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A New Method to Resolve X-Ray Halos around Point Sources with Chandra Data and Its Application to Cygnus X-1With excellent angular resolution, good energy resolution, and a broad energy band, the Chandra Advanced CCD Imaging Spectrometer (ACIS) is the best instrument for studying the X-ray halos around some Galactic X-ray point sources caused by the dust scattering of X-rays in the interstellar medium. However, the direct images of bright sources obtained with the ACIS usually suffer from severe pileup. Making use of the fact that an isotropic image could be reconstructed from its projection in to any direction, we can reconstruct the images of the X-ray halos from the data obtained with the High Energy Transition Grating Spectrometer (HETGS) and/or in continuos clocking (CC) mode. These data have no or less serious pileup and enable us to take full advantage of the excellent angular resolution of Chandra. With the reconstructed high-resolution images, we can probe the X-ray halos as close as 1" to their associated point sources. Applying this method to Cygnus X-1 observed with the Chandra HETGS in CC mode, we derived an energy-dependent radial halo flux distribution and concluded that in a circular region (2' in radius) centered a the point source: (1) relative to the total intensity, the fractional halo intensity is about 15% at keV and drops to aboout 5% at approximately 6 keV (2) about 50% of the halo photons are within the region of a radius less than 40 inches and (3) the spectrum of the pooint source is slightly distorted by the halo contamination.
Document ID
20040074345
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Yao, Yangsen
(Alabama Univ. Huntsville, AL, United States)
Zhang, Shuang Nan
(Alabama Univ. Huntsville, AL, United States)
Zhang, Xiao-Ling
Feng, Yu-Xin
(Alabama Univ. Huntsville, AL, United States)
Date Acquired
August 21, 2013
Publication Date
September 1, 2003
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 594
Issue: 1
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: NAG5-7927
Distribution Limits
Public
Copyright
Other

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