-loss rates are most similar to the mass loss from great eruptions of luminous blue variables, consistent with the direct progenitor detections in the literature. We also discuss the role that binary interactions may play, concluding that at least some of our SNe IIn may be from massive binary systems. Finally, we estimate a detection rate of 1.6 × 10 5 yr −1 in the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory.

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Constraining population III stellar demographics with next-generation gravitational-wave observatories

2025-06-23

NULL AUTHOR_ID | Physical review. D/Physical review. D.

Fresh look at the diffuse ALP background from supernovae

2025-06-23

NULL AUTHOR_ID | Physical review. D/Physical review. D.

News and views (5&6)

2025-06-23

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The Initial Evolution of SN 1993J: Piston Phase versus Standard Model

2025-06-23

C.-I. Björnsson | The Astrophysical Journal

Abstract The evolution of SN 1993J is unlikely to be self-similar. Spatially resolved very long baseline interferometry observations show that the velocity of the outer rim of the radio emission … Abstract The evolution of SN 1993J is unlikely to be self-similar. Spatially resolved very long baseline interferometry observations show that the velocity of the outer rim of the radio emission region breaks at a few hundred days. The reason for this break remains largely unknown. It is argued here that it is due to the transition between an initial piston phase to a later phase, which is described by the standard model. The properties of the reverse shock are quite different for a piston phase as compared to the standard self-similar model. This affects the expected X-ray emission; for example, the reverse shock becomes transparent to X-ray emission much earlier in the piston phase. Furthermore, it is shown that the observed box-like emission line profiles of H α and other optical lines are consistent with an origin from the transition region between the envelope and the core. It is also pointed out that identifying the observed, simultaneous breaks at ≈3100 days in the radio and X-ray light curves with the reverse shock reaching the core makes it possible to directly relate the mass-loss rate of the progenitor star to observables.

SMARTies: a software suite for flexible and fully automated control of multi-sensor telescope stations

2025-06-21

Christoph Bergmann , Johannes Herzog , Benjamin Hofmann +5 more | CEAS Space Journal

Abstract We describe the SMARTnet Instrument Enhancing Software (SMARTies) package, which we developed from scratch for fully automated remote control of our telescope stations within the Small Aperture Robotic Telescope … Abstract We describe the SMARTnet Instrument Enhancing Software (SMARTies) package, which we developed from scratch for fully automated remote control of our telescope stations within the Small Aperture Robotic Telescope Network (SMARTnet). Since March 2024, we have been using SMARTies continually to operate our SMARTnet telescope station in Chile successfully. We include a detailed description of the system design and architecture including the SMARTies modules, which are written in pure and are kept rather abstract, as well as the bespoke device controllers, which facilitate the communication with the actual hardware devices used. SMARTies was designed to fulfil a number of different use cases, including satellite or space debris tracking, survey observations, and observations of astronomical objects, including light curve acquisitions, and is therefore useful for the Space Situational Awareness community and other observational astronomers alike. While a fully automated observing mode following a user-defined schedule was one of the driving factors in the development of SMARTies, it does allow for near real-time manipulations of the schedule and even completely manual operations of the telescope. Because of its object-oriented and modular approach, new SMARTies functionalities can easily be added and different hardware devices can easily be included by adding new device controllers. Therefore, we envision SMARTies to be an extremely useful asset for many telescope operators across the world.

Insight-HXMT Observations of the Extremely Bright GRB 221009A

2025-06-20

Wenlong Zhang , W. C. Xue , Cheng-Kui Li +7 more | The Astrophysical Journal

Abstract The Insight Hard X-ray Modulation Telescope (Insight-HXMT) detected GRB 221009A, the brightest gamma-ray burst (GRB) observed to date, with all its three telescopes, i.e., the High Energy (HE) telescope … Abstract The Insight Hard X-ray Modulation Telescope (Insight-HXMT) detected GRB 221009A, the brightest gamma-ray burst (GRB) observed to date, with all its three telescopes, i.e., the High Energy (HE) telescope (20–250 keV), Medium Energy (ME) telescope (5–30 keV), and Low Energy (LE) telescope (1–10 keV). Here we present the detailed observation results of all three telescopes of Insight-HXMT on the prompt emission of GRB 221009A. After dead-time and data saturation correction, we recovered the light curves of the HE, ME, and LE telescopes and find that they generally track the low-gain light curves of the third member of the Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor (GECAM-C) that are free of data saturation issues. Particularly, the ME light curve matches the GECAM-C light curve in low gain mode above 400 keV, while the LE light curve is more consistent with the GECAM-C above 1.5 MeV. Based on simulation, we find that the signals recorded by ME and LE are actually caused by the secondary particles produced by the interaction between GRB gamma-ray photons and the material of the satellite. Interestingly, the consistency between the ME and LE light curves and GECAM-C demonstrates that ME and LE data could be used to characterize the GRB properties. Especially, the high-time-resolution light curve of ME allowed us, for the first time, to calculate the minimum variability timescale (0.10 s) of the main burst episode of GRB 221009A.

Artificial intelligence pioneers the double-strangeness factory

2025-06-20

Yan He , Takehiko Saito , H. Ekawa +7 more | Research Square (Research Square)

<title>Abstract</title> Artificial intelligence (AI) is transforming not only our daily experiences but also the technological development landscape and scientific research. In this study, we pioneered the application of AI in … <title>Abstract</title> Artificial intelligence (AI) is transforming not only our daily experiences but also the technological development landscape and scientific research. In this study, we pioneered the application of AI in double-strangeness hypernuclear studies. These studies—which investigate quantum systems with strangeness via hyperon interactions—provide insights into fundamental baryon-baryon interactions and contribute to our understanding of the nuclear force and composition of neutron star cores. Specifically, we report the observation of a double-Λ hypernucleus in nuclear emulsion achieved via innovative integration of machine learning techniques. The proposed methodology leverages generative AI and Monte Carlo simulations to produce training datasets combined with object detection AI for effective event identification. Based on the kinematic analysis and charge identification, the observed event was uniquely identified as the production and decay of 13ΛΛB, resulting from Ξ− capture by 14N in the nuclear emulsion. Assuming Ξ− capture in the atomic 3D state, the binding energy of the two Λ hyperons in 13ΛΛB, BΛΛ, was determined as 25.57 ± 1.18(stat.) ± 0.07(syst.) MeV. The ΛΛ interaction energy ∆BΛΛ obtained was 2.83 ± 1.18(stat.) ± 0.14(syst.) MeV. This study marks a new era in double-strangeness research.

