Millimeter Transient Point Sources in the SPTpol 100 Square Degree Survey

TL;DR

This study utilizes the South Pole Telescope's high-resolution millimeter observations to search for transient sources, aiming to uncover unknown phenomena like gamma-ray burst afterglows in the millimeter band.

Contribution

It demonstrates the potential of CMB telescopes for detecting millimeter transient sources, a novel application beyond their primary cosmic microwave background measurements.

Findings

One candidate transient consistent with a gamma-ray burst afterglow was identified.

No statistically significant transient sources were confirmed during the observation period.

The survey established upper limits on the rate of millimeter transients at 10 mJy.

Abstract

The millimeter transient sky is largely unexplored, with measurements limited to follow-up of objects detected at other wavelengths. High-angular-resolution telescopes designed for measurement of the cosmic microwave background offer the possibility to discover new, unknown transient sources in this band, particularly the afterglows of unobserved gamma-ray bursts. Here we use the 10-meter millimeter-wave South Pole Telescope, designed for the primary purpose of observing the cosmic microwave background at arcminute and larger angular scales, to conduct a search for such objects. During the 2012-2013 season, the telescope was used to continuously observe a 100 square degree patch of sky centered at RA 23h30m and declination -55 degrees using the polarization-sensitive SPTpol camera in two bands centered at 95 and 150 GHz. These 6000 hours of observations provided continuous monitoring for day- to month-scale millimeter-wave transient sources at the 10 mJy level. One candidate object was observed with properties broadly consistent with a gamma-ray burst afterglow, but at a statistical significance too low (p=0.01) to confirm detection.