Quasi-periodic oscillations in X-ray emission from the Seyfert galaxy NGC5548

I. E. Papadakis, A. Lawrence

Research output: Contribution to journalArticlepeer-review


Archival Exosat observations of the bright Seyfert galaxy NGC5548 are analyzed, and a broad peak is found in the power spectrum which corresponds to quasi-periodic oscillations (QPOs) with a period of about 500 s. Both the frequency and the magnitude of the QPOs vary systematically with total X-ray luminosity. Similar behavior has been seen in compact Galactic X-ray binaries, and it is suggested that intensity-correlated QPOs may be a generic feature of accretion onto a compact object. If the QPOs in the NGC5548 derive from instability or variability in an accretion disk around a black hole, the black hole mass can be only a few hundred thousand solar masses, an uncomfortably small number for most AGN models.
Original languageEnglish
Pages (from-to)233-236
Publication statusPublished - 1 Jan 1993


  • Active Galactic Nuclei
  • Cosmic X Rays
  • Galactic Radiation
  • Oscillations
  • Seyfert Galaxies
  • Noise Spectra
  • Power Spectra


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