Extragalactic Millimeter Transients in the Era of Next Generation CMB Surveys

TL;DR

Next-generation CMB surveys will enable the discovery and study of various extragalactic millimeter transients, including gamma-ray bursts and tidal disruption events, by leveraging their wide-field, high-cadence capabilities.

Contribution

This work assesses the potential of upcoming CMB experiments to detect and characterize extragalactic transients using simulations and existing transient models.

Findings

Existing surveys will detect tens to hundreds of long gamma-ray bursts.

Next-generation experiments will find tens of fast blue optical transients.

CMB-HD will detect a few tidal disruption events and some short gamma-ray bursts.

Abstract

The next generation of wide-field cosmic microwave background (CMB) surveys are uniquely poised to open a new window for time-domain astronomy in the millimeter band. Here we explore the discovery phase space for extragalactic transients with near-term and future CMB experiments to characterize the expected population. We use existing millimeter-band light curves of known transients (gamma-ray bursts, tidal disruption events, fast blue optical transients, neutron star mergers) and theoretical models, in conjunction with known and estimated volumetric rates. Using Monte Carlo simulations of various CMB survey designs (area, cadence, depth, duration) we estimate the detection rates and the resulting light curve characteristics. We find that existing and near-term surveys will find tens to hundreds of long-duration gamma-ray bursts (LGRBs), driven primarily by detections of the reverse shock emission, and including off-axis LGRBs. Next-generation experiments (CMB-S4, CMB-HD) will find tens of fast blue optical transients (FBOTs) in the nearby universe and will detect a few tidal disruption events. CMB-HD will additionally detect a small number of short gamma-ray bursts, where these will be discovered within the detection volume of next generation gravitational wave experiments like Cosmic Explorer.