With AstroSat, astronomers from India reveal features of the X-ray binary system in space


Astronomers from India have observed an X-ray binary system in space known as GRS 1915 + 105 using AstroSat, the first dedicated Indian astronomy mission. At a distance of about 28,000 light years from Earth, this system is a superluminal low mass X-ray double system (LMXB). It was first discovered in August 1992. However, AstroSat observations confirmed that it has different types of variability classes. It can move from one class to another in a matter of hours. The system has a cycle time, the time required for one rotation, of 33.5 days.

Its black hole is estimated to be about 13 times the mass of the Sun. X-ray binary systems (XRB) consist of a normal star or white dwarf that transfers mass to a small neutron star or black hole. Based on the mass of the companion star, XRBs are classified as low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs).

Astronomers found that the changes in X-ray intensity from GRS 1915 + 105 resembled the light curve of a “canonical” erupting black hole. However, they also found that, unlike canonical sources, this system does not follow the exemplary ‘q’ diagram on the hardness-intensity diagram (HID), according to a report on Phys.org, an online science, research and news bulletin Technology aggregator.

Earlier observations have shown that GRS 1915 + 105 has a wide range of variability in its light curve – so far 15 classes. To learn more about the system, a team of astronomers led by Athulya Menon of Dayananda Sagar University in Bengaluru decided to use AstroSat to study the source.

“In this paper, we conduct an in-depth analysis of 31 AstroSat observations from GRS 1915 + 105 from November 2016 to June 2019 by examining the broadband ‘spectro-temporal’ properties of the source,” the researchers explained.

Thus, the behavior of GRS 1915 + 105 suggests that it will evolve towards an obscured phase of low luminosity, with a decrease in the intrinsic bolometric luminosity of the source due to obscuration.


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