ASTROSAT-LAXPC observations of MAXI transient sources

摘要

ASTROSAT is an astronomy satellite being made for a launch in 2009. It is designed for simultaneous multi-wavelength studies with five payloads in the optical/UV and a broad X-ray energy range. One of the instruments, a set of three large area xenon proportional counters (LAXPC) will enable high time resolution X-ray measurements in the 2-80 keV band with moderate energy resolution. There are two imaging X-ray spectrometers, one in the soft and one in the hard X-ray band. Two telescopes will provide multi-band imaging in three optical/UV channels. An X-ray sky monitor onboard ASTROSAT, that is similar in concept to the RXTE-ASM will be used to study long term intensity variations of bright X-ray sources. This instrument will also facilitate timely X-ray observations of transient and variable sources with the LAXPC and other payloads. Here we discuss the salient features of the LAXPC and its advantage of previous large area X-ray astronomy instruments. A very large effective area for hard X-rays with good energy resolution will allow the LAXPC to probe certain properties of X-ray sources with unprecedented detail. The main science issues to be addressed with the LAXPCs are discussed here with some simulated results. We particularly mention the science topics related to variable and transient X-ray sources for which the ASTROSAT observations will benefit from the all sky monitoring with MAXI.