A ROSAT observation of NGC 5548

K. Nandra, A. C. Fabian, I. M. George, G. Branduardi-Raymont, A. Lawrence, K. O. Mason, I. M. McHardy, K. A. Pounds, G. C. Stewart, M. J. Ward, R. S. Warwick

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We present a detailed spectral and temporal analysis of a long ROSAT PSPC pointing centered on the bright Seyfert 1 galaxy NGC 5548. The spectrum is particularly complex, with a two-component model favored, confirming the existence of the soft 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 about 2 on a time-scale of about 2 d. Time-resolved spectral analysis shows a change in the ratio of the hard and soft fluxes, consistent with reprocessing models.
Original languageEnglish
Pages (from-to)504-512
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 1 Feb 1993

Keywords / Materials (for Non-textual outputs)

  • Rosat Mission
  • Seyfert Galaxies
  • X Ray Astronomy
  • Light Curve
  • Spectrum Analysis
  • X Ray Spectra


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