The Atacama Cosmology Telescope: Flux Upper Limits from a Targeted Search for Extragalactic Transients

Understand

We have performed targeted searches of known extragalactic transient events at millimetre wavelengths using nine seasons (2013--2021) of 98, 150, and 229\,GHz Atacama Cosmology Telescope (ACT) observations that mapped ${\sim}40$ per cent of the sky for most of the data volume.

• Our data cover 88 gamma-ray bursts (GRBs), 12 tidal disruption events (TDEs) and 203 other transients, including supernovae (SNe).
• We stack our ACT observations to increase the signal-to-noise ratio of the maps.
• In all cases but one, we do not detect these transients in the ACT data.