ASCA and ROSAT observations of NGC 5548: discrepant spectral indices
Abstract
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 DeltaGamma~0.4. The discrepancy is clear even in the 0.5-2keV 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 1999
- DOI:
- 10.1046/j.1365-8711.1999.02664.x
- arXiv:
- arXiv:astro-ph/9904071
- Bibcode:
- 1999MNRAS.307..611I
- Keywords:
-
- Astrophysics
- E-Print:
- 9 pages, accepted for publication in MNRAS