We present an improved background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on-board AstroSat. Because of large collecting area and high pressure, LAXPC instrument has a count rate, which varies during orbit. Apart from variation with latitude longitude orbit there is prominent quasi-diurnal not been modelled earlier. Using over 5 years observations, we determined pe...

We present the time variability characteristics of Cygnus X-1 in its two spectral states. The observations were carried out using the Pointed Proportional Counters (PPC) onboard the IndianX-rayAstronomyExperiment (IXAE). The details of the instrument characteristics, the observation strategy, and the backgroundmodelingmethods are described. In the soft state ofCygX-1,we confirm the general tren...

National Bureau of Standards Gaithersburg, MD 20899 Two alpha-particle counting systems for the measurement of large-area sources have been developed at the National Bureau of Standards. The systems and their characteristics are described. One system uses an internal-source proportional counter and the other measures sources external to the counting volume through a thin aluminized mylar window...