2025A&A...695A.228N

Context. Observations of transient emission from extreme accretion events onto supermassive black holes can reveal conditions in the center of galaxies and the black hole itself. Most recently, it has been suggested these sources could be emitters of high-energy neutrinos. However, in most cases, it remains unclear whether this would be classified as the outcome of rejuvenated accretion or a tidal disruption event (TDE).
Aims. We expand on existing samples of infrared (IR) flares to compile the largest and most complete list available. A large sample size is necessary to provide high-enough statistics for distant and faint objects to estimate their rates. Our catalog is large enough to facilitate a preliminary study of the rate evolution with redshift for the first time.
Methods. We compiled a sample of 40 million galaxies. Using a custom, publicly available pipeline, we analyzed the WISE light curves for these 40 million objects using the Bayesian Blocks algorithm. We selected promising for dust echo candidates involved in transient accretion events and we inferred the luminosity, extension, and temperature of the hot dust by fitting a blackbody spectrum.
Results. We established a clean sample of 823 dust echo-like IR flares, dubbed the Flaires catalog. For 568 of them, we were able to estimate the dust properties. After removing 70 objects with possible contributions from synchrotron emission, the luminosity, extension, and temperature are consistent with dust echos. Estimating the dust extension from the light curve shape revealed that the duration of the incident flare is broadly compatible with the duration of TDEs. The resulting rate per galaxy is consistent with the latest measurements of IR-detected TDEs and appears to decline with increasing redshift.
Conclusions. Although systematic uncertainties may impact the calculation of the rate evolution, this catalog will enable further research of phenomena related to dust echos from TDEs and extreme accretion flares.