PhD student SHI Xiangdong, Prof. QIAN Shengbang et al., from Yunnan Observatories of the Chinese Academy of Sciences, analyzed the magnetic activity of interacting binaries. They found that the variation of light curve of KIC 06852488 is strongly correlated with the variation of O-C curve, and first found that the positions of dark spot and hot spot are symmetrical with the inner Lagrange L1 point, which reveals the important influence of stellar magnetic activity on the mass transfer of the binary. This result was published in The Astronomical Journal recently.

Algol-type binary systems consist of a B-A-F type main-sequence primary component and an F-G-K type giant or subgiant secondary component. According to the explanation of the Algol paradox, the initially more massive component evolves to fill the Roche lobes first and transfer material to another component, which results in the inversion of mass ratio and the formation of the Algol-type systems. Hence, mass transfer plays an important role in the evolution of this kind of binary system.

In this study, researchers analyzed KIC 06852488. Its primary component is a δ Sct-type pulsating star in the main-sequence stage, and its secondary component is a late-type component with a strong magnetic activity. It is found that the variation of the two maxima in the light curve are related with a same cycle length ~2000 days and a 180°phase difference, and the variation of the secondary maxima coincides with the O-C curve of primary light minima.

After analyzing the Kepler and TESS (Transiting Exoplanet Survey Satellite) light curves, it is detected that this binary is a semi-detached system with a mass ratio 0.46. The secondary component is filling its critical Roche lobe. The variation of the O'Connell effect could be explained by an evolving hot spot on the primary component and an evolving cool spot on the secondary component, and their positions are almost symmetrical with the inner Lagrange L1 point.

Researchers found that the positions of hot spot and cool spot are symmetrical, which reveals that the mass transfer of the binary may be related to the magnetic activity. After subtracting the binary brightness changes, six optical flares are detected. The flares, pulsation of component, mass transfer and spot activity make the system a natural Astrophysics Laboratory for studying the interaction of binary mass transfer, stellar pulsation and magnetic activity. (within 10 days)

 Contact:

SHI Xiangdong

Yunnan Observatories, CAS

sxd@ynao.ac.cn