Recently, PhD student LI Fuxing, Prof. QIAN Shengbang et al., from Yunnan Observatories of the Chinese Academy of Sciences discover 12 semidetached mass-transfer massive binaries from a total of 437 eclipsing binaries in Andromeda galaxy (M31), and the secondary (less massive) components filled their Roche lobes, while the more massive ones are detached from the lobes.

The facts indicate that these binaries are in the stage of slow mass transfer from less massive components to their companions, and the evolution of massive binaries in M31 is possible the same as that of the Milky Way. The result of this study was online published in The Astronomical Journal on April 8.

M31 is the closest spiral galaxy to the Milky Way and the largest galaxy in the Local Group. Its structure and metallicity are very close to that of the Milky Way. Since M31 is far away from the earth, most of the eclipsing binaries obtained in M31 are massive binaries, and only a few binaries have been investigated for the distance modulus of M31. Therefore, whether the structural characteristics and evolutionary state of these binaries are the same as those of massive binaries in the Milky Way, are poorly understood.

The light curves were from Vilardell et al. (2006), in which the photometric time series were observed by the 2.5 m Issac Newton Telescope in Spain. The photometric solutions were performed with the W-D method from 437 eclipsing binaries, and 12 semidetached binaries whose secondary components filled their Roche lobes have been found.

The relationship between the mass ratio and the fill-out factor of the primary star, reveals that they are in the stage of slow mass transfer from less massive components to their companions with the reversed mass ratio. Meanwhile, the temperature distribution of primary and secondary stars of these binaries is similar to that of semidetached binaries in the Milky Way.

These facts suggest that the evolution of massive binaries in M31 should be similar to that in the Milky Way, which provides a valuable test of the evolutionary models of mass transfer of massive binaries. (within 10 days)

Contact:

LI Fuxing, Yunnan Observatories, Chinese Academy of Sciences

lfx@ynao.ac.cn