Red Supergiant Mass Loss and Mass-Loss Rates

2025-06-20

J. Th. van Loon | Galaxies

This review discusses the causes, nature, importance and observational evidence of mass loss by red supergiants. It arrives at the perception that mass loss finds its origin in the gravity … This review discusses the causes, nature, importance and observational evidence of mass loss by red supergiants. It arrives at the perception that mass loss finds its origin in the gravity which makes the star a star in the first place, and is a mechanism for the star to equilibrate. This is corroborated by a careful examination of various popular historical and recent empirical mass-loss rate prescriptions and theoretical works, and which provides no evidence for an explicit dependence of red supergiant mass loss on metallicity though dust-associated mass loss becomes less prevalent at lower metallicity. It also identifies a common problem in methods that use tracers of mass loss, which do not correct for varying scaling factors (often because there is no information available on which to base such correction) and as a result tend to underestimate mass-loss rates at the lower end. Conversely, dense, extended chromospheres in themselves do not translate into high mass-loss rates, and the significance of stochastic mass loss can be overstated. On a population scale, on the other hand, binary interaction acts as a stochastic agent of mass loss of great import. In all, evidence is overwhelming that points at red supergiants at the lower mass end losing mass at insufficient rates to shed their mantles before core collapse, but massive (at birth) red supergiants to be prone to intense, dusty mass loss which sees them become hotter stars before meeting their fate. This is consistent with the identified progenitors of hydrogen-rich supernovae. Supernova evolution holds great promise to probe the mass loss but we caution against confusing atmospheres with winds. Finally, promising avenues are looked into, which could forge step-change progress in what has been a long and arduous search for the holy grail of red supergiant mass loss. We may yet find it!

Erratum: “A Maximum Likelihood Calibration of the Tip of the Red Giant Branch Luminosity from High Latitude Field Giants Using Gaia Early Data Release 3 Parallaxes” (2022, ApJ, 939, 96)

2025-06-20

Siyang Li , Stefano Casertano , Adam G. Riess | The Astrophysical Journal

Observational diversity of bright long-lived Type II supernovae

2025-06-20

T. Nagao , Tim Reynolds , H. Kuncarayakti +7 more | Astronomy and Astrophysics

In various types of supernovae (SNe), strong interaction between the SN ejecta and circumstellar material (CSM) has been reported. This raises questions about their progenitors and mass-loss processes shortly before … In various types of supernovae (SNe), strong interaction between the SN ejecta and circumstellar material (CSM) has been reported. This raises questions about their progenitors and mass-loss processes shortly before the explosion. Recently, the bright long-lived Type II SN 2021irp was proposed to be a standard Type II SN interacting with disk-like CSM. The observational properties suggest that the progenitor was a massive star (∼8-18 M_⊙) in a binary system and underwent a mass-ejection process due to the binary interaction just before the explosion. Similar scenarios, i.e., a Type II SN interacting with a CSM disk, have also been invoked to explain some Type IIn SNe. Here, we study the diversity of the observational properties of bright long-lived Type II (21irp-like) SNe. We analyze the diversity of their CSM properties, in order to understand their progenitors and mass-loss mechanisms and their relations with the other types of interacting SNe. We performed photometry, spectroscopy, and/or polarimetry for four 21irp-like SNe. Based on these observations as well as published data of SN 2021irp itself and well-observed bright and long-lived type II SNe including SNe 2010jl, 2015da, and 2017hcc, we discuss their CSM characteristics. This sample of SNe shows luminous and long-lived photometric evolution, with some variations in the photometric evolution (from ∼-17 to ∼-20 absolute mag in the r/o band even at ∼ 200 days after the explosion). They show photospheric spectra characterized mainly by Balmer lines for several hundreds of days, with some variations in the shapes of the lines. They show high polarization with slight variations in the polarization degrees (∼1-3 % at the brightness peak) with rapid declines with time (from ∼3-6 % before the peak to ∼1 % at ∼200 days after the peak). The general observational properties are consistent with the disk-CSM-interaction scenario, i.e., typical Type II SNe interacting with disk-like CSM. At the same time, the variation in the observational properties suggest diversity in the CSM mass and the opening angle of the CSM disk. These variations in the CSM properties are likely to be be related to the binary parameters of the progenitor systems and/or the properties of the progenitor and companion stars.

Limits to Star Formation in Post Starburst Galaxies from Type II Supernovae

2025-06-19

Laetile Makoko , Roberto De Propris | Research Notes of the AAS

Abstract We establish significant upper limits to the current star formation rate in two samples of post starburst galaxies by measuring the rate of Type II supernovae from the Zwicky … Abstract We establish significant upper limits to the current star formation rate in two samples of post starburst galaxies by measuring the rate of Type II supernovae from the Zwicky Transient Factory Bright Transient Survey. No Type II supernovae are observed within the Petrosian radii of z < 0.05 post starburst galaxies during this supernova search survey. We calculate that at 95% confidence level the star formation rate in these galaxies is <0.8 M ⊙ yr −1 .

Radio bursts reveal universe’s ‘missing matter’

2025-06-19

Daniel Clery | Science

Mystery signals used to locate gases in the spaces between galaxies. Mystery signals used to locate gases in the spaces between galaxies.

Estimating Global Ejecta Mass Ratios in Tycho’s Supernova Remnant

2025-06-19

Tyler Holland-Ashford , Patrick Slane , Brian J. Williams | The Astrophysical Journal

Abstract In this work, as a follow-up to our similar analysis of Kepler’s supernova remnant (SNR), we estimate total mass ratios of various ejecta elements in Tycho’s SNR using Suzaku … Abstract In this work, as a follow-up to our similar analysis of Kepler’s supernova remnant (SNR), we estimate total mass ratios of various ejecta elements in Tycho’s SNR using Suzaku X-ray data. In our spectral analysis, we account for uncertainties arising from Suzaku’s effective area calibration (5%–15%) and from the unknown filling factors of the various plasma components in our spectral model (1%–10%). We compare our calculated ejecta mass ratios to results from previous X-ray analyses of Tycho’s SNR and to the nucleosynthesis results from Type Ia supernova simulations. Our estimated ejecta mass ratios for Tycho’s SNR are only consistent with simulations that use a ∼90% attenuated 12 C+ 16 O reaction rate (as for Kepler’s SNR), are inconsistent with simulations involving a double detonation of a thick helium layer, and support a Type Ia explosion of normal luminosity where ∼85% of the ejecta has been heated by the reverse shock.

