A ROSAT observation of NGC 5548.
Abstract
We present a detailed spectral and temporal analysis of a long (~20 ks) ROSAT PSPC pointing centred on the bright Seyfert 1 galaxy NGC 5548. The spectrum is particularly complex, with a two-component model favoured, confirming the existence of the soil excess in this source. In addition, an absorption feature arising from highly ionized oxygen in the line of sight has been detected, consistent with an origin in the `warm absorber' which has been found to be a common feature in Seyfert galaxies observed by Ginga. The energy and depth of the feature should allow us to constrain the density and geometry of the absorbing gas, which may lie close to the central continuum source. NGC 5548 was in a low X-ray state during the observation, brightening by a factor of ~2 on a time-scale of ~2 d. Time-resolved spectral analysis shows a change in the ratio of the hard and soft fluxes, consistent with reprocessing models.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1993
- DOI:
- 10.1093/mnras/260.3.504
- Bibcode:
- 1993MNRAS.260..504N
- Keywords:
-
- Rosat Mission;
- Seyfert Galaxies;
- X Ray Astronomy;
- Light Curve;
- Spectrum Analysis;
- X Ray Spectra;
- Astrophysics