Disk-corona interactions in soft spectral states of black hole binaries

Abstract

Re-analysis of some archival X-ray data of black hole binaries in soft spectral states is presented. Results of detailed spectral fitting, including proper physical description of the X-ray reprocessed component, indicate that in most cases the soft, thermal disk emission cannot be described by a simple multi-color blackbody model. Additional Comptonization of those seed photons provides an acceptable description of the soft component, implying a presence of a warm (kT~1 keV), mildly optically thick (tau~10) phase of accreting plasma. Combined spectral/temporal analysis of GS 1124-68 during 'flip-flop' transitions in Very High State suggests that the optically thick accretion flow can proceed in (at least) two modes giving the same time-integrated behaviour (i.e. energy spectra) but very different timing behaviour.