Generation of Large-scale Magnetic Fields Upstream of Gamma-Ray Burst Afterglow Shocks

2025-06-19

Ryan Golant , Arno Vanthieghem , Daniel Grošelj +1 more | The Astrophysical Journal

Abstract The origins of the magnetic fields that power gamma-ray burst (GRB) afterglow emission are not fully understood. One possible channel for generating these fields involves the pre-conditioning of the … Abstract The origins of the magnetic fields that power gamma-ray burst (GRB) afterglow emission are not fully understood. One possible channel for generating these fields involves the pre-conditioning of the circumburst medium: in the early afterglow phase, prompt photons streaming ahead of the GRB external shock can pair produce, seeding the upstream with drifting electron–positron pairs and triggering electromagnetic microinstabilities. To study this process, we employ 2D periodic particle-in-cell simulations in which a cold electron–proton plasma is gradually enriched with warm electron–positron pairs injected at mildly relativistic speeds. We find that continuous pair injection drives the growth of large-scale magnetic fields via filamentation-like instabilities; the temporal evolution of the field is self-similar and depends on a single parameter, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mfenced close="]" open="["> <mml:mrow> <mml:mi>α</mml:mi> <mml:mo>/</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">f</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">pi</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mi>t</mml:mi> <mml:msub> <mml:mrow> <mml:mi>ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">pi</mml:mi> </mml:mrow> </mml:msub> </mml:math> , where α is the ratio of final pair beam density to background plasma density, t f is the duration of pair injection, and ω pi is the plasma frequency of background protons. Extrapolating our results to parameter regimes realistic for long GRBs, we find that upstream pair enrichment generates weak magnetic fields on scales much larger than the proton skin depth; for bright bursts, the extrapolated coherence scale at a shock radius of R ∼ 10 17 cm is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close="〉" open="〈"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>y</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:mfenced> <mml:mspace width="0.25em"/> <mml:mo>∼</mml:mo> <mml:mn>100</mml:mn> <mml:mspace width="0.33em"/> <mml:mi>c</mml:mi> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">pi</mml:mi> </mml:mrow> </mml:msub> </mml:math> , and the corresponding magnetization is σ ∼ 10 −8 for typical circumburst parameters. These results may help explain the persistence of magnetic fields at large distances behind GRB shocks.

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Jet precession in gamma-ray bursts: The roles of fallback accretion and disk dynamics

2025-06-18

Yun-Peng Li , Da-Bin Lin , Guo-Yu Li +1 more | Astronomy and Astrophysics

The precession phenomenon of the jet in a gamma-ray burst (GRB) is a key probe of the physics of the central engine. Previous studies generally assumed a fixed precession period … The precession phenomenon of the jet in a gamma-ray burst (GRB) is a key probe of the physics of the central engine. Previous studies generally assumed a fixed precession period when analysing the temporal profiles in GRBs; however, the dynamic evolution of the fallback process and accretion disk can significantly affect the precession behaviour. In this work we present a jet precession model that incorporates the co-evolution of fallback accretion and the central black hole (BH). Our model demonstrates that the jet precession period initially decreases rapidly during the early fallback phase and subsequently increases nearly linearly as the disk evolves. We find that a higher accretion disk viscosity and a slower BH spin lead to longer precession periods and faster precession period growth rates, and that the geometric structure of the precession system modulates the pulse amplitude of the light curve. By fitting the model to observational data of GRBs with multi-pulse structures, we show that jet precession can naturally explain the increasing pulse intervals and broadened pulse widths observed in both long and short GRBs.

Spectropolarimetry of a Nuclear Transient AT2023clx: Revealing the Geometrical Alignment between the Transient Outflow and the Nuclear Dusty Region

2025-06-18

Kohki Uno , Keiichi Maeda , T. Nagao +7 more | The Astrophysical Journal Letters

Abstract AT2023clx, which occurred in NGC 3799 with a low-ionization nuclear emission-line region (LINER), is one of the most nearby nuclear transients classified as a tidal disruption event (TDE). We … Abstract AT2023clx, which occurred in NGC 3799 with a low-ionization nuclear emission-line region (LINER), is one of the most nearby nuclear transients classified as a tidal disruption event (TDE). We present three-epoch spectropolarimetric follow-up observations of AT2023clx. We detected two polarization components; one is a constant polarization of ∼1% originating from an aspherical outflow associated with the transient, while the other is a blue-excess polarization toward ∼2% originating from a nuclear dusty environment via light echoes. The polarization angle flipped by 90° between the two epochs, indicating that the outflow direction was perpendicular to the dust plane. Furthermore, the polarized flux might suggest that the nuclear dust favors relatively large grains, potentially offering constraints on its physical properties. Such polarization features—the blue excess and the 90° flip—have never been observed in previous TDE polarization samples, highlighting unique mechanisms behind AT2023clx. We propose possible scenarios: the disruption of a star formed within or captured by a nuclear dusty cloud. Given the LINER nature of NGC3799, the dusty region may possibly be linked to a torus or disk associated with a weak active galactic nucleus (AGN). Furthermore, as a more speculative scenario, the event might have been triggered by AGN-like activity, potentially linked to changing-look AGNs or ambiguous nuclear transients. These findings highlight the power of time-series spectropolarimetry of TDEs, not only in probing the origins of nuclear transients but also in investigating the physical properties of nuclear dust.

