X-RAY OBSERVATIONS OF VERY FAINT X-RAY TRANSIENTS (VFXTS) VERSUS BRIGHT X-RAY TRANSIENTS
Nordita Astrophysics seminars
Wednesday 23 May 2018
to 14:30 at
Aru Beri (Southampton U)
Low mass X-ray binaries (LMXBs) contain a black hole or neutron star that accretes matter from a companion star which typically has a mass lower than that of the accretor. Most low mass X-ray binaries are transients which means they undergo outbursts sporadically. During an outburst, the X-ray luminosity can increase up to a few times 1037-1039 ergs/s (bright outbursts). These outbursts are thought to be triggered by the thermal-viscous instability in a thin accretion disk. In the last 15 years, it has been found that there are LMXBs which show sub-luminous accretion outbursts, i.e., having peak outburst luminosities within a range of 1034-1036 ergs/s. This class of LMXBs is known as very faint X-ray transients~(VFXTs). These faint outbursts are believed to occur due to radiatively inefficient accretion. One of the challenging aspect in the study of these very faint X-ray transients is to understand the nature of a compact object. Here, in this talk I will discuss a detailed study of two VFXTs, namely; MAXI J1957+032 (J1957) and Swift J1357.2-0933 (J1357). I will also present results of one of the brightest LMXB transient, MAXI J1535-571 (J1535) observed with AstroSat. Radio and X-ray follow up observations showed that this system is a low-mass X-ray binary containing a black hole.