Observations of AR Sco with Chandra and AstroSat soft X-ray telescope

Abstract

We present our AstroSat soft X-ray observations of a compact binary system, AR Sco, and analysis of its X-ray observations with Chandra that were taken only about a week before the AstroSat observations. An analysis of the soft X-ray (0.3-2.0 keV) data limits the modulation of the spin, orbital, or beat periods to less than 0.03 counts s(-1) or <10% of the average count rate. The X-ray flux obtained from both observatories is found to be almost identical (within a few percent) in flux, and about 30% lower than reported from the nine months older observations with XMM- Newton. A two-temperature thermal plasma model with the same spectral parameters fit Chandra and AstroSat data very well, and requires very little absorption in the line of sight to the source. The low-temperature component has the same temperature (similar to 1 keV) as reported earlier, but the high-temperature component has a lower temperature of 5.0(-0.7)(+0.8) keV as compared to 8.0 keV measured earlier, however, the difference is not statistically significant.