The ongoing transformation of Seyfert galaxy 1ES 1927+654
Abstract
In March 2018, the transient ASASSN-18el occurred in the nucleus of Seyfert 2 galaxy 1ES1927+654. Monitoring the source over several months our team discovered the emergence of broad Balmer emission lines, suggesting a transition from Type 2 to a Type 1 AGN on timescales consistent with the light travel time between the central black hole and the broad line region. Archival X-ray and optical observations of 1ES1927+654 in 2011 already showed an interesting AGN, which, while optically classified as a Type-2, showed an X-ray spectrum typical of an unobscured Type 1 AGN. After the recent optical outburst, the X-ray spectrum changed dramatically, with the hard X-ray corona decreasing by >2 orders of magnitude, and instead now resembles a 10^6 K thermal spectrum. In this talk, I will give an overview of our ongoing multi-wavelength follow-up with NICER, HST, XMM-Newton, NuSTAR, Keck, Swift and Las Cumbres Observatory of this unprecedented changing-look AGN. I discuss potential reasons for the onset of this accretion activity, including the tantalizing possibility that we observed the tidal disruption of a star that caused an instability in the pre-existing AGN disc and corona.
- Publication:
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AAS/High Energy Astrophysics Division
- Pub Date:
- March 2019
- Bibcode:
- 2019HEAD...1710101K