|Time:||星期二, 12月 15, 2020, 10:30am|
|Title:||Mass tranfer in AGB binaries - uncovering a new evolution channel by simulations|
|Speaker:||Dr. Zhuo Chen (DoA postdoc)|
The origin of chemically peculiar stars and non-zero eccentricity in evolved close binaries have been long-standing problems in binary stellar evolution. Answers to these questions may trace back to an intense mass transfer during an AGB binary phase.
In this talk, the speaker will discuss two mass transfer modes in the AGB binaries and the transition between them. One mass transfer mode is Bondi-Hoyle-Lyttleton (BHL) accretion and the other is Wind-Roche-lobe overflow (WRLOF). They use AstroBEAR to solve radiation-hydrodynamic equations in 3D and calculate mass transfer rates in asymptotic-giant-branch (AGB) binaries with different binary separations. Accretion disks may form around the secondaries. Depending on the binary separation, a circumbinary disk or a spiral structure may appear in the simulation. The resulting mass transfer efficiency in our models is up to a factor of 8 times higher than what
the standard BHL accretion scenario predicts, and the outflow gains up to 91% of its initial angular momentum when it reaches 1.3 binary separations. Consequently, some AGB binaries may undergo orbit shrinkage, and some will expand. The high mass transfer efficiency is closely related to the presence of the circumbinary disks.
Zhuo Chen is TAO fellow and Shuimu scholar at the DoA at Tsinghua University. Prior to this position, he was a CITA National fellow at the University of Alberta. He earned his Ph.D. from the University of Rochester in 2018. His primary interest is applying more self-consistent radiation-hydrodynamic models to various astrophysical problems, e.g., accretion process, binary evolution, and stellar atmosphere.