AstroSat's view of the newly discovered soft X-ray transient: MAXI J0637-430

Soft X-ray Transients (SXTs) are a subclass of Low-Mass X-ray binaries (LMXBs), which appear as extremely faint sources, if detected at all. They occasionally undergo sporadic outbursts, occurring at intervals of 1 - 50 years, which cause their X-ray luminosity to increase by a factor of 10$ ^{4}$ − - 10$ ^{6}$. This then decays back to quiescence with an e-folding timescale of $\sim$ 30 days. A remarkable property of SXTs is that their luminosity varies over a wide range (10$ ^{33}$ − - 10$ ^{38}$ ergs/s). This allows us to investigate accretion onto compact objects over a much larger range of luminosities, and therefore accretion rates. SXTs, while still poorly studied, are an important subclass of LMXBs, as they provide a unique opportunity to gain crucial insights to understand high energy astrophysical processes that drive the erratic state transitions that are drivers of the outbursts seen in them. MAXI J0637-430 is an SXT, first detected by the MAXI/GSC nova alert system during seven scan transits from 2$ ^{nd}$ - 3$ ^{rd}$ November, 2019. Follow-up observations in the X-ray, UV, optical and radio bands were carried out by several observatories. This source was also observed by the AstroSat mission, using the Large Area X-ray Proportional Counter and Soft X-ray Telescope instruments during its outburst decay, providing simultaneous coverage in the soft and the hard band in 0.7 - 80 keV range. We have carried out in-depth spectro-temporal studies of $\sim$ 40 ks data of MAXI J0637-430. Our analysis points out that the source underwent a spectral state transition during the observation. Further, we have made attempts to characterize its physical parameters and understand their evolution during the outburst decay. In addition to this, our studies shed light on the nature of the central compact object and constrain the properties of this newly discovered transient source. These results will be presented during the meeting.