2002ApJ...565.1141S -
Astrophys. J., 565, 1141-1149 (2002/February-1)
The first high-resolution X-ray spectrum of Cygnus X-1: soft X-ray ionization and absorption.
SCHULZ N.S., CUI W., CANIZARES C.R., MARSHALL H.L., LEE J.C., MILLER J.M. and LEWIN W.H.G.
Abstract (from CDS):
We observed the black hole candidate Cyg X-1 for 15 ks with the High-Energy Transmission Grating Spectrometer aboard the Chandra X-Ray Observatory. The source was observed during a period of intense flaring activity, so it was about a factor of 2.5 brighter than usual, with a 0.5-10 keV (1-24 Å) luminosity of 1.6x1037 ergs.s–1 (at a distance of 2.5 kpc). The spectrum of the source shows prominent absorption edges, some of which have a complicated substructure. We use the most recent results from laboratory measurements and calculations to model the observed substructure of the edges. From the model, we derive a total absorption column of 6.21±0.22x1021 cm–2. Furthermore, the results indicate that there are ∼10%-25% abundance variations relative to solar values for neon, oxygen, and iron. The X-ray continuum is well described by a two-component model that is often adopted for black hole candidates: a soft multicolor disk component (with kT=203 eV) and a hard power-law component (with a photon index of ∼2). Comparing the fit results to those of the hard and soft states, we conclude that the source was in a transitional state. Finally, the spectrum also shows the presence of faint emission lines, which could be attributed to highly ionized species.
Abstract Copyright:
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Journal keyword(s):
Accretion, Accretion Disks - Stars: Binaries: Close - Black Hole Physics - stars: individual (Cygnus X-1) - Techniques: Spectroscopic - X-Rays: Stars
Simbad objects:
7
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