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Title: Cross-calibration of the X-ray instruments onboard the Chandra, INTEGRAL, RXTE, Suzaku, Swift, and XMM-Newton observatories using G21.5-0.9
Authors: Tsujimoto, M.
Guainazzi, M.
Plucinsky, P. P.
Beardmore, A. P.
Ishida, M.
Natalucci, L.
Posson-Brown, J. L. L.
Read, A. M.
Saxton, R. D.
Shaposhnikov, N. V.
First Published: 29-Nov-2010
Publisher: EDP Sciences for European Southern Observatory (ESO)
Citation: Astronomy & Astrophysics, 2011, 525
Abstract: Context. For many years, X-ray astronomy missions have used the Crab nebula as a celestial calibration source for the X-ray flux and spectral shape. However, the object is often too bright for current and future missions equipped with instruments with improved sensitivity. Aims. We use G21.5–0.9, a pulsar-wind nebula with a time-constant power-law spectrum and a flux of a few milli-Crab in the X-ray band, as a viable, fainter substitute to the Crab. Using this source, we conduct a cross-calibration study of the instruments onboard currently active observatories: Chandra ACIS, Suzaku XIS, Swift XRT, and XMM-Newton EPIC (MOS and pn) for the soft-band, and INTEGRAL IBIS-ISGRI, RXTE PCA, and Suzaku HXD-PIN for the hard band. Methods. We extract spectra from all instruments and fit under the same astrophysical assumptions. We compare the spectral parameters of the G21.5–0.9 model: power-law photon index, H-equivalent column density of the interstellar photoelectric absorption, and flux in the soft (2–8 keV) or hard (15–50 keV) energy band. Results. We identify systematic differences in the best-fit parameter values unattributable to statistical scatter of the data alone. We interpret these differences as due to residual cross-calibration problems. The differences can be as large as 20% and 9% for the soft-band flux and power-law index, respectively, and 46% for the hard-band flux. The results are plotted and tabulated as a useful reference for future calibration and scientific studies using multiple missions.
DOI Link: 10.1051/0004-6361/201015597
ISSN: 0004-6361
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2010 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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