Measurements of the Diffuse Interstellar Bands at 5780, 5797, and 6614 Å in the Hot Stellar Spectra of the LAMOST LRS DR10

2025-06-17

Xiao-Xiao Ma , A-Li Luo , J. S. Chen +2 more | Research in Astronomy and Astrophysics

Abstract Diffuse Interstellar Bands (DIBs) are crucial tracers of the interstellar medium (ISM), yet their carriers remain poorly understood. While large-scale surveys have advanced DIB studies in cool stellar spectra, … Abstract Diffuse Interstellar Bands (DIBs) are crucial tracers of the interstellar medium (ISM), yet their carriers remain poorly understood. While large-scale surveys have advanced DIB studies in cool stellar spectra, measurements in hot stellar spectra are still limited. Using 287,277 high signal-to-noise (S/N > 50) hot stellar spectra from the tenth data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope low-resolution spectroscopic survey (LAMOST LRS DR10), we systematically measured the three prominent optical DIBs at 5780, 5797, and 6614 Å. We published three catalogs containing 285,103, 279,195, and 281,146 valid measurements for the DIBs at 5780, 5797, and 6614 Å, respectively. Among them, 112,479, 25,232, and 71,048 are high-quality samples after rigorous quality control. To our knowledge, these are the largest hot-star DIB datasets in the northern sky. The catalogs provide spectral metadata, added astrometeric information, DIB profiles, and quality metrics. Our methodology and open-source pipeline ensure reproducibility, while the scale and precision of the data support future statistical studies. We anticipate that these catalogs will highlight the LAMOST's role in advancing DIB research and deepening our understanding of the ISM.

Explaining Nonmerger Gamma-Ray Bursts and Broad-lined Supernovae with Close Binary Progenitors with Black Hole Central Engines

2025-06-17

Chris L. Fryer , Eric Burns , Anna Y. Q. Ho +5 more | The Astrophysical Journal

Abstract For over 25 yr, the origin of long-duration gamma-ray bursts (lGRBs) has been linked to the collapse of rotating massive stars. However, we have yet to pinpoint the stellar … Abstract For over 25 yr, the origin of long-duration gamma-ray bursts (lGRBs) has been linked to the collapse of rotating massive stars. However, we have yet to pinpoint the stellar progenitor powering these transients. Moreover, the dominant engine powering the explosions remains open to debate. Observations of both lGRBs, supernovae associated with these GRBs, such as broad-line (BL) stripped-envelope (type Ic) supernovae (hereafter, Ic-BL), supernovae (SNe), and perhaps superluminous SNe, fast blue optical transients, and fast x-ray transients, may provide clues to both engines and progenitors. In this paper, we conduct a detailed study of the tight-binary formation scenario for lGRBs, comparing this scenario to other leading progenitor models. Combining this progenitor scenario with different lGRB engines, we can compare to existing data and make predictions for future observational tests. We find that the combination of the tight-binary progenitor scenario with the black hole accretion disk engine can explain lGRBs, low-luminosity GRBs, ultra-long GRBs, and Ic-BL. We discuss the various progenitor properties required for these different subclasses and note such systems would be future gravitational-wave merger sources. We show that the current literature on other progenitor-engine scenarios cannot explain all of these transient classes with a single origin, motivating additional work. We find that the tight-binary progenitor with a magnetar engine is excluded by existing observations. The observations can be used to constrain the properties of stellar evolution, the nature of the GRB, and the associated SN engines in lGRBs and Ic-BL. We discuss the future observations needed to constrain our understanding of these rare, but powerful, explosions.

A Candidate for True Type-2 AGN without Hidden Central Broad-line Regions Identified by Central Tidal Disruption Event

2025-06-17

Ying Gu , Qi Zheng , P. Cheng +4 more | The Astrophysical Journal

Abstract In this manuscript, through applications of tidal disruption event (TDE) expected variability properties, a potential candidate for True Type-2 active galactic nuclei (TT2AGN) without hidden central broad-line regions (=TT2AGN) … Abstract In this manuscript, through applications of tidal disruption event (TDE) expected variability properties, a potential candidate for True Type-2 active galactic nuclei (TT2AGN) without hidden central broad-line regions (=TT2AGN) is reported in SDSS J233454.07+145712.9 (=SDSS J2334). Through analyzing the 20 yr optical light curves of SDSS J2334 from different Sky Survey projects, a TDE is preferred with a 4.7 M ⊙ main-sequence star tidally disrupted by the central black hole (BH) with mass 11.7 × 10 6 M ⊙ , indicating that central region within a distance of about 20 light days to the central BH in SDSS J2334 is directly in the line of sight. Moreover, active galactic nucleus (AGN) activities in SDSS J2334 can be confirmed through applications of (Baldwin, Phillips, & Terlevich (BPT) diagrams. Meanwhile, comparing virial BH mass determined through assumed broad Balmer emission components and M-sigma expected BH mass by well-measured stellar velocity dispersion through stellar absorption features, optical broad emission lines in SDSS J2334 are disfavored with confidence level higher than 6 σ . Therefore, combining the unique properties of the TDE and the spectroscopic results with only narrow emission lines, SDSS J2334 can be well identified as a potential candidate for a TT2AGN. The results indicate that to detect TDE expected flares in normal Type-2 AGN classified by spectroscopic results should be a new practicable method for identifying TT2AGN.

Evidence for GeV Gamma-Ray Emission from Intense GRB 240529A During the Afterglow’s Shallow Decay Phase

2025-06-17

Kenta Terauchi , Tomohiko Oka , Katsuaki Asano | The Astrophysical Journal

Abstract X-ray light curves of gamma-ray burst (GRB) afterglows exhibit various features, with the shallow decay phase being particularly puzzling. While some studies report the absence of the X-ray shallow … Abstract X-ray light curves of gamma-ray burst (GRB) afterglows exhibit various features, with the shallow decay phase being particularly puzzling. While some studies report the absence of the X-ray shallow decay for hyperenergetic GRBs, recently discovered GRB 240529A shows a clear shallow decay phase with an isotropic gamma-ray energy of 2.2 × 10 54 erg, making it a highly unusual case compared to typical GRBs. In order to investigate the physical mechanism of the shallow decay, we perform the Fermi-Large Area Telescope (LAT) analysis of GRB 240529A along with the Swift-X-Ray Telescope analysis. We find no jet break feature in the X-ray light curve and then give the lower bound of the collimation-corrected jet energy of >10 52 erg, which is close to the maximum rotational energy of a magnetar. Our LAT data analysis reveals evidence of GeV emission with a statistical significance of 4.5 σ during the shallow decay phase, which can be interpreted as the first case for hyperenergetic GRBs with a typical shallow decay phase. The GeV to keV flux ratio is calculated to be 4.2 ± 2.3. Together with the X-ray spectral index, this indicates an inverse Compton origin of the GeV emission. Multiwavelength modeling based on time-dependent simulations tested two promising models, the energy injection and wind models. Both models can explain the X-ray and gamma-ray data, while our modeling demonstrates that gamma-ray observations, along with future GeV–TeV observations by the Cherenkov Telescope Array Observatory, will distinguish between them.

