Signatures of strong-field gravity accretion: Relativistic~effects in spectra and polarization from black-hole accretion discs
Vladimir Karas (Astronomical Institute of the Czech Academy of Sciences, Prague)
Abstract: Theorem states states that stationary, isolated black holes can be fully characterized by a small number of parameters, however, cosmic black holes are not isolated. Instead, they interact with their gaseous and stellar environment, and so the astrophysically realistic models require many more parameters to describe the emitted light from black hole accretion disks. Variability patterns observed in light curves, as well as theoretical models of accretion flows suggest that accretion disks tend to be inhomogeneous. We will review a fruitful approach to study variety of radiation signatures from accretion disks in strong gravity. Transfer functions can be introduced, pre-computed, and then employed to generate model spectra and to fit them to the electromagnetic signal in X-rays. We have been developing this method to analyse spectra and light curves and to predict the polarimetric properties to be observed with the upcoming missions IXPE and eXTP.