Highly Ionized Absorption in the X-ray Spectrum of Cyg X-1

Abstract

Using the Chandra High Energy Transmission Grating Spectrometer (HETGS), we have found significant absorption features in the X-ray spectrum of Cyg X-1 taken in the continuous clocking mode. These features include resonance lines of He-like ions of S, Si, and Mg; the Ly alpha lines of H-like S, Si, Mg, and Ne; and several lower ionization lines of Fe XX, XXII, and XXIV. Preliminary analysis shows that the lines are resolved in many cases, giving line widths of order 300 km/s and are redshifted by 460 +/- 10 km/s. These features are interpreted in the context of an accreting stellar wind model that is ionized by the X-ray source. In addition, there are clear absorption features due to neutral Mg, Fe, and O in the interstellar medium.

4 pages, 3 figures, in X-ray Emission from Accretion onto Black Holes, Proceedings of a joint workshop held by the Center for Astrophysics (Johns Hopkins University) and the Laboratory for High Energy Astrophysics (NASA/Goddard Space Flight Center) in Baltimore, MD, June 20-23, 2001, Eds.: T. Yaqoob and J.H. Krolik, published electronically, E45