Recently, Dr. CHEN Xinghao from Yunnan Observatories of the Chinese Academy of Sciences and his cooperators discovered an Algol-type binary formed through an extremely helium-poor mass accretion. The result of this study was online published on The Astrophysical Journal on October 18.

OO Dra is an Algol-type eclipsing binary with delta Scuti-type pulsations, where the pulsating primary star is formed through accreting mass from its companion star, and the secondary star is still nearly filling its Roche lobe. Pulsational characteristics of delta Scuti stars in eclipsing binary are very similar to those of single pulsators, but their evolutionary tracks are distinctly different due to the influence of mass accretion process.

"We obtained seven independent pulsation frequencies based on 2-minutes Transiting Exoplanet Survey Satellite (TESS) data. Both eclipse and pulsation nature make OO Dra an ideal target for the study of mass exchange process,” said Dr. CHEN Xinghao.

Researchers reproduced those pulsation frequencies with the method of asteroseismology, and they found the pulsating primary star nearly unevolved and its surface helium abundance extremely poor. Through further helium-poor mass accreting modeling, they determined its age to be 0.14-0.67 Myr, further confirming that OO Dra just went through a helium-poor mass accreting process.

The mass-transfer process is still the largest uncertainties in theory of binary, and present theories often use helium-rich mass accreting process. The finding of OO Dra presents new challenges and constraints on this process, and is of great scientific significance to improve the theory of stellar structure and evolution.

Contact:

CHEN Xinghao, Yunnan Observatories, Chinese Academy of Sciences

chenxinghao@ynao.ac.cn