Related papers: Results from AstroSat LAXPC Observations of Hercul…
Hercules X-1/HZ Hercules (Her X-1/HZ Her) is an X-ray binary monitored by multiple X-ray missions since last century. With the abundance of long-term observations, we present a complete set of orbital light-curves of Her X-1/HZ Her during…
Her X-1 has been monitored nearly continuously in soft X-rays (2-12 keV) since February 1996 by the ASM on board RXTE. We present analysis of these observations which include 23 contiguous 35-day cycles. We present the best yet average…
We present results of a 5.7 day duration BeppoSAX observation of the short-on state of Her X-1 and a short observation during the decline of the preceding main-on state. The 0.1-10 keV spectra can be fit with a power-law and blackbody model…
Hercules X-1 is a nearly edge-on X-ray binary with a warped, precessing accretion disk, which manifests through a 35-day cycle of alternating High and Low flux states. This disk precession introduces a changing line of sight towards the…
Swift/BAT and RXTE/ASM observations have monitored the X-ray binary system Her X-1 for approximately 14.5 years each, and both were monitoring Her X-1 for a period of ~5.5 years. Here we study the 35-day cycle using these observations.…
Results of a 1999 July 8-10 BeppoSAX observation during an anomalous low-state of Her X-1 are presented. The standard on-state power-law and blackbody continuum model is excluded at high confidence unless partial covering is included. This…
We report on the timing analysis of the observation of the X-ray binary pulsar Her X-1 performed during the BeppoSAX Science Verification Phase. The observation covered more that two full orbital cycles near the maximum of the main-on in…
We present a broad-band X-ray timing study of the variations in pulse behavior with superorbital cycle in the low-mass X-ray binary Her X-1. This source shows a 35-day superorbital modulation in X-ray flux that is likely caused by…
We report the first analysis of data from AstroSat/LAXPC observations of Cygnus X-1 in January 2016. LAXPC spectra reveals that the source was in the canonical hard state, represented by a prominent thermal Comptonization component having a…
RXTE ASM count rates from the X-ray pulsar Her X-1 began falling consistently during the late months of 2003. The source is undergoing another state transition similar to the anomalous low state of 1999. This new event has triggered…
Results of a BeppoSAX observation of Her X-1 in 2000 October during the first main-on state after the longest recorded anomalous low-state are presented. The 0.1-30 keV spectrum, light curve and pulse profile are all consistent with those…
We present an improved background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on-board AstroSat. Because of the large collecting area and high pressure, the LAXPC instrument has a large background count rate, which…
The X-ray binary Her X-1 consists of an accreting neutron star and the optical component HZ Her. The 35-day X-ray superorbital variability of this system is known since its discovery in 1972 by the Uhuru satellite and is believed to be…
We present RXTE monitoring of the eclipsing X-ray binary Hercules X-1 conducted over the short-high state of July 1998. This was one of the last major short-high states before the source entered an anomalous low-state of activity. A…
Analysis and interpretation of the Her X-1 X-ray light curve obtained with the ASM onbord RXTE over the period 1996 February to 2004 September is presented. We report that the features found previously in the averaged X-ray lightcurve are…
We analyse RXTE/PCA X-ray spectra of the binary X-ray pulsar Her X-1/HZ Her during short high state and one binary orbit in the preceding low state, just before short high turn-on. The spectrum is well described by two continuum components…
We present the results of a series of XMM-Newton EPIC and OM observations of Her X-1, spread over a wide range of the 35 day precession period. We confirm that the spin modulation of the neutron star is weak or absent in the low state - in…
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…
The study of fast variability properties in X-ray binaries advances our understanding of the physical processes and geometric properties of the accretion flow around the compact object. In this work, we study the evolution of the timing…
A failed main-on in the 35d cycle of Her X-1 was observed with the Rossi X-Ray Timing Explorer (RXTE) on 1999 April 26. Exceptions to the normal 35d cycle have been seen only twice before; in 1983 and again 1993. We present timing and…