Mass transfer in detached binaries : from mass-losing cool evolved stars to wind-fed compact objects

Séminaire IPAG de Ileyk El Mellah (IPAG), jeudi 14 janvier 2021, 11h00, IPAG seminar room

Once stars leave the main sequence, their evolution is largely set by mass loss through dust-driven or radiation-driven winds for cool and hot stars respectively. An illustration of the former is given by low and intermediate mass stars on the asymptotic and red giant branch, while a typical example of the latter are blue supergiants and Wolf-Rayet stars. Stellar multiplicity has been recognized as a ubiquitous feature : stars seldom live an effectively single life. In the advanced evolutionary stages, mass transfer via stellar winds can become significant and decide the final fate of both bodies. In high mass X-ray binaries, believed to be progenitors of merging compact objects, a blue supergiant is in close orbit with a neutron star or a black hole which captures a fraction of the stellar wind. On the other hand, non-spherical features in the dusty envelope surrounding cool evolved stars betray the presence of a stellar or planetary companion too dim to be directly detected but which shapes the outflow up to scales much larger than the orbital separation. The short orbital periods at stake in high mass X-ray binaries enable us to follow the compact object along its orbit with time resolved X-ray spectroscopy. While in detached binaries containing a red giant star, the orbital separation is large enough to image the circumbinary envelope and characterize its 3D morpho-kinematics.

In this talk, I will focus on the twofold benefit which can be obtained from crossed models of these complementary detached binaries where the donor star does not fill its Roche lobe. With the mesh-based radiative-hydrodynamics MPI-AMRVAC code, we designed a versatile setup suitable to capture the expansion of both a line and a dust-driven wind impacted by the gravitational influence of a companion. In numerical simulations of high mass X-ray binaries, we can follow the accretion flow over several orders of magnitude and use the compact object as an orbiting X-ray probe to constrain the micro-structure of the highly inhomogeneous stellar wind. Around cool evolved stars, these simulations shed a new light on the complex and diverse morphology of the envelope unveiled by ALMA. In both cases, we will describe how mass transfer redistributes angular momentum and can lead to orbital inspiral.