Automated rapid follow-up of Swift GRBs with AMI-LA

TL;DR

This paper demonstrates rapid automated radio follow-up observations of Swift GRBs using AMI-LA, achieving early constraints on radio emission and detecting afterglow in one case, with new software tools for systematic transient follow-up.

Contribution

It introduces an automated system for rapid radio follow-up of GRBs and details new software tools for alert handling and robotic observatory control.

Findings

First millijansky-level constraints within an hour post-burst

Radio afterglow detected from GRB120326A days after the burst

Automated follow-up initiated within five minutes of GRB alerts

Abstract

We present 15-GHz follow-up radio observations of eleven Swift gamma-ray burst (GRB) sources, obtained with the Arcminute Microkelvin Imager Large Array (AMI-LA). The initial follow-up observation for each source was made in a fully automated fashion; as a result four observations were initiated within five minutes of the GRB alert timestamp. These observations provide the first millijansky-level constraints on prolonged radio emission from GRBs within the first hour post-burst. While no radio emission within the first six hours after the GRB is detected in this preliminary analysis, radio afterglow is detected from one of the GRBs (GRB120326A) on a timescale of days. The observations were made as part of an ongoing programme to use AMI-LA as a systematic follow-up tool for transients at radio frequencies. In addition to the preliminary results, we explain how we have created an easily extensible automated follow-up system, describing new software tools developed for astronomical transient alert distribution, automatic requesting of target-of-opportunity observations, and robotic control of the observatory.