Long-term AGN variability and the case of GSN 069

Abstract

We report on a study of long-term flux variations in a sample of more than 1000 AGN observed with ROSAT and in the XMM-Newton slew survey. Over a period of 3-19 years, NLS1 galaxies as a class are found to be only slightly more variable than broad line Seyfert galaxies, despite the strong short term variability seen in some bright nearby NLS1s. Contrary to expectations, it is Seyfert II galaxies that exhibit the greatest flux volatility. One particular Sy II, which has brightened by a factor > 300 over 15 years, has been monitored in detail with Swift and XMM. The spectrum is extremely soft (kT \sim 60eV) consistent with pure thermal emission from an accretion disk and reminiscent of ROSAT observations of the NLS1,WPVS 007. We show that this is likely to be a "true" Sy II, without a BLR, and speculate that in its new high luminosity state we may be able to witness a BLR in formation.

arXiv commentTo be pulished in the conference proceedings 'Narrow-Line Seyfert 1 Galaxies and Their Place in the Universe' - 13 pages, 8 figures; http://nls1.brera.inaf.it/

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• A high Eddington-ratio, true Seyfert 2 galaxy candidate: implications for broad-line-region models
• Characterisation of AGN from the XMM-Newton Slew Survey