1999/04/06 by K. Iwasawa, A. C. Fabian, K. Nandra · 3 citations
Engineering · Mathematics · Physics and Astronomy · #Calibration and Measurement Techniques #Statistical and numerical algorithms #X-ray Spectroscopy and Fluorescence Analysis #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1999.02664.x
9 pages, accepted for publication in MNRAS
arxiv created 1999/04/06 · openalex publication_date 1999/08/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report on simultaneous ASCA and ROSAT observations of the Seyfert galaxy NGC 5548 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 data sets. The photon-index obtained from the ROSAT PSPC exceeds that from the ASCA SIS ΔΓ≈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.