GCN Circular 40984
L. Cotter,C. McKenna, D. Murphy, C. de Barra, A. Ulyanov, P. McDermott, G. Finneran, M. Doyle, R. Dunwoody, J. Mangan, G. Corcoran, 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 GRB250703A (Fermi-GBM detection GCN 40909; IPN localization GCN 40976; Konus-Wind GCN 40977) by the Gamma-ray Module (GMOD) instrument. The GMOD detection was made, starting at 2025-07-03 09:07:31.6 UTC.
The GMOD light-curve for GRB250703A with 1.2s binning shows a single bright pulse starting at 09:07:31.6 UTC, also visible on the Fermi light-curve.
The spacecraft location at the time of detection was 47.364º N, 32.160º E, at an altitude of 361.2 km. The GMOD light curve for this event can be found here:
https://grb.eirsat1.ie/250703A/250703A_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 at University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023.