Probing the inner regions around accreting black holes
Abstract
Accretion of matter onto compact objects such as black holes (BHs) displays a common phenomenology based on the fact that the physical processes acting on these systems are the same and appear to scale with the mass of the BH, covering a wide range of values from stellar-mass (e.g. black hole binaries; BHBs) to supermassive (e.g., active galactic nuclei; AGN). Most of this phenomenology is observed in the X-ray band, including relativistic and ionized reflection, reverberation time lags, and quasi period oscillations (QPOs). Here we discuss several controversial results derived from our analysis of the observational data for several accreting BHs. In particular, the physical origin of the hard X-ray continuum in accreting black holes is still unknown, as it can be explained by either a Comptonizing gas of hot electrons (the "corona") or the base of a relativistic jet. The geometry and properties of this central source of X-rays are still a mystery. In BHBs, the truncation of the accretion disk is also a controversial subject, with predictions that differ by orders of magnitude when reflection spectroscopy and/or timing techniques are implemented. Another unexpected result is the questionably large abundance of iron required by most reflection models to explain the observable data from both BHB and AGN alike. The strong correlations among these and other important parameters pose serious limitations on the understanding of accreting sources. We present concrete efforts in answering these questions for several emblematic BHBs and AGNs, with particular emphasis on the advances and limitations of current models for ionized X-ray reflection in strong gravitational fields.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1167G