Orbital Phase-resolved Analysis of X-Ray and Gamma-Ray Observations of the High-mass Gamma-Ray Binary 4FGL J1405.1−6119

2025-06-17

A. E. Lange , R. H. D. Corbet , Joel B. Coley +4 more | The Astrophysical Journal

Abstract We present the results of multiwavelength observations of the high-mass gamma-ray binary (HMGB) 4FGL J1405.1−6119. A pair of joint XMM-Newton and NuSTAR observations taken in 2019 (sampling the gamma-ray … Abstract We present the results of multiwavelength observations of the high-mass gamma-ray binary (HMGB) 4FGL J1405.1−6119. A pair of joint XMM-Newton and NuSTAR observations taken in 2019 (sampling the gamma-ray maximum and X-ray maximum) characterize the emissiong of soft and hard X-rays. We find variability of the hydrogen column density along our line of sight, N H , and photon index, Γ, and find no evidence of pulsations in X-rays. We also refine a new best-fit orbital period to P = 13.7157 ± 0.0014 days, the first orbital phase-resolved analysis based on nearly 16 yr of Fermi-LAT observations of 4FGL J1405.1−6119 and the evolution of the spectral shape as a function of orbital phase. Finally, the X-ray and gamma-ray spectra for the phases sampled in the new X-ray observations can be interpreted in the framework of the intrabinary shock model, previously applied to HMGBs such as LS 5039.

Two-component jet model for the afterglow emission of GRB 201216C and GRB 221009A and implications for jet structure of very-high-energy gamma-ray bursts

2025-06-17

Yuri Sato , Kohta Murase , Yutaka Ohira +2 more | Journal of High Energy Astrophysics

Newly Discovered Changing-look Active Galactic Nuclei from SDSS and LAMOST Survey

2025-06-16

Qian Dong , Zhi-Xiang Zhang , Wei‐Min Gu +2 more | The Astrophysical Journal

Abstract Changing-look active galactic nuclei (CL AGNs) exhibit drastic variations in broad emission lines (BELs), the mechanism of which remains unclear. Expanding the sample of CL AGNs is helpful to … Abstract Changing-look active galactic nuclei (CL AGNs) exhibit drastic variations in broad emission lines (BELs), the mechanism of which remains unclear. Expanding the sample of CL AGNs is helpful to reveal the mechanism. This study aims to identify more CL AGNs by crossmatching spectroscopic data from the Sloan Digital Sky Survey and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope. Our approach to identifying CL AGNs is based on automatic spectral fitting, followed by detailed visual inspections. We identify a sample of 51 CL AGNs through this method, in which 40 CL AGNs are newly discovered. Within this sample, 41 CL AGNs primarily show the variability of the H β line, nine exhibit obvious changes in both the H β and H α lines, and one source mainly displays variations in the H α line. Our findings reveal that the sequence of appearance and disappearance of the BELs aligns with the known CL sequence. In addition, we identify 31 candidates exhibiting drastic variations in BELs without accompanying significant photometric variability. We estimate the black hole mass and Eddington ratio for all sources, which range from 2.5 × 10 6 to 8.0 × 10 8 M ⊙ and from 0.001 to 0.13, respectively. Similar to other studies, we also find that the Eddington ratios of CL AGNs and candidates are lower than those of typical AGNs. Our results support the hypothesis that the CL behavior is driven by the state transitions of the accretion disk.

A New Shock in the Premerging Cluster Pair 1E2215-2216

2025-06-16

Yanling Chen , Liyi Gu , A. Simionescu +3 more | The Astrophysical Journal

Abstract The galaxy cluster pair 1E2216.0-0401 and 1E2215.7-0404 represents a major cluster merger in its early stages, a phase that has been scarcely explored in previous studies. Within this system, … Abstract The galaxy cluster pair 1E2216.0-0401 and 1E2215.7-0404 represents a major cluster merger in its early stages, a phase that has been scarcely explored in previous studies. Within this system, both axial and equatorial merger shocks have been identified. Recent XMM-Newton observations of the southern region of the cluster pair have increased the total exposure time to approximately 300 ks, enhancing the sensitivity to detect faint shock features in the cluster outskirts. Through a combined analysis of XMM-Newton and Chandra data, including both imaging and spectral techniques, a new shock front has been identified at approximately 2 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">′</mml:mi> </mml:mrow> </mml:mover> </mml:math> 3 south of the X-ray brightness peak of 1E2215. This shock front exhibits a surface brightness ratio of 1.33 ± 0.07 and a temperature ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1.2</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> in XMM-Newton, consistent with Chandra results. The Mach number, independently calculated from both the temperature and surface brightness discontinuities, yields consistent values of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi class="MJX-tex-calligraphic" mathvariant="script">M</mml:mi> <mml:mo>≈</mml:mo> <mml:mn>1.2</mml:mn> </mml:math> . The age, velocity, and spatial distribution of this shock suggest that it shares a common physical origin with the previously identified equatorial shock.

Cross-comparison of sampling algorithms for pulse profile modeling of PSR J0740+6620

2025-06-16

NULL AUTHOR_ID | Physical review. D/Physical review. D.

