Astronomy and Astrophysics Seminars

Black Hole X-ray transients across the mass scale

by Mr. Sudip Chakraborty (DAA, TIFR)

Tuesday, September 8, 2020 from to (Asia/Kolkata)
at Zoom link: ( Meeting ID: 945 0147 2851 ; Passcode: 910569 )
Meeting ID: 945 0147 2851 Passcode: 910569
Multiwavelength spectral and timing studies of transient black hole X-ray sources, both galactic (such as Low Mass X-ray Binary, LMXB) and extragalactic (such as Tidal Disruption Event, TDE), provide fantastic opportunities to probe strong gravity regime, to understand the accretion-ejection mechanism and to observe the evolution thereof. In the case of galactic Black Hole X-ray Binaries (BHXBs), the X-ray emission is attributed to an accretion disc, a non-thermal corona and an occasional jet. The interplay between the disc, corona and jet give rise to the spectral evolution of BHXBs, represented in terms of Hardness Ratio-Intensity diagram or 'q' diagram. With the advent of recent broadband X-ray telescopes, further complexities are being revealed. In the first part of this talk, I will present our past and present efforts on characterizing the complex broadband spectra of two such sources: MAXI J1820+070 and MAXI J1348-630. In the former, we investigate the possibility of a structured, multi-component corona; and in the latter, we probe the possibility of reflection from a high-density disc. Next, we will investigate the universality of black hole accretion from BHXBs to TDEs. For this purpose, we compare the simultaneous UV to X-ray emission from a sample of TDEs with a sample of AGN  of different masses and accretion rates,  and galactic  Black  Holes in the different states.  This not only gives us an idea about the place of TDE in the demographic of black hole accretion but also provide us with clues about late-time emission and evolution of TDEs.