A DECam Search for Explosive Optical Transients in Association with IceCube Neutrino Alerts

We investigate the likelihood of association between TeV-PeV energy neutrino alerts from the IceCube Collaboration and core-collapse supernovae (CC SNe). We report results from triggered optical follow-up observations of three IceCube alerts (IC170922A, IC171106A, and IC181023A) with Blanco/DECam ($gri$ to 24th magnitude in $\sim6$ epochs). Using an automated pipeline to select CC SNe exploding in coincidence with neutrino alerts and a suite of simulated supernova light curves, we find that the DECam follow-up sequences are capable of significantly reducing background SNe contamination and creating a signal-dominated region for redshifts $z \leq 0.2$. For the alerts followed-up in this study, we find 5 objects that are likely CC SNe and spatially and temporally coincident with the neutrino alerts. A maximum likelihood analysis shows that we do not have the sensitivity to claim association between a single alert and a single optical candidate at a high confidence level, however, if CC SNe are the main source of TeV-PeV energy neutrinos, we find that $\sim50$ DECam follow-ups will be able to determine whether CC SNe contribute to the total TeV-PeV energy IceCube neutrino flux at the $4\sigma$ confidence level.