Formation and evolution of binary stars may have the same mechanism in different galaxies

(ORDO NEWS) — A research team led by Professor Qian Shengbang and graduate student Li Fuxing from the Yunnan Observatories of the Chinese Academy of Sciences found that the formation and evolution of massive binary stars in the Milky Way and the Andromeda Galaxy (M31) may follow the same mechanism.

Massive binary stars contain at least one early-type star whose spectral type is O, B-type. Such binars emit high-energy radiation, such as X-rays, and can create neutron stars or black holes.

When these systems evolve to a critical state where the mass ratio is equal to one (double binars), this binary has the shortest orbital period. Then the mass ratio in the biner will change to the opposite, there will be a transfer from a less massive component to a more massive one.

The researchers studied the evolutionary stage of V375 Cassiopeia (V375 Cas), a massive binary star containing two B-type components.

They analyzed the light curves of V375 Cas and found that it must undergo a late mass transfer from a less massive component to a more massive one.

The researchers also found two massive nearby binary galaxies with binary 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 those of the Milky Way.

Meanwhile, according to statistics, these massive semi-separated binaries have a third body with different periods. Judging by the HR diagram, the massive binar components are practically main sequence stars, and the evolutionary age of the secondary component is greater than that of the primary component for V375 Cas.

Based on the study of changes in the orbital period from OC diagrams and configurations of binars, the researchers found that these massive binary binars are at different stages of evolution with similar mass ratios (close to one).

The double contact binary is about to enter a critical stage of evolution with the shortest period and rapid mass transfer. The semi-separated binar has gone through this stage of evolution and cannot form a contact binar at the stage of declining orbit with mass transfer in case A.

The evolution of massive binars is equally possible in the Milky Way and M31, and these binars at a special stage provide an ideal testing ground for evolutionary models of massive binars.


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