Scientists explore the evolution of the X-ray binary system GX 301-2

(ORDO NEWS) — Astronomers from Argentina and France have been investigating the evolutionary history of the high mass eccentric X-ray binary known as GX 301-2.

The results of the study, provide important information about the origin of this object and may help scientists better understand the evolution of X-ray binaries in general.

X-ray binaries consist of an ordinary star or white dwarf giving mass to a neutron star or black hole.

Based on the mass of the companion star, astronomers divide them into low mass X-ray binaries (LMXB) and high mass X-ray binaries (HMXB).

GX 301-2 is located approximately 10,000 light years from Earth. This is an X-ray binary discovered in 1973.

It consists of a compact object and the star Wray 977, which is a supergiant with a mass in excess of 31 solar masses, making GX 301-2 a high-mass X-ray binary.

GX 301-2 shows X-ray pulsations with a period of 11.6 minutes. Its orbital period is approximately 41.5 days. This is one of the most eccentric HMXB systems known to date.

A team of astronomers studied the special properties of GX 301-2, focusing on the origin and evolutionary history of this system. For this purpose, scientists used the MESA stellar evolution code.

The study showed that in a high accretion efficiency scenario in the GX 301-2 system, the neutron star progenitor would have transferred most of its envelope to its companion Wray 977.

The astronomers calculated that the mass of the progenitor was in the range of 23-30 solar masses, and that the initial mass ratio system was 0.8–0.9.

Higher initial masses would most likely lead to the formation of a black hole.

Data regarding the masses of the progenitor stars indicate that the initial orbital period was less than five days.

If the orbital period were longer, then accretion would be insufficient to increase the mass of the companion.

Moreover, an initial orbital period of less than two days is also undesirable, since in this case the star will not be able to reach the core collapse stage.

Summing up, the authors of the article emphasized the unique properties of the GX 301-2.

The scientists said the chances of finding an HMXB in the Milky Way with properties similar to those found in GX 301-2 are extremely low.


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