ChandraHigh‐Resolution Spectroscopy of the Absorption‐Line Features in the Low‐Mass X‐Ray Binary GX 13+1

Abstract

We present the results of high-resolution spectroscopy of absorption-line features of highly ionized ions in the X-ray spectra of GX 13+1 with the Chandra HETGS. We have resolved Kabsorption lines of hydrogen-like Fe, Mn, Cr, Ca, Ar, S, Si, and Mg ions and helium-like Fe ions. Applying the Voigt profile to these spectral features, we find that the plasma responsible for the absorption lines has a significant blueshift of 460 � 70 km s � 1 , indicating an outflow velocity of � 400 km s � 1 corrected for the proper motion, with a line-of-sight velocity dispersion of 490 þ110 � 140 km s � 1 . The plasma is photoionized with an ionization parameter of log� ' 4:1 4:7. The inferred mass outflow rate is 0:7 ; 10 18 gs � 1 or higher, comparable to the mass accretion rate (10 18 gs � 1 ) estimated from the continuum spectrum. This indicates that the mass outflow plays a significant role to determine the whole dynamics of the accretion disk. We consider a simplified radiation-driven disk wind model for the origin of the outflow. Our observations are explained by the wind originating from radii of � 10 10 -10 11 cm with a density k10 13 cm � 3 . Subject headings: stars: individual (GX 13+1) — X-rays: binaries — X-rays: stars