An accretion disc with magnetic outflows triggered by a sudden mass accretion event in changing-look active galactic nucleus 1ES 1927+654

Abstract

1ES 1927+654 was known as a type 2 Seyfert galaxy, which exhibited drastic variability recently in ultraviolet (UV)/optical and X-ray bands. An UV/optical outburst was observed in the end of 2017, and it reached the peak luminosity ∼50 days later. The high-cadence observations showed a rapid X-ray flux decline with complete disappearance of the power-law hard X-ray component when the soft X-ray thermal emission reached its lowest level about 150 days after the UV/optical peak. The power law X-ray component reappeared with thermal X-ray emission brightening from its lowest flux within next ∼ 100 days. We assume an episodic accretion event taking place in the outer region of the disc surrounding a central black hole (BH), which is probably due to a red giant star tidally disrupted by the BH. The inner thin disc with corona is completely swept by the accretion event when the gas reaches the innermost circular stable orbit. The field threading the disrupted star is dragged inwards by the disc formed after the tidal disruption event, which accelerates outflows from the disc. The disc dimmed since a large fraction of the energy released in the disc is tapped into the outflows. The accretion rate of the episodic accretion event declines, and ultimately it turns out to be a thin disc, which is inefficient for field advection, and the outflows are switched off. A thin disc with corona reappears later after the outburst.

The Peak of the Fallback Rate from Tidal Disruption Events: Dependence on Stellar Type

“…For example, the ∼decades-long X-ray outburst from the galaxy GSN 069, which was recently found to exhibit quasiperiodic eruptions (Miniutti et al 2019(Miniutti et al , 2023a(Miniutti et al , 2023b, was argued to be due to the disruption of a massive star (Sheng et al 2021). Similar claims in the context of other putative TDEs have been made by Lin et al (2017), Yan & Xie (2018), Cao et al (2023), and Subrayan et al (2023). In Lin et al (2017) in particular, the authors note that the disruption of a 10 M e star can explain a long-duration X-ray flare lasting over ∼11 yr.…”

Study of Asymptotic Velocity in the Bondi–Hoyle Accretion Flows in the Domain of Kerr and 4-D Einstein–Gauss–Bonnet Gravities

“…The amplitude of the radiation changes over time. They may be also source of sudden bursts (Cao et al 2023). As seen in section 5.4, fundamental modes of oscillation create new frequencies by non-linear coupling.…”

Changing-Look Narrow-Line Seyfert 1 Galaxies, their Detection with SVOM, and the Case of NGC 1566

“…Some have explored extinction variability, for instance through dusty material crossing our line of sight or alternatively by dust destruction in response to an outburst [2]. The majority of theoretical models has focused on short-term changes in the accretion rate (on the time scale of months-decades), for instance due to disk instabilities or other mechanisms (e.g., the radiation pressure disk instability, the Hydrogen ionization instability, magneticpressure-supported disks, magnetic flux inversion, instabilities in warped disks at large radii, or shock formation in highly precessing disks ) (e.g., [3][4][5][6][7][8][9][10][11][12][13][14][15]) or have explored the possibility of tidal disk interactions in binary SMBH systems [16].…”