2024/11/21 by Jaroslav Merc, Henri M. J. Boffin · 1 voice
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Asymptotic giant branch #Binary number #Binary star #Binary system #Common envelope #Interferometry #Physics #Red giant #Roche lobe #Stars #Stellar, planetary, and galactic studies #White dwarf #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/202451952
arxiv published 2024/11/21 · arxiv updated 2024/11/21 · openalex publication_date 2024/11/25 · openalex created_date 2024/11/26 · openalex updated_date 2026/07/28
While mass transfer in binary systems is a crucial aspect of binary evolution models, it remains far from understood. HD 352 is a spectroscopic binary exhibiting ellipsoidal variability, likely due to a tidally deformed giant donor filling its Roche lobe and transferring matter to a faint companion. Here, we analyze VLTI/PIONIER interferometric observations of the system, obtained between 2010 to 2020. We demonstrate that observations near the system’s quadrature cannot be explained by simple symmetric disk models, but they are consistent with the shape of a Roche-lobe-filling star. We think that this is the first case of tidal deformation of a red giant being observed directly, thanks to the interferometric technique. By combining our interferometric modeling results with the analysis of the optical spectrum, multifrequency spectral energy distribution, and published radial velocities and light curves, we constrained the system parameters and show that HD 352 will likely soon enter the common envelope phase, although we cannot reject the hypothesis that it is undergoing stable mass transfer against theoretical predictions. This has important consequences for modeling a large class of binary systems. Additionally, our observations confirm that Roche-lobe-filling giants can be resolved with interferometry under favorable conditions. Such observations may help resolve the mass transfer dichotomy in systems such as symbiotic binaries, where the predominant mass transfer mode remains unclear.