Radio bursts reveal universe’s ‘missing matter’

2025-06-16

| AAAS Articles DO Group

Dusty Stellar Source Classification by Implementing Machine Learning Methods Based on Spectroscopic Observations in the Magellanic Clouds

2025-06-16

Sepideh Ghaziasgar , Mahdi Abdollahi , Atefeh Javadi +7 more | The Astrophysical Journal

Abstract Dusty stellar point sources are a significant stage in stellar evolution and contribute to the metal enrichment of galaxies. These objects can be classified using photometric and spectroscopic observations … Abstract Dusty stellar point sources are a significant stage in stellar evolution and contribute to the metal enrichment of galaxies. These objects can be classified using photometric and spectroscopic observations using color–magnitude diagrams and infrared excesses in spectral energy distributions. We have employed supervised machine learning spectral classification to categorize dusty stellar point sources, including young stellar objects (YSOs) and evolved stars comprising oxygen- and carbon-rich asymptotic giant branch stars (AGBs), red supergiants (RSGs), and post-AGB stars (PAGBs) in the Large and Small Magellanic Clouds, based on spectroscopic labeled data derived from the Surveying the Agents of Galaxy Evolution (SAGE) project, which involved 12 multiwavelength filters and 618 stellar objects. Despite dealing with missing values and uncertainties in the SAGE spectral data sets, we achieved accurate classifications of these sources. To address the challenge of working with small and imbalanced spectral catalogs, we utilized the Synthetic Minority Oversampling Technique (SMOTE), which generates synthetic data points. Subsequently, among all the models applied before and after data augmentation, the probabilistic random forest (PRF) classifier, a tuned random forest, demonstrated the highest total accuracy, reaching 89% based on the recall metric in categorizing dusty stellar sources. In this study, using the SMOTE technique does not improve the accuracy of the best model for the CAGB, PAGB, and RSG classes; it stays at 100%, 100%, and 88%, respectively. However, there are variations in the OAGB and YSO classes. Accordingly, we collected photometrically labeled data with properties similar to the training data set and classified them using the top four PRF models with an accuracy of more than 87%. We also collected multiwavelength data from several studies to classify them using our consensus model, which integrates the four top models to present common labels as the final prediction.

The Effect of the Fast-flavor Instability on Core-collapse Supernova Models

2025-06-16

Tianshu Wang , Adam Burrows | The Astrophysical Journal

Abstract Merging our supernova code F ornax with the Box3D fast-flavor neutrino oscillation formalism, we explore the effects of fast-flavor conversion (FFC) in state-of-the-art one-dimensional (1D) and two-dimensional (2D) core-collapse … Abstract Merging our supernova code F ornax with the Box3D fast-flavor neutrino oscillation formalism, we explore the effects of fast-flavor conversion (FFC) in state-of-the-art one-dimensional (1D) and two-dimensional (2D) core-collapse supernova simulations. We find that after a few tens of milliseconds after bounce the FFC emerges just interior and exterior to the stalled shock wave. It does not obtain in the protoneutron star core nor near the average neutrinosphere radii. Interior to the shock, this results in a temporary change in the net neutrino heating rate of ∼10%, due mostly to a hardening of the ν e and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:math> neutrino spectra, despite the decrease in their corresponding neutrino number fluxes. In 1D, the hydrodynamic effects are not large, with increases in the stalled shock radius by of order 10 to 20 km that abate within a few hundred milliseconds. In 2D, the hydrodynamic effect of the FFC is a bit more noticeable, resulting in slightly earlier explosions for models for lower-mass progenitors but also potentially inhibiting explosions for some higher-mass progenitors. FFC continues to operate at larger radii at later times. The net result is a shift upward in the ν μ energy and number luminosities and a shift downward in the same quantities for both the ν e and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:math> neutrinos. There seems to be a trend at very large radii and later times toward partial species and spectral equipartition. If this is true, it could be an interesting feature of supernova neutrino detection at later times in underground and under-ice facilities.

Testing the cosmic distance duality relation using Type Ia supernovae and radio quasars through model-independent methods

2025-06-15

Fan Yang , Xiangyun Fu , Bing Xu +3 more | Chinese Physics C

Abstract In this work, we perform a cosmological-model-independent test on the cosmic distance duality relation (CDDR) by comparing the angular diameter distance (ADD) obtained from the compact radio quasars (QSOs) … Abstract In this work, we perform a cosmological-model-independent test on the cosmic distance duality relation (CDDR) by comparing the angular diameter distance (ADD) obtained from the compact radio quasars (QSOs) with the luminosity distance (LD) from the Pantheon Type Ia supernovae (SNIa) sample. The binning method and Artificial Neural Network (ANN) are employed to match ADD data with LD data at the same redshift, and three different parameterizations are adopted to quantify the possible deviations from the CDDR. We initially investigate the impacts of the specific prior values for the absolute magnitude $M_{\rm B}$ from SNIa and the linear size scaling factor $l$ from QSOs on the CDDR test, demonstrating that these prior values introduce significant biases in the CDDR test. To avoid the biases, we propose a method independent of $M_{\rm B}$ and $l$ to test CDDR, which treats the fiducial value of a new variable $\kappa\equiv10^{M_{\rm B} \over 5}\,l$ as a nuisance parameter and then marginalize its impact with a flat prior in the statistical analysis. The results show that the CDDR is consistent with the observational data, and QSOs can serve as a powerful tool for testing the CDDR independent of cosmological models.

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Spectroscopic and kinematic analyses of a warm survivor of a D6 supernova

2025-06-14

Mark Hollands , Ken J. Shen , R. Raddi +3 more | Monthly Notices of the Royal Astronomical Society

Abstract SDSS J163712.21+363155.9 is a candidate hyper-runaway star, first identified from its unusual spectrum in the Sloan Digital Sky Survey, which exhibits oxygen, magnesium, and silicon lines redshifted by several … Abstract SDSS J163712.21+363155.9 is a candidate hyper-runaway star, first identified from its unusual spectrum in the Sloan Digital Sky Survey, which exhibits oxygen, magnesium, and silicon lines redshifted by several 100 km s−1, leading to the suggestion it was ejected from a thermonuclear supernova. We have acquired GTC OSIRIS spectroscopy of SDSS J1637+3631 establishing a warm ($\rm{T_\mathrm{eff}}=15\, 680\pm 250$ K) carbon+oxygen dominated atmosphere, that is also abundant in the intermediate mass elements silicon, sulphur, and calcium. We interpret SDSS J1637+3631 as the donor to an accreting white dwarf that exploded in a dynamically-driven double-degenerate double-detonation (D6) type Ia supernova, where the current composition is consistent with a CO white dwarf core, enriched with intermediate mass elements from deposited supernova ejecta. While SDSS J1637+3631 has a low-precision Gaia parallax, our spectroscopic surface gravity (log g = 6.3 ± 0.3 dex) helps constrain its tangential velocity to $1950_{-530}^{+810}$ km s−1, providing additional support to the D6 mechanism. Under the assumption that SDSS J1637+3631 is a D6 survivor, we construct a kinematic model combining all astrometric, spectroscopic, and photometric information, but also including the structure and gravitational potential of the Milky Way. Our model localises the ejection site to the inner few kpc of the Galactic disc (though excluding the Galactic centre), with an ejection speed of $1870_{-300}^{+360}$ km s−1, and a $4.5_{-0.5}^{+0.4}$ Myr time of flight.

