A research team led by Prof. Qian Shengbang and Ph.D. student Li Fuxing of the Yunnan Observatories of the Chinese Academy of Sciences has discovered that the formation and evolution of the massive binary stars in the Milky Way and Andromeda Galaxy (M31) may share the same mechanism.
Their findings were published in Monthly Notices from the Royal Astronomical Society and The Astrophysical Journal†
Massive binary stars contain at least one early-type star whose spectral type is O, B-type. These binary stars have high-energy radiation, such as X-rays, and can neutron stars or black holes. The precursors of these semi-detached binary stars are the detached binary stars where the original, more massive components evolve faster and fill their critical Roche lobes first, then transfer mass to their companions with the case A evolution.
During this process, the system turnaround time will be shortened and the mass ratio: will be enlarged. When the system evolves to the critical condition where the mass ratio is equal to one (two binary numbers), this binary has the shortest orbital time. Then the mass ratio of the binary number is reversed with mass transfer from the less massive component to the more massive after this special stage.
In the study published in Monthly Notices from the Royal Astronomical Societythe researchers studied the evolutionary stage of V375 Cassiopeia (V375 Cas), a huge binary number containing two B-type components.
They analyzed the light curves of V375 Cas and found that V375 Cas should undergo a late case A mass transfer from the less massive component to the more massive one.
Meanwhile, according to the statistics, those huge semi-detached binaries have a third body with different periods. From the HR diagram, the components of the massive binaries are almost the main sequence stars, and the evolutionary age of the secondary component is greater than that of the primary for V375 Cas. “V375 Cas is a hierarchical triple system where a massive main sequence star is accompanied by a massive semi-detached mass transfer binary star based on the third light estimate,” said Li.
The researchers also discovered two huge close binaries with double components in M31. M31 is the closest spiral galaxy to the Milky Way and the largest galaxy in the Local Group, and its structure and metallicity are very close to that of the Milky Way.
The photometric solutions were performed using the WD method of 437 obscuring binary stars, and two double binaries were found. One system is a contact binary with a mass ratio of 0.974 and the other system is a semi-detached binary with a mass ratio of 0.924. This result suggests that the massive double binaries are rare in M31.
Based on the study of the changes in orbital periods through the OC diagrams and configurations of binary stars, the researchers found that these two massive double binaries are in different evolutionary stages with similar mass ratios (close to one). The double contact binary is about to enter the critical evolutionary stage of the shortest period of rapid mass transfer. The semi-detached binary has been through that stage of evolution and fails to form a contact binary during the orbital decreasing phase with case A mass transfer.
These findings were published in The Astrophysical Journal†
These two works indicate that the evolution of massive binary stars is similarly possible in the Milky Way and M31, and these binary stars at a special stage create an ideal testbed of evolutionary models of massive binary files†
FX Li et al, The massive system V375 Cassiopeia is a semi-detached binary mass transfer with a massive stellar companion, Monthly Notices from the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac1327
F.-X. Li et al, Two Massive Close Binaries with Twin Components in the nearby Galaxy M31, The Astrophysical Journal (2022). DOI: 10.3847/1538-4357/ac6c81
Chinese Science Academy
Quote: Formation and evolution of massive binary stars may share the same mechanism in Milky Way and Andromeda galaxies (2022, June 17) retrieved June 18, 2022 from https://phys.org/news/2022-06-formation-evolution-massive- binaries -mechanism.html
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