4PiSky Authors: Gemma Anderson / Tim Staley / Rob Fender

ADS Link: http://adsabs.harvard.edu/abs/2014MNRAS.440.2059A

AMI-LA Rapid Response Mode (ALARRM) observations of the nearby bright gamma-ray burst GRB 130427A allowed the 4 Pi Sky team to obtain one of the earliest radio detections of a GRB to date. As soon as this GRB had risen above the horizon the AMI-LA quickly slewed to its position detecting radio emission within 8 hours post-burst. Further follow-up AMI observations showed the radio flux to increase in brightness before rapidly declining one day later. Such a sudden decline in radio emission is very rare and has only been observed from a few GRBs.

The AMI 15.7 GHz and VLA 14 GHz light curve of GRB 130427A overplotted with the afterglow model derived by Perley et al. (2014, solid line) showing the individual contributions from the reverse shock (short dashed line) and forward shock (long dashed line). The AMI peak at 16 hrs is one of the earliest radio peaks ever observed from a GRB.

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