A New AGILE MCAL Configuration to Detect Gamma-Ray Bursts and Sub-threshold Events in the Multimessenger Era

Abstract

Starting in 2016 August, the onboard software configuration of the Astrorivelatore Gamma ad Immagini LEggero (AGILE) MiniCALorimeter (MCAL) was modified in order to increase the instrument trigger capabilities for the detection of short duration high-energy transients, such as weak gamma-ray sub-threshold events and short gamma-ray bursts. MCAL is a nonimaging, all-sky detector, operating in the energy range 0.4–100 MeV. This change was carried out in order to make AGILE more competitive in the detection of electromagnetic counterparts to gravitational wave events revealed by the Laser Interferometer Gravitational-Wave Observatory/Virgo experiments. In the 22 months from 2016 August to 2018 May, the new adopted MCAL-GW configuration substantially enhanced the number of MCAL onboard triggers, increasing the total acquisition time of the instrument, and resulted in the detection of 52 bursts, 40 of which have been confirmed by the InterPlanetary Network.