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Proceedings Paper

In-flight effective area calibration of the Chandra low-energy transmission grating spectrometer
Author(s): Deron O. Pease; Jeremy J. Drake; Vinay L. Kashyap; Herman L. Marshall; Erica L. Raffauf; Peter W. Ratzlaff; Bradford J. Wargelin
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Paper Abstract

We present the in-flight effective area calibration of the Low Energy Transmission Grating Spectrometer (LETGS), which comprises the High Resolution Camera Spectroscopic readout (HRC-S) and the Low Energy Transmission Grating (LETG) aboard the Chandra X-ray Observatory. Previous studies of the LETGS effective area calibration have focused on specific energy regimes: 1) the low-energy calibration for which we compared observations of Sirius B and HZ 43 with pure hydrogen non-LTE white dwarf emission models; and 2) the mid-energy calibration for which we compared observations of the active galactic nuclei PKS 2155-304 and 3C 273 with simple power-law models of their seemingly featureless continua. The residuals of the model comparisons were taken to be true residuals in the HRC-S quantum efficiency (QE) model. Additional in-flight observations of celestial sources with well-understood X-ray spectra have served to verify and fine-tune the calibration. Thus, from these studies we have derived corrections to the HRC-S QE to match the predicted and observed spectra over the full practical energy range of the LETGS. Furthermore, from pre-flight laboratory flatfield data we have constructed an HRC-S quantum efficiency uniformity (QEU) model. Application of the QEU to our semi-empirical in-flight HRC-S QE has resulted in an improved HRC-S on-axis QE. Implementation of the HRC-S QEU with the on-axis QE now allows for the computation of effective area for any reasonable Chandra/LETGS pointing.

Paper Details

Date Published: 11 March 2003
PDF: 12 pages
Proc. SPIE 4851, X-Ray and Gamma-Ray Telescopes and Instruments for Astronomy, (11 March 2003); doi: 10.1117/12.461275
Show Author Affiliations
Deron O. Pease, Smithsonian Astrophysical Observatory (United States)
Jeremy J. Drake, Smithsonian Astrophysical Observatory (United States)
Vinay L. Kashyap, Smithsonian Astrophysical Observatory (United States)
Herman L. Marshall, Massachusetts Institute of Technology (United States)
Erica L. Raffauf, Smithsonian Astrophysical Observatory (United States)
Peter W. Ratzlaff, Smithsonian Astrophysical Observatory (United States)
Bradford J. Wargelin, Smithsonian Astrophysical Observatory (United States)

Published in SPIE Proceedings Vol. 4851:
X-Ray and Gamma-Ray Telescopes and Instruments for Astronomy
Joachim E. Truemper; Harvey D. Tananbaum, Editor(s)

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