Type: Article
Publication Date: 2024-04-03
Citations: 3
DOI: https://doi.org/10.1051/0004-6361/202348755
Context . High-order multiple (triple and beyond) systems are relatively common. Their interaction with circumstellar and circumbinary material can have a large impact on the formation and evolution of planetary systems and depends on their orbital properties. Aims . GG Tau and UX Tau are two pre-main sequence high-order multiple systems in which the tightest pair has a projected separation of ≈5–20 au. Characterizing precisely their orbits is crucial to establish their long-term stability, to predict the dynamics and evolution of circumstellar matter, and to evaluate the potential for planet formation in such systems. Methods . We combine existing astrometric measurements with previously unpublished high-resolution observations of the GG Tau Ab and UX Tau B pairs and perform Keplerian orbital fits. Results . For GG Tau Ab the data presented here represent the first detection of orbital motion. For both systems they yield dramatic increases in orbital coverage (≳60% and ≈100% for UX Tau B and GG Tau Ab, for orbital periods of ≈32 and ≈8 yr, respectively) and allow us to obtain well-constrained orbital fits, including dynamical masses with ≲10% and ≲7% random and systematic uncertainties. We find that both GG Tau A and UX Tau A–B likely form stable hierarchical systems, although one possible deprojection solution for GG Tau is strongly misaligned and could experience von Zeipel-Lidov-Kozai oscillations. We further find that the UX Tau B orbit is much more eccentric than the GG Tau Ab one, possibly explaining the lack of circumstellar material in the former. Conclusions . The newly-determined orbits revive the question of the dynamical fate of gas and dust in these two hierarchical systems and should spur new dedicated simulations to assess the long-term evolution of the systems and the dynamical perturbations imposed by the close binaries they host.