Late-time observations of the relativistic tidal disruption flare candidate Swift J1112.2-8238

TL;DR

This study presents late-time observations of the relativistic tidal disruption flare candidate Swift J1112.2-8238, confirming its redshift, analyzing host galaxy morphology, and supporting the tidal disruption model with radio and positional data.

Contribution

It provides detailed late-time follow-up data, including host galaxy analysis and radio observations, strengthening the tidal disruption flare interpretation.

Findings

Host galaxy has complex, disturbed morphology.

Transient position is consistent with the galaxy's bulge.

Radio emission suggests similarity to other relativistic tidal disruption flares.

Abstract

We present late-time follow-up of the relativistic tidal disruption flare candidate Swift J1112.2-8238. We confirm the previously determined redshift of $z=0.8900\pm0.0005$ based on multiple emission line detections. {\em HST} imaging of the host galaxy indicates a complex and distorted morphology with at least two spatially distinct components. These are offset in velocity space by less than 350\,km\,s$^{-1}$ in VLT/X-Shooter observations, suggesting that the host is undergoing interaction with another galaxy. The transient position is consistent to 2.2$\sigma$ with the centre of a bulge-like component at a distance of 1.1$\pm$0.5\,kpc from its centre. Luminous, likely variable radio emission has also been observed, strengthening the similarities between Swift J1112.2-8238 and other previously identified relativistic tidal disruption flares. While the transient location is $\sim2\sigma$ from the host centroid, the disrupted nature of the host may provide an explanation for this. The tidal disruption model remains a good description for these events.