TITLE: GCN CIRCULAR NUMBER: 39518 SUBJECT: EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection DATE: 25/02/27 14:31:11 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome aishth@outlook.com

Aishwarya Linesh Thakur(a), James Craig Rodi(a), Patrizia Barria(a,b), Giulia Gianfagna(a), Luigi Piro(a), Lorenzo Natalucci(a,b) report:

EP250226a/GRB 250226A was discovered by Fermi/GBM (GCN 39479) and EP-WXT (GCN 39482) at 2025-02-26T06:34:57 (UTC) and has also been detected by GECAM-B (GCN 39492)

In a SPI-ACS light curve above 80 keV, we find a signal temporally coincident with the GBM and EP-WXT detections, having an approximate duration of ~ 15 sec. The signal consists of a single pulse over this duration. This signal is also detected marginally in the IBIS/PICsIT data.

The approximate peak count rate in SPI-ACS is 74,000 cts/s for E>80 keV, over a median background rate of 67,600 cts/s.

This work is based on observations with INTEGRAL, an ESA project with instruments and a science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, and Spain), and with the participation of Russia and the USA. The SPI-ACS detector system has been provided by MPE Garching/Germany.

----- (a) INAF/IAPS-Rome (b) ICSC National Research Centre for High-Performance Computing

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