GRB 241025C

The Fermi GBM team reports the detection of a likely SHORT GRB

"At 15:36:10.66 UT on 25 October 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 241025C (trigger 751563375/241025650).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 152.56, Dec = 48.27 (J2000 degrees, equivalent to J2000 10h 10m, +48d 16'),
with a statistical uncertainty of 2.29 degrees.

The angle from the Fermi LAT boresight is 75 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025650/quicklook/glg_skymap_all_bn241025650.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025650/quicklook/glg_healpix_all_bn241025650.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn241025650/quicklook/glg_lc_medres34_bn241025650.gif"

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

"At 15:36:10.66 UT on 25 October 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 241025C (trigger 751563375/241025650).

The GBM on-ground calculated location was reported in GCN Circular 37883
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 .

The angle from the Fermi LAT boresight is 75 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 5 s (50-300 keV). The time-averaged spectrum
from T0-3.0 to T0+3.2 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.68 +/- 0.13 and the cutoff energy,
parameterized as Epeak, is 103 +/- 7 keV.

The event fluence (10-1000 keV) in this time interval is
(1.71 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.26 s in the 10-1000 keV band is 9.7 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well with
Epeak = 102 +/- 10 keV, alpha = -0.68 +/- 0.15 and beta = -3.68 +/- 2.34.

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/"

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The short-duration GRB 241025C (Fermi/GBM detection: GCN 37887
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 ; Konus/Wind detection at 2024-10-25 15:36:11.902 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-10-25 15:36:09 UTC. The T90 duration is 2 s and the significance during T90 reaches 7.9 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB241025C_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.