The Atacama cosmology telescope: flux upper limits from a targeted search for extragalactic transients

Carlos Hervías-Caimapo, Sigurd Naess, Adam D. Hincks, Erminia Calabrese, Mark J. Devlin, Jo Dunkley, Rolando Dünner, Patricio A. Gallardo, Matt Hilton, Anna Y.Q. Ho, Kevin M. Huffenberger, Xiaoyi Ma, Mathew S. Madhavacheril, Michael D. Niemack, John Orlowski-Scherer, Lyman A. Page, Bruce Partridge, Roberto Puddu, Maria Salatino, Cristóbal SifónSuzanne T. Staggs, Cristian Vargas, Eve M. Vavagiakis, Edward J. Wollack

Research output: Contribution to journalArticlepeer-review


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 ∼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. The single candidate detection (event AT2019ppm), seen at ∼5σ significance in our data, appears to be due to active galactic nuclei activity in the host galaxy coincident with a transient alert. For each source in our search we provide flux upper limits. For example, the medians for the 95 per cent confidence upper limits at 98 GHz are 15, 18, and 16 mJy for GRBs, SNe, and TDEs, respectively, in the first month after discovery. The projected sensitivity of future wide-area cosmic microwave background surveys should be sufficient to detect many of these events using the methods described in this paper.

Original languageEnglish (US)
Pages (from-to)3020-3034
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Apr 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • cosmic background radiation
  • methods: data analysis
  • transients: gamma-ray bursts
  • transients: supernovae
  • transients: tidal disruption events


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