GCN Circular 39781

C. McKenna, D. Murphy, C. de Barra, A. Ulyanov, P. McDermott, G. Finneran,  M. Doyle, R. Dunwoody, J. Mangan, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: 

EIRSAT-1 reports the detection of the long gamma-ray burst GRB 250317D by the Gamma-ray Module (GMOD) instrument, which also triggered Fermi GBM (Fermi Trigger 763933627 / bn250317824, retrieved from Fermi GBM burst catalog [von Kienlin, A. et al. 2020, Gruber, D. et al. 2014, von Kienlin, A. et al. 2014, and Bhat, P. et al. 2016])

The GMOD detection was made starting at 2025-03-17 19:47:53.5 UTC.

The GMOD light-curve for GRB 250317D with 1.2s binning shows a bright pulse starting at 19:47:53.5 UTC, also visible on the Fermi light-curve, followed by a less significant second pulse of one bin width. The pulses seen earlier than this time in the Fermi light-curve cannot be distinguished against the background in the GMOD light-curve.

The spacecraft location at the time of detection was 17.359 N, 35.838 E, at an altitude of 414.30 km.

The GMOD light curve for this event can be found here: 
https://grb.eirsat1.ie/250317D/250317D_LC_onboard_preliminary.png 

EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023.