A Tidal Flare Candidate in Abell 1795

TL;DR

This paper reports the discovery of a strong, long-lasting X-ray transient in Abell 1795, likely a tidal disruption event indicating a massive black hole in a dwarf galaxy, with extensive observational data supporting this interpretation.

Contribution

It presents one of the best-sampled tidal flare candidates with multi-year X-ray observations and links it to potential EUV detection, offering new insights into tidal disruption events in cluster environments.

Findings

Extreme variability and supersoft spectrum consistent with tidal disruption

Long duration and high luminosity support tidal flare interpretation

Possible EUV counterpart suggests early high luminosity phase

Abstract

As part of our ongoing archival X-ray survey of galaxy clusters for tidal flares, we present evidence of an X-ray transient source within 1 arcmin of the core of Abell 1795. The extreme variability (a factor of nearly 50), luminosity (> 2 x 10^42 erg s^{-1}), long duration (> 5 years) and supersoft X-ray spectrum (< 0.1 keV) are characteristic signatures of a stellar tidal disruption event according to theoretical predictions and to existing X-ray observations, implying a massive >~10^5 M_sun black hole at the centre of that galaxy. The large number of X-ray source counts (~700) and long temporal baseline (~12 years with Chandra and XMM-Newton) make this one of the best-sampled examples of any tidal flare candidate to date. The transient may be the same EUV source originally found contaminating the diffuse ICM observations of Bowyer et al. (1999), which would make it the only tidal flare candidate with reported EUV observations and implies an early source luminosity 1-2 orders of magnitude greater. If the host galaxy is a cluster member then it must be a dwarf galaxy, an order of magnitude less massive than the quiescent galaxy Henize 2-10 which hosts a massive black hole that is difficult to reconcile with its low mass. The unusual faintness of the host galaxy may be explained by tidal stripping in the cluster core.