2011/06/17 by R. D. Saxton, A. Read, Saxton, Richard +7
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.1106.3507
openalex publication_date 2011/06/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 ∼ 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.