TITLE:   GCN CIRCULAR
NUMBER:  37231
SUBJECT: GRB240821B: First GRB Detected by EIRSAT-1 GMOD
DATE:    24/08/22 17:57:02 GMT
FROM:    David Murphy <david.murphy@ucd.ie>

D. Murphy, C. McKenna, C. de Barra, A. Ulyanov, P. McDermott, M. Doyle, R. Dunwoody, J. Mangan, G. Finneran, 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 GRB240821B by the Gamma-ray Module (GMOD) instrument, which was also detected by Fermi GBM (GCN [37224](https://gcn.nasa.gov/circulars/37224)). The detection was made at 24-08-21 17:17:35.6 UTC.

The GMOD light curve for GRB240821B with 1.2s binning shows a burst with multiple pulses. The spacecraft location at time of detection was 38.677 N, 65.093 E and an altitude of 481.9 km.

The GMOD light curve for this event can be found here: 
https://grb.eirsat1.ie/20240821B/20240821B_LC_onboard_preliminary.png

EIRSAT-1 is Ireland’s first satellite ([Doyle et al. Proceedings of the 4th SSEA, 2022](https://researchrepository.ucd.ie/bitstreams/2f3fdccb-6e36-4ac1-88cd-4e80feecf446/download)). 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](https://link.springer.com/article/10.1007/s10686-022-09842-z)). 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.