The Vlasov Equation Cannot Fully Account for Collisionless Shocks

2025-06-13

Antoine Bret | Contributions to Plasma Physics

ABSTRACT It is argued that the Vlasov equation cannot fully account for collisionless shocks since it conserves entropy, while a shock does not. A rigorous mathematical theory of collisionless shocks … ABSTRACT It is argued that the Vlasov equation cannot fully account for collisionless shocks since it conserves entropy, while a shock does not. A rigorous mathematical theory of collisionless shocks could require working at the Klimontovich level.

A Comparative Study of Euclidean and Spherical Clustering Techniques for BATSE Gamma-Ray Burst Data

2025-06-13

Prithwish Ghosh | Monthly Notices of the Royal Astronomical Society

Abstract This study investigates the classification of Gamma-Ray Bursts (GRBs) using spherical clustering techniques, focusing on the BATSE dataset with features T90, hardness, and F1. Spherical k-means and von Mises-Fisher … Abstract This study investigates the classification of Gamma-Ray Bursts (GRBs) using spherical clustering techniques, focusing on the BATSE dataset with features T90, hardness, and F1. Spherical k-means and von Mises-Fisher model-based clustering effectively recover the Long, Short, and Intermediate GRB classes, achieving high Adjusted Rand Index (ARI) of 0.65 and Normalized Mutual Information (NMI) of 0.50, with silhouette scores of 0.70-0.74 and Linear Discriminant Analysis (LDA) accuracies of 0.97-0.98. These methods outperform traditional Euclidean approaches, such as Gaussian Mixture Model-Based Clustering (GMMBC) and standard k-means, which yield accuracies of 72.38 per cent and 68.57 per cent, respectively, compared to 97.92 per cent for von Mises-Fisher and 90.11 per cent for spherical k-means. The optimal number of clusters, determined to be three using elbow and curvature-based methods, supports the tripartite classification proposed by Horváth. (1998). Spherical clustering’s robustness to magnitude variations, driven by cosine similarity, mitigates biases from cosmological and instrumental effects, providing clearer class separation. The intermediate GRB class, particularly well-defined by the von Mises-Fisher method, exhibits unique spectral and directional properties, potentially linked to neutron star-white dwarf mergers, as supported by observations like GRB 170817A. Exploratory analysis of Galactic coordinates hints at spatial clustering, possibly reflecting cosmic structure. These findings challenge the traditional GRB dichotomy and advocate for incorporating the intermediate class into physical models. Future work will integrate redshift measurements and multi-wavelength observations to further validate and refine these classifications.

CNN-Derived Elemental Abundances of LAMOST DR10 Giants: Implications for Galactic Substructures

2025-06-13

Haoyang Liu , Cuihua Du , Mingji Deng +1 more | Monthly Notices of the Royal Astronomical Society

Abstract Stellar parameters and abundances provide crucial insights into stellar and Galactic evolution studies. In this work, we developed a convolutional neural network (CNN) to estimate stellar parameters: effective temperature … Abstract Stellar parameters and abundances provide crucial insights into stellar and Galactic evolution studies. In this work, we developed a convolutional neural network (CNN) to estimate stellar parameters: effective temperature (Teff), surface gravity (log g) and metallicity (both [Fe/H] and [M/H]) as well as six α-elements (C, N, O, Mg, Si, Ca) and [α/M]. We selected giant stars with 3500 K &lt; Teff &lt; 5500 K and 0 dex &lt; log g &lt; 3.6 dex from the LAMOST and APOGEE surveys, while requiring (S/N)g of the LAMOST low-resolution spectra &gt; 10, which leaves 1 100 858 giant stars. The spectral from LAMOST and the labels from APOGEE for 62 511 common stars were used as our training set. The corresponding test set yields scatters 50 K, 0.06 dex and 0.13 dex for Teff, [Fe/H] and log g, respectively. For α elements O, Mg, Si and Ca, the scatters are 0.05 dex, 0.04 dex, 0.03 and 0.04 dex, respectively. For C and N elements, the scatters are 0.07 dex and 0.05 dex. For [α/M] and [M/H], the scatters are 0.03 dex and 0.06 dex. The mean absolute error (MAE) of most elements are between 0.02–0.04 dex. The predicted abundances were cross-matched with previously identified substructures PG1 and PG2, with their origins subsequently analyzed. Finally, the catalog is available at: https://nadc.china-vo.org/res/r101529/.

Possibility of multi-TeV secondary gamma rays from GRB221009A

2025-06-13

NULL AUTHOR_ID | Physical review. D/Physical review. D.

CMB Multipole Expansion in a Frame Dragging-Sustained Milky Way

2025-06-13

Federico Re , Marco Galoppo , Massimo Dotti | Galaxies

We study the impact on the cosmic microwave background (CMB) landscape of peculiar rotational general relativistic effects. These effects, on galactic scales, do not possess a Newtonian analogue, and therefore … We study the impact on the cosmic microwave background (CMB) landscape of peculiar rotational general relativistic effects. These effects, on galactic scales, do not possess a Newtonian analogue, and therefore could a priori impact CMB analysis. We find that the velocity inferred from the CMB dipole, under the kinematic interpretation, coincides with that measured by a stationary observer within the Milky Way and not with the one measured by the zero angular momentum observer. We show that the galaxy peculiar frame-dragging effects do not impact the standard CMB analysis, as these modify the multipole coefficients only at higher orders with respect to the dominant terms. Moreover, we prove that no general relativistic framework at the galactic scale patched within the standard cosmological model can account for the current tension on the CMB quadrupole amplitude.

