High-Resolution X-Ray Spectroscopy of the Accretion Disk Corona Source 4U 1822−37

Abstract

We present a preliminary analysis of the X-ray spectrum of the accretion disk corona source 4U 1822-37 obtained with the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory. We detect discrete emission lines from photoionized iron, silicon, magnesium, neon, and oxygen as well as a bright iron fluorescent line. Phase-resolved spectroscopy suggests that the recombination emission comes from an X-ray-illuminated bulge located at the predicted point of impact between the disk and the accretion stream. The fluorescent emission originates in an extended region on the disk that is illuminated by light scattered from the corona.