Constraints on the inner accretion flow of 4U /MXB 1636-53 (V 801 Arae) from a comparison of X-ray burst and persistent emission.
van Paradijs, J.; Wijers, R. A. M. J.; Lewin, W. H. G.; Jansen, F.; Oosterbroek, T.; Penninx, W.; Damen, E.
Netherlands
Abstract
A detailed analysis is presented of the importance of Comptonization in burst and persistent spectra of the low-mass X-ray binary 4U/MXB 1636-53, and from this analysis it is inferred that the inner accretion flow is geometrically thin. It is found that burst spectra of 1636-53 are very nearly Planckian in shape; from an upper limit to a high-energy excess in these spectra it is inferred that the Thomson scattering optical depth of a possible intervening hot cloud must be less than 1 during bursts, and that the Compton y parameter of that cloud must be less than 0.5. During persistent emission, Thomson optical depth of 4-8, an electron temperature of 2-5 keV, and a value of 0.8-1.1 for y are inferred.