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ASCA and ROSAT observations of NGC5548: discrepant spectral indices

K. Iwasawa·A. C. Fabian·K. Nandra
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Abstract

We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC5548 made during the ASCA Performance Verification phase. Spectral features due to a warm absorber and reflection are clearly seen in the X-ray spectra. We find that the continuum spectral shape differs between the ASCA and ROSAT datasets. The photon-index obtained from the ROSAT PSPC exceeds that from the ASCA SIS about 0.4. The discrepancy is clear even in the 0.5-2 keV energy band over which both detectors are sensitive. The spectra cannot be made consistent by choosing a more complex model. The problem likely lies in the response curve (estimated effective area) of one, or both, detectors. There may be important consequences for a wide range of published results.

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K. Iwasawa, A. C. Fabian, K. Nandra. 1999-04-06. ASCA and ROSAT observations of NGC5548: discrepant spectral indices. https://doi.org/10.1046/j.1365-8711.1999.02664.x

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