2006/06/26 by Thomas W. J. Thompson, Richard E. Rothschild, John A. Tomsick
Physics and Astronomy · #Angular diameter #Astrophysical Phenomena and Observations #Brightness #Distance modulus #Galaxy #Gamma-ray bursts and supernovae #Halo #Light curve #Observational error #Optical depth #Point spread function #Pulsars and Gravitational Waves Research #Surface brightness #astro-ph
paper · pdf · doi:10.1086/507173
published as Astrophys.J.650:1063-1069,2006 · 7 pages, 4 figures; Accepted for publication in ApJ
arxiv created 2006/06/26 · openalex publication_date 2006/10/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
With the excellent angular resolution of the Chandra X-Ray Observatory , it is possible to geometrically determine the distance to variable Galactic sources, based on the phenomenon that scattered radiation appearing in the X-ray halo has to travel along a slightly longer path than the direct, unscattered radiation. By measuring the delayed variability, constraints on the source distance can be obtained if the halo brightness is large enough to dominate the point-spread function (PSF) and to provide sufficient statistics. The distance to Cyg X-3, which has a quasi-sinusoidal light curve, has been obtained with this approach by Predehl et al. Here we examine the feasibility of using the delayed signature of type I X-ray bursts as distance indicators. We use simulations of delayed X-ray burst light curves in the halo to find that the optimal annular region and energy band for a distance measurement with a grating observation are roughly 10''-50'' and 1-5 keV, respectively, assuming Chandra 's effective area and PSF, uniformly distributed dust, the input spectrum and optical depth to GX 13+1, and the Weingartner & Draine interstellar grain model. We find that the statistics are dominated by Poisson noise rather than systematic uncertainties, such as the PSF contribution to the halo. Using Chandra , a distance measurement to such a source at 4 (8) kpc could be made to about 23% (30%) accuracy with a single burst with 68% confidence. By stacking many bursts, a reasonable estimate of systematic errors limits the distance measurement to about 10% accuracy.