The Ionized Stellar Wind in Vela X-1 during Eclipse

We present a first analysis of a high-resolution X-ray spectrum of the ionized stellar wind of Vela X-1 during eclipse. The data were obtained with the High-Energy Transmission Grating Spectrometer on board the Chandra X-Ray Observatory. The spectrum is resolved into emission lines with fluxes between 0.02 and 1.04 × 10-4 photons cm-2 s-1. We identify lines from a variety of charge states, including fluorescent lines from cold material and a warm photoionized wind. We can exclude signatures from collisionally ionized plasmas. For the first time, we identify fluorescent lines from L-shell ions from lower Z elements. We also detect radiative recombination continua from a kT = 10 eV (1.2 × 105 K) photoionized optically thin gas. The fluorescent line fluxes imly the existence of optically thick and clumped matter within or outside the warm photoionized plasma.

[1]  Ian R. Stevens,et al.  Ionization effects in the radiative driving of stellar winds in massive X-ray binary systems. , 1989 .

[2]  L. House.  Theoretical Wavelengths for Ka-TYPE X-Ray Lines in the Spectra of Ionized Atoms (carbon to Copper) , 1969 .

[3]  R. McCray,et al.  X-ray sources in stellar winds , 1977 .

[4]  W. Brandt,et al.  X-ray reflection in Galactic black hold candidates: smeared edge profiles and resonant Auger destruction , 1995, astro-ph/9510022.

[5]  Y. Kondo,et al.  Ultraviolet spectroscopic observations of HD 77581 (Vela X-1 = 4U 0900-40) , 1985 .

[6]  H. Gursky,et al.  Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source Vela X-1 /HD 77581/ , 1980 .

[7]  D. A. Verner,et al.  Atomic data for astrophysics. II. New analytic fits for photoionization cross sections of atoms and ions , 1996 .

[8]  G. Rybicki,et al.  Time-dependent models of radiatively driven stellar winds. I - Nonlinear evolution of instabilities for a pure absorption model , 1988 .

[9]  R. Brucato,et al.  Optical candidates for two X-ray sources. , 1972 .

[10]  N. White,et al.  Accretion powered X-ray pulsars , 1983 .

[11]  S. Kahn,et al.  High resolution X-ray spectroscopy of $\zeta$ Puppis with the XMM-Newton reflection grating spectrometer , 2000, astro-ph/0011026.

[12]  F. Paerels,et al.  ASCA Observations of the Magnetic Cataclysmic Variable BY Camelopardalis , 1996 .

[13]  R. Giacconi,et al.  Uhuru observations of the binary x-ray source 2U 0900-40 , 1973 .

[14]  John I. Castor,et al.  Radiation-driven winds in Of stars. , 1975 .

[15]  The X-Ray Photoionized Wind in Cen X-3/V779 Cen , 2000, astro-ph/0009257.

[16]  Delphine Porquet,et al.  X-ray photoionized plasma diagnostics with Helium-like ions. Application to Warm Absorber-Emitter in Active Galactic Nuclei , 2000 .

[17]  G. Zylstra,et al.  Line-dominated eclipse spectrum of VELA X-1 , 1994 .

[18]  Duane A. Liedahl,et al.  Photoionization-Driven X-Ray Line Emission in Cygnus X-3 , 1996 .

[19]  Duane A. Liedahl,et al.  The X-ray Spectrum and Global Structure of the Stellar Wind in VELA X-1 , 1999 .

[20]  J. Schmitt,et al.  (Erratum) The ROSAT all-sky survey catalogue of optically bright OB-type stars. , 1996 .

[21]  D. Liedahl,et al.  Collisional Plasma Models with APEC/APED: Emission-Line Diagnostics of Hydrogen-like and Helium-like Ions , 2001, astro-ph/0106478.

[22]  F. R. Harnden,et al.  The Einstein X-ray Observatory Catalog of O-type stars , 1989 .