AT2020ohl: its nature and probable implications

Document Type

Article

Publication Title

Monthly Notices of the Royal Astronomical Society

Abstract

ASASSN-20hx, a.k.a AT2020ohl, is an ambiguous nuclear transient, which was disco v ered in the nearby galaxy NGC6297 by the All-Sk y Automated Surv e y for Superno vae. We hav e inv estigated the evolution of AT2020ohl using a multiwavelength data set to explain the geometry of the system and the energy radiated by it between X-ray and radio wavelengths. Our X-ray, UV/optical, and radio observations of the object jointly clarify the association of AT2020ohl with the nuclear activity of NGC6297. We detected radio counterpart of AT2020ohl 111 and 313 d after the disco v ery in Jansky Very Large Array X-band with flux densities 47 ±14 and 34 ±3 μJy, respectively . Using multiwavelength data analysis, we nullify the possibility of associating any stellar disruption process with this event. We found some evidence showing that the host galaxy is a merger remnant, so the possibility of a binary supermassive black hole (SMBH) system cannot be ruled out. The central SMBH has a mass of ~1.2 ×107 M⊙. We propose the accretion disc activity as the origin of AT2020ohl -it is either due to disc accretion event on to the central SMBH or due to the sudden accretion activity in a pre-existing accretion disc of the system during the interaction of two SMBHs which became gravitationally bound during a merger process. Ho we ver, we also admit that with the existing data set, it is impossible to say definitively, among these two probabilities, which one is the origin of this nuclear transient.

First Page

6176

Last Page

6192

DOI

10.1093/mnras/stae395

Publication Date

3-1-2024

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