RXTE highlights of 34.85-day cycle of Her X-1

An analysis of the publically available RXTE archive on Her X-1 including data on 23 34.85-day cycles is performed. The turn-on times for these cycles are determined. The number of cycles with a duration of 20.5 orbits has been found exceedingly larger than of shorter (20 orbits) or longer (21 orbits). A correlation between the duration of a cycle and its mean X-ray flux is noted. The mean X-ray light curve shows a very distinct short-on state. The anomalous X-ray absorption dip is found during the first orbit after the turn-on in the main-on state for the cycles starting near the binary phase 0.25, while is present during two successive orbits in the low-on state. The post-eclipse recovery feature have not been found in the main-on state but appears at least for two orbits during the low-on state. The pre-eclipse dips are present both in main-on and low-on state and demonstrate the behaviour as in early observations. The comparison of durations of the main-on and short-on states enabled us to constrain the accretion disk semi-thickness and its inclination to the orbital plane.Comment: 7 pages with 4 eps figures (large figures 1, 4a,b, 5a,b are available at ftp://xray.sai.msu.su/pub/preprints/Prokhorov/rxte/ or at ftp://xray.sai.msu.ru/pub/preprints/Prokhorov/rxte/), LaTeX, uses mn.sty. Submitted to MNRA

Modeling of non-stationary accretion disks in X-ray novae A 0620-00 and GRS 1124-68 during outburst

We address the task of modeling soft X-ray and optical light curves of X-ray novae in the high/soft state. The analytic model of viscous evolution of an externally truncated accretion \alpha-disk is used. Relativistic effects near a Kerr black hole and self-irradiation of an accretion disk are taken into account. The model is applied to the outbursts of X-ray nova Monocerotis 1975 (A 0620-00) and X-ray nova Muscae 1991 (GRS 1124-68). Comparison of observational data with the model yields constraints on the angular momentum (the Kerr parameter) of the black holes in A 0620-00 and GRS 1124-68: 0.3-0.6 and \leq 0.4, and on the viscosity parameter \alpha of the disks: 0.7-0.95 and 0.55-0.75. We also conclude that the accretion disks should have an effective geometrical thickness 1.5-2 times greater than the theoretical value of the distance between the photometric layers.Comment: 12 pages, 11 figures, 1 table, accepted for publication in A&A (minor changens following the referee's comments, five references added