The Arcminute Microkelvin Imager catalogue of gamma-ray burst afterglows at 15.7 GHz

Abstract

We present the Arcminute Microkelvin Imager (AMI) Large Array catalogue of 139 gamma-ray bursts (GRBs). AMI observes at a central frequency of 15.7 GHz and is equipped with a fully automated rapid-response mode, which enables the telescope to respond to highenergy transients detected by Swift. On receiving a transient alert, AMI can be on-target within two minutes, scheduling later start times if the source is below the horizon. Further AMI observations are manually scheduled for several days following the trigger. The AMI GRB programme probes the early-time (< 1 day) radio properties of GRBs, and has obtained some of the earliest radio detections (GRB 130427A at 0.36 and GRB 130907A at 0.51 days post-burst). As all Swift GRBs visible to AMI are observed, this catalogue provides the first representative sample of GRB radio properties, unbiased by multi-wavelength selection criteria. We report the detection of six GRB radio afterglows that were not previously detected by other radio telescopes, increasing the rate of radio detections by 50% over an 18-month period. The AMI catalogue implies a Swift GRB radio detection rate of 15%, down to ∼ 0.2 mJy/beam. However, scaling this by the fraction of GRBs AMI would have detected in the Chandra & Frail sample (all radio-observed GRBs between 1997 − 2011), it is possible ∼ 44 − 56% of Swift GRBs are radio bright, down to ∼ 0.1 − 0.15 mJy/beam. This increase from the Chandra & Frail rate (∼ 30%) is likely due to the AMI rapid-response mode, which allows observations to begin while the reverse-shock is contributing to the radio afterglow.

Detailed multiwavelength modelling of the dark GRB 140713A and its host galaxy

“…Non-detections are given as 3σ upper-limits. The AMI data are identical to those quoted in Anderson et al (2018). AMI (Perrott et al 2013).…”

“…On responding to the Swift-BAT trigger of GRB 140713A, AMI was observing the event within 6 min for 2 hrs, obtaining a 3σ flux upper-limit of 0.27 mJy. Followup observations were manually scheduled and obtained every few days for over 2 months, with the first confirmed detection occurring 3.19 d post-burst (Anderson et al 2018). AMI data were reduced using the AMIsurvey software package (Staley & Anderson 2015c), which utilises the AMI specific data reduction software ami-reduce (Dickinson et al 2004) and chimenea, which is built upon the Common Astronomy Software Application (CASA; Jaeger 2008) package and specifically designed to clean and image multi-epoch transient data (Staley & Anderson 2015a,b).…”

“…AMI (Perrott et al 2013). For further details on the reduction and analysis we performed on the AMI observations, see Anderson et al (2018).…”

A detailed radio study of the energetic, nearby, and puzzling GRB 171010A

“…As part of a GRB afterglow followup campaign (Anderson et al 2018) we began observing GRB 171010A using the AMI-LA at T 0 + 1.27 d. An initial 4 hour observation was conducted at a central frequency of 15.5 GHz with a 5 GHz bandwidth spread over 4096 channels. Data were reduced using the Common Astronomical Software Applications ( ) package with a custom reduction pipeline, which flagged the data for radio frequency interference and instrumental effects, and calibrated the flux, bandpass and phases.…”

Standardizing VOEvents and archives

“…The VO network and the VOEvent framework are developed and maintained by the International Virtual Observatory Alliance (IVOA). A number of tools and libraries have been developed using the IVOA standard to interface with the network and facilitate use by the community such as the Comet broker system 3 [1] and the 4 Pi Sky transient research project 4 [2]. These systems are currently used by many transient facilities, such as the Neil Gehrels Swift satellite which communicates new gamma ray burst (GRB) detections via VOEvent which can be subsequently followed up at other facilities [3].…”