A tidal disruption event in the nearby ultra-luminous infrared galaxy F01004-2237

TL;DR

This paper reports the first detection of a tidal disruption event (TDE) in a nearby ultra-luminous infrared galaxy, suggesting TDEs may be more common in such starburst galaxies than previously thought.

Contribution

It presents the discovery of a TDE in F01004-2237, a galaxy with ongoing starburst activity, indicating higher TDE rates in ultra-luminous infrared galaxies.

Findings

Detection of strong, broad helium emission lines after a luminous optical flare.

The event's spectral features are unlike supernovae or active galactic nuclei.

TDE rate in ultra-luminous infrared galaxies may be significantly higher.

Abstract

Tidal disruption events (TDEs), in which stars are gravitationally disrupted as they pass close to the supermassive black holes in the centres of galaxies, are potentially important probes of strong gravity and accretion physics. Most TDEs have been discovered in large-area monitoring surveys of many 1000s of galaxies, and the rate deduced for such events is relatively low: one event every 10$^4$ - 10$^5$ years per galaxy. However, given the selection effects inherent in such surveys, considerable uncertainties remain about the conditions that favour TDEs. Here we report the detection of unusually strong and broad helium emission lines following a luminous optical flare (Mv < -20.1 mag) in the nucleus of the nearby ultra-luminous infrared galaxy F01004-2237. The particular combination of variability and post-flare emission line spectrum observed in F01004-2237 is unlike any known supernova or active galactic nucleus. Therefore, the most plausible explanation for this phenomenon is a TDE -- the first detected in a galaxy with an ongoing massive starburst. The fact that this event has been detected in repeat spectroscopic observations of a sample of 15 ultra-luminous infrared galaxies over a period of just 10 years suggests that the rate of TDEs is much higher in such objects than in the general galaxy population.