TITLE: GCN CIRCULAR NUMBER: 39342 SUBJECT: GRB 250215A: Fermi GBM Observation DATE: 25/02/16 07:17:46 GMT FROM: Lorenzo Scotton at UAH lscottongcn@outlook.com

L. Scotton (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 02:31:54.94 UT on 15 February 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250215A (trigger 761279519/250215105), which was also detected by EP-WXT and FXT (Wang et al., GCN 39329), INTEGRAL SPI-ACS (Barria et al., GCN 39331), AstroSat CZTI (Tembhurnikar et al., GCN 39334), SVOM/GRM (Zheng et al., GCN 39335) and Swift-XRT (Page et al., GCN 39336).

NOT (Liu et al., GCN 39330, Malesani et al., GCN 39341), SVOM/VT (Xie et al., GCN 39333) and Gemini-South (Malesani et al., GCN 39339) detected the optical counterpart.

The Fermi GBM on-ground location is consistent with the Swift-XRT position.

The angle from the Fermi LAT boresight is 28 degrees.

The GBM light curve consists of multiple emission episodes with a duration (T90) of about 13.4 s (50-300 keV). The time-averaged spectrum from T0-0.8 to T0+14.5 s is best fit by a Band function with Epeak = 117 +/- 9 keV, alpha = -0.68 +/- 0.09 and beta = -2.38 +/- 0.14.

The event fluence (10-1000 keV) in this time interval is (6.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+12 s in the 10-1000 keV band is 11.1 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

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