2002/04/30 by Randall K. Smith, R. J. Edgar, Richard J. Edgar +2 · 70 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Halo #Line (geometry) #Line-of-sight #Optics #Physics #Population #Scattering #X-ray #astro-ph
paper · pdf · doi:10.1086/344151
published in The Astrophysical Journal 581(1), 562-569 (IOP Publishing) · 19 pages, 13 figures, accepted by ApJ. New PSF calibration data used which remove uncertainties in original paper; paper substantially revised
arxiv created 2002/08/08 · openalex publication_date 2002/12/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 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.