Authors

G. Pszota
W. Cui

Published in:

Astrophysical Journal 663,2 (2007) 1201-1206;

Abstract

We critically examine issues associated with determining the fundamental properties of the black hole and the surrounding accretion disk in an X-ray binary based on modeling the disk X-ray continuum of the source. We base our work mainly on two XMM-Newton observations of GX 339-4, because they provided high-quality data at low energies ( below 1 keV), which are critical for reliably modeling the spectrum of the accretion disk. A key issue examined is the determination of the so-called "color correction factor,'' which is often empirically introduced to account for the deviation of the local disk spectrum from a blackbody ( due to electron scattering). This factor cannot be predetermined theoretically, because it may vary with, e. g., mass accretion rate, among a number of important factors. We follow up on an earlier suggestion to estimate the color correction observationally by modeling the disk spectrum with saturated Compton scattering. We show that the spectra can be fitted well, and the approach yields reasonable values for the color correction factor. For comparison, we have also attempted to fit the spectra with other models. We show that even the high-soft state continuum ( which is dominated by the disk emission) cannot be satisfactorily fitted by state-of-the-art disk models. We discuss the implications of these results.

Keywords

accretion, accretion disks;; black hole physics;; stars : individual (GX;; 339-4);; X-rays : stars;; Astronomy & Astrophysics

Date of this Version

January 2007

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.