TITLE: GCN CIRCULAR NUMBER: 39236 SUBJECT: GRB 250206A: EIRSAT-1 GMOD Detection DATE: 25/02/08 15:43:17 GMT FROM: Caimin McKenna at University College Dublin caimin.mckenna@ucdconnect.ie

D. Murphy, C. McKenna, C. de Barra, A. Ulyanov, P. McDermott, M. Doyle, R. Dunwoody, J. Mangan, G. Finneran, 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 GRB250206A by the Gamma-ray Module (GMOD) instrument, which was also detected by Fermi GBM (GCN [39172](https://gcn.nasa.gov/circulars/39172)). The detection was made starting at 2025-02-06 19:51:22.4 UTC.

The GMOD light curve for GRB250206A with 1.2s binning shows a long burst with two pulses, separated by 7.2 seconds, consistent with that seen by NASA Fermi-GBM. The 3rd softer pulse is not detected by GMOD. The spacecraft location at the time of detection was 5.095 N, 35.194 E at an altitude of 439.8 km.

The GMOD light curve for this event can be found here: https://grb.eirsat1.ie/250206A/250206A_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.

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