2004ApJ...609..325U

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 Kα absorption 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, indicating an outflow velocity of ~400 km/s corrected for the proper motion, with a line-of-sight velocity dispersion of 490⁺¹¹⁰_–140 km/s. The plasma is photoionized with an ionization parameter of logξ≃4.1-4.7. The inferred mass outflow rate is 0.7x10¹⁸ g/s or higher, comparable to the mass accretion rate (10¹⁸ g/s) 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 ∼10¹⁰-10¹¹ cm with a density ≳10¹³/cm3.