Recently, Dr. LI Linjia and Prof. QIAN Shengbang from Yunnan Observatories of the Chinese Academy of Sciences studied the pulsation characteristics of a c-type RR Lyrae star, BE Dor, and found that its pulsation period showed quasi-periodic variation and abrupt change. The results of this work are published in Monthly Notices of the Royal Astronomical Society.

In the observation, the pulsation modulation phenomenon of RR Lyrae stars is common, which is known as Blazhko effect. This effect is usually represented by the modulations of pulsation period and amplitude. However, it is found that there are special modulation phenomena in the pulsations of some c-type RR Lyrae stars: the period modulation is significant, but there is no corresponding change in the pulsation amplitude. BE Dor is the star showing this phenomenon.

The research team used the data of several photometric sky survey projects (DASCH, MACHO, OGLE, ASAS-SN and TESS) to analyze BE Dor in detail. Adopting the O-C method and Fourier method, they found that the pulsation period showed quasi-periodic variation and abrupt change. The former may be related to the solar-like magnetic field activity, and the latter may correspond to the sudden change of the magnetic field.

The research team also studied the pulsation properties of the other four c-type RR Lyrae stars in Kepler field, and found that the intensity of the pulsation period changes is positively correlated with the macro-turbulence velocity. The research team speculated that the modulations in BE Dor and some other c-type RR Lyrae stars are the results of the interaction of turbulent convection and magnetic field activities, i.e., the viewpoint of Stothers, Richard B.

Combined with the pulsation properties of other similar types of variable stars, the researchers pointed out that the mechanism for the modulations is related to the turbulent convection in the hydrogen-helium ionization envelope. They proposed that the modulation showing in BE Dor should be the result of the interaction of the solar-like magnetic field activity and macro-turbulence.

Contact:
LI Linjia, Yunnan Observatories, CAS
lipk@ynao.ac.cn