A fast rising tidal disruption event from a candidate intermediate mass black hole

TL;DR

This paper reports the discovery of a fast rising tidal disruption event (TDE) in a dwarf galaxy, providing evidence for an intermediate mass black hole and suggesting a new method to measure black hole masses in such galaxies.

Contribution

It presents the identification of a rare, fast rising TDE candidate in a dwarf galaxy, indicating the presence of an intermediate mass black hole and proposing a novel approach to measure IMBH masses.

Findings

AT2020neh is a fast rising TDE candidate in a dwarf galaxy.

The black hole mass involved is estimated between 10^{4.7} and 10^{5.9} solar masses.

The observable rate of such events is very low, less than 2 x 10^{-8} events per Mpc^3 per year.

Abstract

Massive black holes (BHs) at the centres of massive galaxies are ubiquitous. The population of BHs within dwarf galaxies, on the other hand, is evasive. Dwarf galaxies are thought to harbour BHs with proportionally small masses, including intermediate mass BHs, with masses $10^{2} < M_{BH} < 10^{6} M_{\odot}$. Identification of these systems has historically relied upon the detection of light emitted from accreting gaseous discs close to the BHs. Without this light, they are difficult to detect. Tidal disruption events (TDEs), the luminous flares produced when a star strays close to a BH and is shredded, are a direct way to probe massive BHs. The rise times of these flares theoretically correlate with the BH mass. Here we present AT2020neh, a fast rising TDE candidate, hosted by a dwarf galaxy. AT2020neh can be described by the tidal disruption of a main sequence star by a 10$^{4.7} - 10^{5.9} M_{\odot}$ BH. We find the observable rate of fast rising nuclear transients like AT2020neh to be rare, at $\lesssim 2 \times 10^{-8}$ events Mpc$^{-3}$ yr$^{-1}$. Finding non-accreting BHs in dwarf galaxies is important to determine how prevalent BHs are within these galaxies, and constrain models of BH formation. AT2020neh-like events may provide a galaxy-independent method of measuring IMBH masses.