Interacting binaries as a significant progenitor channel for Type II-P supernovae

2025-06-12

Ning-Chen Sun , Zexi Niu , Emmanouil Zapartas +7 more | Research Square (Research Square)

<title>Abstract</title> Type II-P supernovae (SNe II-P) are the most common class of core-collapse SNe in the local Universe. While their progenitors have long been assumed to follow single-star evolution, recent … <title>Abstract</title> Type II-P supernovae (SNe II-P) are the most common class of core-collapse SNe in the local Universe. While their progenitors have long been assumed to follow single-star evolution, recent theoretical studies suggest that 30–50% of all SNe II-P may instead originate from interacting binaries. These studies point to a potential paradigm shift in our understanding of this major SN class, but conclusive observational evidence still remains scarce. We propose that the possible binary origin for a SN II-P can be constrained through a combined analysis of direct progenitor detection, light-curve properties, and host environment. Applying this approach to 15 nearby SNe II-P, we identify 4 events (SN 2004A, SN 2012aw, SN 2018gj and SN 2020jfo) with likely binary origins: while the directly detected progenitors resemble those of other SNe II-P in terms of effective temperature and luminosity, they are located in old environments and/or have abnormal plateau lengths in the light curves. These characteristics are best explained if their progenitors have experienced significant binary interaction, which extends the lifetime far beyond what single-star models would predict and, under many circumstances, alters the final structure of the progenitor stars. Our results show that at least 27% of SNe II-P originate from the binary progenitor channel and robustly establish interacting binaries as a viable and significant pathway toward SNe II-P.

Observation and Simulation of Mutual Approximations between Five Main Uranian Satellites

2025-06-12

Jian Chen , Hao-Ran 浩冉 Song 宋 , Ye Yuan +4 more | The Astronomical Journal

Abstract Mutual approximation is an emerging method for obtaining high-precision astrometric measurements of natural satellites and asteroids. We used the 80 cm YaoAn High Precision Telescope to observe mutual approximation … Abstract Mutual approximation is an emerging method for obtaining high-precision astrometric measurements of natural satellites and asteroids. We used the 80 cm YaoAn High Precision Telescope to observe mutual approximation events of the main Uranian satellites during the period from 2021 to 2023. The average of internal errors along the directions of apparent relative motion and position are 20.0 and 5.1 mas, respectively. On the other hand, the rms of differences between observational results and the Jet Propulsion Laboratory ephemeris along the direction of apparent relative motion and position are 42.5 and 20.6 mas, respectively. We also investigated the factors affecting astrometric precision and found two simple indicators to exclude the invalid mutual approximation events, i.e., the events that do not contribute to precision enhancement. One indicator is the impact parameters divided by the difference of two satellites’ apparent semimajor axes; the other is the apparent relative velocity divided by the difference of their apparent orbital velocities. The resulting quotients of all invalid events are significantly larger than 1.1. Simulations confirm that the indicators are suitable for all the main Uranian satellites' mutual approximation events in recent years and the near future. Consequently, it is recommended to exclude invalid events from future observation campaigns by using the two indicators.

Supernova-Based Redshift Duality Test with Standard ΛCDM Parameters

2025-06-12

Tae-Kyoung Lee | Research Square (Research Square)

<title>Abstract</title> We propose a hybrid luminosity distance model that incorporates standard metric expansion alongside an additional redshift component, theoretically motivated by processes such as photon tunneling and the Breit–Wheeler process. … <title>Abstract</title> We propose a hybrid luminosity distance model that incorporates standard metric expansion alongside an additional redshift component, theoretically motivated by processes such as photon tunneling and the Breit–Wheeler process. This reinterpretation attributes part of the observed redshift to effective energy attenuation arising from an additional, possibly hidden, physical mechanism. Applied to the Pantheon+SH0ES Type Ia supernova dataset, the hybrid model—with the Planck-inferred parameters held fixed—was evaluated via least-squares regression and demonstrated superior statistical performance compared to the ΛCDM-only baseline, with ΔBIC = -6.67 and ΔAIC = -12.11. The attenuation coefficient, σₑ, representing the probability of quantum-induced photon loss per megaparsec, remains stable across redshift bins, implying a homogeneous effect. This minimal quantum–geometric hybrid framework offers a potential pathway toward alleviating the Hubble tension, while supporting the foundational assumptions of the ΛCDM model such as the constancy of ΩΛ and large-scale homogeneity. Moreover, it reveals hidden quantum contributions to cosmological observables.

Alien Type Ia Supernovae from the Milky Way Merger History and One Possible Candidate: Kepler’s Supernova

2025-06-12

Wei-bo He , Ping Zhou , Eda Gjergo +1 more | The Astrophysical Journal

Abstract The Milky Way is a dynamic and evolving system shaped by numerous merger events throughout its history. These mergers bring stars with kinematic and dynamic properties differing from the … Abstract The Milky Way is a dynamic and evolving system shaped by numerous merger events throughout its history. These mergers bring stars with kinematic and dynamic properties differing from the main stellar population. However, it remains uncertain whether any of the Galactic supernova remnants can be attributed to such a merger origin. In this work, we compare the progenitor of Kepler’s supernova to its nearby stars, “alien” stars, and in situ Milky Way stellar populations. We uncover the abnormal kinematics and dynamics of Kepler’s supernova and propose that its progenitor may have an extragalactic origin. We call the Type Ia supernovae (SNe Ia) produced by stars accreted into the Milky Way through merger events “alien SNe Ia” since they are cosmic immigrants. We estimate the rate of alien SNe Ia exploded recently using two methods: through galactic chemical evolution, and through a method without considering exact star formation history, introduced for the first time in this paper. We consider the past accretion of a few major satellite galaxies—Kraken, Gaia–Enceladus–Sausage, the Helmi streams, Sequoia, Sagittarius, Wukong/LMS-1, and Cetus—assuming these were dry mergers. The first method yields 1.5 × 10 −5 –5.0 × 10 −5 yr −1 , while the second method yields a comparable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mn>3.1</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.8</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mn>0</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>5</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mi>yr</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> as the rate estimates for recent alien SNe Ia. These estimates represent lower bounds because we assumed no postmerger star formation.