Magnetic flux inversion in a peculiar changing look AGN. Issue 1 (9th January 2021)

• Record Type: Journal Article
• Authors: Scepi, Nicolas; Begelman, Mitchell C; Dexter, Jason
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 502:Issue 1(2021)
• Page Start: L50
• Page End: L54
• Publication Date: 2021-01-09
• Subjects: accretion, accretion discs -- magnetic fields -- galaxies: active; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slab002
• Languages: English
• ISSNs: 1745-3933

Abstract

ABSTRACT: We argue that the changing-look event in the active galactic nucleus (AGN) 1ES 1927+654, followed by a dip of three orders of magnitude in the X-ray luminosity, is controlled by a change in the accretion rate and an inversion of magnetic flux in a magnetically arrested disc (MAD). Before the changing-look event, strong magnetic flux on the black hole powers X-ray emission via the Blandford–Znajek process, while the UV emission is produced by a radiatively inefflcient magnetized disc. An advection event, bringing flux of the opposite polarity, propagates inward leading, first, to a rise in the UV/optical luminosity and, then, to a dip in the X-ray luminosity. We find that the observed time-scale between the beginning of the changing-look event and the minimum in the X-ray luminosity, ≈200 d, is in agreement with the time needed to cancel the magnetic flux in a MAD extending to ≈180 rg . Although flux inversion events might be rare due to the large ratio of flux-to-mass that is needed, we argue that AGN showing an unusually high ratio of X-ray to UV luminosity are prime candidates for such events. We suggest that similar events may lead to jet interruptions in radio-loud objects.