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Description
When a star passes too close to a supermassive black hole, it gets disrupted and torn apart by the tidal forces in an event known as a tidal disruption event (TDE). The emission from TDEs is observed across the electromagnetic spectrum, with the majority discovered in ultraviolet and optical wavelengths. However, an increasing number of TDEs have been observed to exhibit long-lasting infrared (IR) echoes. These echoes arise when dust residing in the nuclear regions of a galaxy absorbs the ultraviolet and optical radiation and reprocesses it into the infrared. Studying these IR echoes can reveal intricate properties of the dust residing in nuclear regions of quiescent galaxies and gives us a chance to observe TDEs otherwise fully or partially obscured by dust.
We present an ongoing systematic study of IR echoes from a sample of young TDEs observed with the Nordic Optical Telescope (NOT) and the Wide-field Infrared Survey Explorer (WISE). Near- and mid-IR photometry from NOT and WISE, respectively, combined with ultraviolet and optical data, allows us to trace the temporal evolution of the dust emission. We do this by using modified blackbody and IR echo models to constrain dust temperatures and geometries of the emitting regions, including the distance of such dust. These measurements enable a detailed view of the IR echoes and provide insight into the properties of the TDEs themselves, as we can assess if the optical to infrared spectral energy distribution exhibits longer-lived emission at longer wavelengths consistent with a dust echo, or bluer and fast declining emission caused by the free-free processes in the dense reprocessing envelope of the TDE.