2016/04/20 by Sandip K. Chakrabarti, Chakrabarti, Sandip K. · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.1604.05955
openalex publication_date 2016/04/20 · openalex created_date 2022/10/04 · openalex updated_date 2026/07/28
An accretion flow around a black hole has a saddle type sonic point just\noutside the event horizon to guarantee that the flow enters the black hole\nsupersonically. This feature exclusively present in strong gravity limit makes\nits marks in every observation of black hole candidates. Another physical sonic\npoint is present (as in a Bondi flow) even in weak gravity. Every aspect of\nspectral or temporal properties of every black hole can be understood using\nthis transonic or advective flow having more than one saddle type points. This\nmost well known and generalized solution with viscosity and radiative transfer\nhas been verified by numerical simulations also. Spectra, computed for various\ncombinations of the standard Keplerian, and advective sub-Keplerian components\nmatch accurately with those from satellite observations. Standing, oscillating\nand propagatory oscillating shocks are produced due to centrifugal barrier of\nthe advective component. The post-shock region acts as the Compton cloud\nproducing the power-law spectra. Jets and outflows are also produced from this\npost-shock region, commonly known as the CENtrifugal barrier supported BOundary\nLayer or CENBOL. In soft states, the CENBOL is cooled down by soft photons from\nthe Keplerian disk, and thus the outflow is absent. Type-C and Type-B QPOs are\ngenerated respectively due to strong and weak resonance oscillations of the\nCENBOL. Away from resonance, oscillation may be triggered when Rankine-Hugoniot\nconditions are not satisfied and Type-A QPOs could be seen.\n