On the properties of dissipative shocks in the relativistic accretion flows

Abstract

In the present work, we study the properties of dissipative shocks for fully relativistic accretion flows around spinning black holes. In an accretion flow harboring a dissipative shock (formally known as radiative shock), a significant portion of the thermal energy may get released from the post-shock corona. A stellar-mass black hole may therefore emit hard X-rays from the inner edge of the disk. If the bulk energy loss is significant, post-shock pressure drops, and shock moves forward towards the black hole compressing the size of the post-shock corona, resulting an enhancement of the corona temperature and compression ratio. The dynamical properties of the radiative shocks are therefore systematically investigated to understand accurately the radiative loss processes, temporal variations, and the spectral properties. We notice that the range of flow parameters (e.g. energy and angular momentum) responsible for the formation of ‘shocks in accretion (SA)’ are identical for both the case of standing and dissipative shocks. The spin of the black hole enhances the dissipation further. We estimate the maximum energy release, which is observed close to $100\%$ in the extreme cases. This could be useful in explaining various observed phenomena namely the formation and the systematic evolution of QPOs, and the time lags in between hard and soft X-ray photons (e.g., XTE J1550-564 and GRO J1655-40 etc.) during their outbursts.

Study of Spectral State Transitions in Black Hole Binaries

“…Currently, in this investigation, we demonstrate the role of the second parameter (the size during the cooling of the corona) independently and extensively, irrespective of the first one (accretion rate). We estimate the variation of the energy dissipation from the Comptonizing medium when the accretion flow harbors a radiative/dissipative shock (Mondal & Basu 2020). Interestingly, we find a signature of the spectral transition during the post-shock cooling and have achieved theoretically the discontinuity in the emitted hard flux.…”

“…, the specific angular momentum, and (iii) spin (a) of the black hole. The full solution is given in Mondal (2010;Mondal & Basu 2020) and can also be found in the literature. The ranges of flow parameters ( l ,  ) presented in Figure 1 for a different spin (a) satisfy the shock conditions, and the accretion flow may harbor a shock.…”

“…The other shock conditions remain unchanged (Mondal & Basu 2020) between the pre-and post-shock branches but the energy conservation is violated during the shock transition. This differs from the standing shock conditions.…”

“…Hence, several attempts have been made to study the radiative or dissipative shock in black hole accretion physics (Das et al 2010;Singh & Chakrabarti 2011a, 2011bFragile et al 2012;Singh & Chakrabarti 2012;Sarkar & Das 2013;Nagarkoti & Chakrabarti 2016;Mondal & Basu 2020) so far. Following the same line, we consider here the relativistic accretion flows where the disk is sub-Keplerian as assumed in the Two Component Advective Flow(TCAF) model with shocks, and thus, this paper does not deal with the flow of the optically thick and equatorial Keplerian disk.…”

“…To maintain the energy balance condition across the boundary layer, shock propagates inward, and the post-shock boundary layer shrinks inside, reducing the corona size; however, it is restricted by the entropy gain in post-shock flows. Thus, the properties of radiative shocks have also been well investigated in the recent literature (Fukue 1982;Lu & Feng 1997;Zanotti et al 2011;Fukue 2019aFukue , 2019bMondal & Basu 2020). In addition, a number of applications have been studied in various interdisciplinary areas like computational fluid dynamics, interstellar medium, supernovae, neutron star systems, accretion disks around young star objects, plasma physics, cosmological systems, collapsing stars, gamma-ray bursts, mergers of galaxies, etc.…”