The pulsating stars in eclipsing binaries are particular attractive objects for the study of stellar structure and evolution since they exhibit eclipses and pulsations simultaneously.

The orbital motion and light eclipse allow people to directly determine accurate stellar parameters such as mass and radius for each component. Asteroseismology, by reproducing the observed modes, offers people significant insight into the interiors of the star.

On June 4, The Astrophysical Journal published a theoretical study on an eclipsing binary. Dr. CHEN Xinghao from Yunnan Observatories of the Chinese Academy of Sciences and his collaborators discovered an Algol-type eclipsing binary KIC 10736223 that has just undergone the rapid mass-transfer stage.

As a typical classical Algol system, KIC 10736223 is formed through mass exchange and mass-ratio reversal. “By modeling the light curve, we found that the secondary star is almost filling its Roche lobe. That is very interesting, the feature probably indicates that the binary system just passed a rapid mass-transfer stage,” said Dr. ZHANG Xiaobin, one of the authors of this study.

In order to ascertain this discovery, the researchers constructed two grids of theoretical models to reproduce the pulsation frequencies. They found fitting results of mass-accreting models agree well with those of single-star evolutionary models. Also, they found that the pulsator is an almost unevolved star with an age between 9.46 and 11.65 Myr for single-star evolutionary models and 2.67–3.14 Myr for mass-accreting models.

Therefore, they identified KIC 10736223 to be an Algol system that has just undergone the rapid mass-transfer process.

"The mass-transfer process is still the largest uncertainties. The discovery of KIC 10736223 provides a new constraint on this process, and is of great scientific significance to improve the present theory of stellar structure and evolution,” said Dr. CHEN.