18 July 2000 Low-energy effective area of the Chandra low-energy transmission grating spectrometer
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The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present preliminary results from in- flight calibration of the low energy response of the High Resolution Camera Spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrometer (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (Teff equals 25000 K and log g equals 9.0) for comparison with the Chandra observations of Sirius B. Pre-flight calibration of the LETGS effective area was conducted only at wavelengths shortward of 45 angstroms (E > 0.277 keV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths overestimates the effective area on average by a factor of 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 45 - 185 angstroms. We make an independent test of our results by comparing a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.
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Deron O. Pease, Jeremy J. Drake, C. Olivia Johnson, Vinay L. Kashyap, Ralph Porter Kraft, Peter W. Ratzlaff, Bradford J. Wargelin, A. C. Brinkman, Jelle S. Kaastra, Rob van der Meer, Frits B. S. Paerels, Vadim Burwitz, Peter Predehl, Herman L. Marshall, Martin Adrian Barstow, D. S. Finley, Jean Dupuis, "Low-energy effective area of the Chandra low-energy transmission grating spectrometer", Proc. SPIE 4012, X-Ray Optics, Instruments, and Missions III, (18 July 2000); doi: 10.1117/12.391609; https://doi.org/10.1117/12.391609


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