Open AccessA complete relativistic ionized accretion disc in Cygnus X‐1
Author(s) -
Young A.J.,
Fabian A.C.,
Ross R.R.,
Tanaka Y.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04498.x
Subject(s) - physics , astrophysics , accretion (finance) , black body radiation , black hole (networking) , schwarzschild radius , astronomy , ionization , active galactic nucleus , x ray binary , relativistic quantum chemistry , neutron star , galaxy , radiation , ion , computer network , routing protocol , routing (electronic design automation) , quantum mechanics , computer science , link state routing protocol , nuclear physics
The galactic black hole candidate Cygnus X‐1 is observed to be in one of two X‐ray spectral states: either the low/hard (low soft X‐ray flux and a flat power‐law tail) or high/soft (high blackbody‐like soft X‐ray flux and a steep power‐law tail) state. The physical origin of these two states is unclear. We present here a model of an ionized accretion disc, the spectrum of which is blurred by relativistic effects, and fit it to the ASCA , Ginga and EXOSAT data of Cygnus X‐1 in both spectral states. We confirm that relativistic blurring provides a much better fit to the low/hard state data and, contrary to some previous results, find the data of both states to be consistent with an ionized thin accretion disc with a reflected fraction of unity extending to the innermost stable circular orbit around the black hole. Our model is an alternative to those that, in the low/hard state, require the accretion disc to be truncated at a few tens of Schwarzschild radii, within which there is a Thomson‐thin, hot accretion flow. We suggest a mechanism that may cause the changes in spectral state.