MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

Astronomy & Astrophysics 55 increases during the burst, probably due to the burst mechanismcausing an increase in the accretion rate. The study of black holes, ranging from stellar mass to themassive ones seen in the centres of galaxies is an area of great interest to Indian astronomers. Several groups are involved in theoretical studies of these objects. The application of the theoretical models to explain several observational phenomenon related to accreting black holes include (a) the development of a general relativistic model of jet variability in active galactic nuclei due to orbiting blobs in helical motion along a funnel or cone shaped magnetic surface anchored to the accretion disk near the black hole, (b) development of a detailed model for an explanation of the tidal disruption events (TDEs), constructed using stellar dynamical and gas dynamical inputs that include black hole mass, specific orbital energy and angular momentum, star mass and radius, and the pericenter of the star orbit, and (c) development of theoretical models for light curves of X-ray binaries to investigate the changes in the light from such systems, by taking into consideration the self-rotation and tidal effects due to the presence of the secondary component. AstroSat-LAXPC has been used to detect X-ray pulsations inmultiple Be/X-ray binaries at hard X-ray energies for the first time. Broadband X-ray spectra in the 0.7-20 keV range, obtained usingAstroSat's SXT and LAXPC, of multiple black hole X-ray binaries were fitted to extract the nature of the disc emission and other parameters such as the inner radius of the disc, accretion disc, and BH spin. Another X-ray binary was observed during a transition of spectral state accompanied by an increase in radio emission, as has been observed in similar sources before, which indicates a connection between emergence of radio jet and the change in accretion disc structure. Spin phase dependence of X-ray polarisation in CrabNebula was detected and studied for the first time usingAstroSat-CZTI. Indian astronomers, in collaboration with an international team, have demonstrated that certain spectral and emission features of a large sample of BH X-ray binaries are significantly different from that of the neutron star binaries. The above observation showed that the BH systems behave differently from those containing neutron stars, and argued that the difference is due to the latter having a solid surface as opposed to an event horizon in the former.While existence of BHs has been proven beyond reasonable doubt, clear signature of an event horizon has been elusive, and the above workmay finally provide themuch-awaited purely data driven proof of its existence. The possibility of accreting primordial black holes as the source of heating for the collapsing gas in the context of the direct collapse black hole scenario for the formation of super-massive black holes at high redshifts (z~ 6 - 7) was -2 10 M can heat collapsing gas to an explored. It was shown that primordial black holes with masses greater than ʘ extent that H formation is inhibited. 2 4.1.15 ActiveGalactic Nuclei All galaxies have a SMBH at their center. In a few percent of the galaxies, the SMBH is accreting mass from its surroundings at a very high rate, and part of the gravitational energy released by the accreted matter is radiated causing the center of these galaxies to be extremely luminous. These are called active galactic nuclei (AGN). The X-ray spectra of AGN have been characterized in detail by Indian astrophysicists to identify the emission mechanisms responsible for various components in it. They were involved in the discovery of the so-called “soft X-ray excess” in the power-law X-ray spectrum of Seyfert galaxies and have investigated its physical origin using both spectral analysis and flux variability. Evidence for reprocessing of coronal X-ray emission in the accretion disk ofAGN, which MEGA SCIENCE VISION-2035