Magnetic flares and the observed τt ∼ 1 in seyfert galaxies

Sergei Nayakshin, Fulvio Melia

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


We here consider the pressure equilibrium during an intense magnetic flare above the surface of a cold accretion disk. Under the assumption that the heating source for the plasma trapped within the flaring region is an influx of energy transported inward with a group velocity close to c, e.g., by magnetohydrodynamic waves, this pressure equilibrium can constrain the Thomson optical depth, ΤT, to be of order unity. We suggest that this may be the reason why τT ∼ 1 in Seyfert galaxies. We also consider whether current data can distinguish between the spectrum produced by a single X-ray-emitting region with τT ∼ 1 and that formed by many different flares spanning a range of τT. We find that the current observations do not yet have the required energy resolution to permit such a differentiation. Thus, it is possible that the entire X-ray/γ-ray spectrum of Seyfert galaxies is produced by many independent magnetic flares with an optical depth of 0.5 < τT < 2.

Original languageEnglish (US)
Pages (from-to)L13-L16
JournalAstrophysical Journal
Issue number1 PART II
StatePublished - 1997


  • Acceleration of particles
  • Agnetic fields
  • Galaxies: Seyfert
  • Lack hole physics
  • Plasmas
  • Radiation mechanisms: nonthermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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