Abstract
We present active galactic nuclei (AGNs) that have shown extreme amplitude variability in X-rays. These AGN appear as bright for long periods, but then suddenly become extremely X-ray weak sources. Most likely this behavior is due to strong absorption along the line of sight or by relativistically blurred reflection. Two extreme examples are the Narrow Line Seyfert 1 (NLS1) galaxies WPVS 007 and Mkn 335. WPVS 007 is a peculiar AGN because it combines the properties of a normal NLS1 with those of a broad-absorption line (BAL) quasar, which typically only appear in high-luminousity, high black hole mass systems. Mkn 335 has appeared an an X-ray bright AGN for most of the past few decades, but was caught by Swift in a deep X-ray flux minimum state in 2007, and has remained in that state for most of the time since. One potential explanation for this low state is absorption. Several Other AGN have been in deep minimum X-ray flux states, including PG 0844+349 and 1H 0707–495, for which the dramatic drops in X-ray flux have been explained by blurred X-ray reflection.
Highlights
WPVS 007 is a peculiar AGN because it combines the properties of a normal Narrow Line Seyfert 1 (NLS1) with those of a broad-absorption line (BAL) quasar, which typically only appear in high-luminousity, high black hole mass systems
The highest amplitudes of X-ray variability ever observed, have been from otherwise inactive galaxies, and these represent the best candidates to date for stellar tidal disruption events (TDEs)
A successful way to discover X-ray variability is through X-ray surveys, like the ROSAT All-Sky Survey (RASS)
Summary
The highest amplitudes of X-ray variability ever observed (factors >1000–6000), have been from otherwise inactive galaxies, and these represent the best candidates to date for stellar tidal disruption events (TDEs). In addition to IC 3599 [2, 14, 27], there are three more sources in that sample which display dramatic decreases in their ROSAT PSPC counts rates: WPVS 007, RX J2217.9–5941, and RX J1624.9+7554 ([15, 18], and [16], respectively). The latter is an inactive galaxy and our interpretation of the X-ray outburst in this source was a TDE, similar to other ROSAT-discovered sources like NGC 5905 (e.g., [27]).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
