TITLE: GCN CIRCULAR NUMBER: 39517 SUBJECT: GRB 250225B: INTEGRAL SPI-ACS detection DATE: 25/02/27 14:29:04 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome aishth@outlook.com

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

GRB 250225B was discovered by Swift/BAT (GCN 39479) at 2025-02-25T19:39:13 (UTC) and has also been detected by SVOM/GRM (GCN 39493), Konus Wind (GCN 39498) and Fermi/GBM (GCN 39502).

In a SPI-ACS light curve above 80 keV, we find a signal temporally coincident with these detections, having an approximate duration of ~ 3 sec. The signal consists of a single pulse over this duration.

The approximate peak count rate in SPI-ACS is 90,000 cts/s for E>80 keV, over a median background rate of 70,800 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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