The X-Ray Halo of GX 13+1
Abstract
We present observations of the X-ray halo around the low-mass X-ray binary GX 13+1 from the Chandra X-ray telescope. The halo is caused by scattering in interstellar dust grains, and we use it to diagnose the line-of-sight position, size distribution, and density of the grains. Using the intrinsic energy resolution of Chandra's ACIS CCDs and the recent calibration observation of the Chandra point-spread function, we were able to extract the halo fraction as a function of energy and off-axis angle. We define a new quantity, the ``halo coefficient,'' or the total halo intensity relative to the source extrapolated to 1 keV, and measure it to be 1.5+0.5-0.1 for GX 13+1. We find a relationship between this value and the dust size, density, and hydrogen column density along the line of sight to GX 13+1. We also conclude that our data do not agree with ``fluffy'' dust models that earlier X-ray halo observations have supported and that models including an additional large dust grain population are not supported by these data.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2002
- DOI:
- 10.1086/344151
- arXiv:
- arXiv:astro-ph/0204267
- Bibcode:
- 2002ApJ...581..562S
- Keywords:
-
- ISM: Dust;
- Extinction;
- Scattering;
- X-Rays: Binaries;
- X-Rays: ISM;
- Astrophysics
- E-Print:
- 19 pages, 13 figures, accepted by ApJ. New PSF calibration data used which remove uncertainties in original paper