GRB 250702A

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

At 09:54:07 UT on 2 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250702A (trigger 773142852.561082 / 250702413).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 317.8, Dec = 48.1 (J2000 degrees, equivalent to J2000 21h 11m, 48d 06'), with a statistical uncertainty of 1.1 degrees.

The angle from the Fermi LAT boresight is 56.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702413/quicklook/glg_skymap_all_bn250702413.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702413/quicklook/glg_healpix_all_bn250702413.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702413/quicklook/glg_lc_medres34_bn250702413.gif

T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
773142852 at 09:54:07 on 02 July 2025 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position is:
RA(2000.0) = 324.3 deg
Decl.(2000.0) = 52.9 deg
The 1 sigma statistical error radius is 2.5 deg.
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB250702413/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB250702413/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB250702413/json

                        

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

"At 09:54:07.56 UT on 02 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250702A (trigger 773142852/250702413).
The Fermi-GBM position was reported in GCN 40883
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  (Fermi GBM Team 2025).

The angle from the Fermi LAT boresight is 56 degrees.

The GBM light curve consists of a single bright emission episode with a duration (T90)
of about 52.7 s (50-300 keV). The time-averaged spectrum
from T0 to T0+69 s is best fit by a Band function 
with Epeak= 242 +/- 9 keV, alpha =-0.57 +/- 0.03 and beta =-2.6 +/- 0.2.

A power law function with an exponential high-energy cutoff
fits the spectrum equally well with a power law index of -0.61 +/- 0.02 
and a cutoff energy, parameterized as Epeak, of 262 +/- 7 keV.

The event fluence (10-1000 keV) in this time interval is
(3.84 +/- 0.08)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.9 s in the 10-1000 keV band is 12.8 +/- 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/"

Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:

GECAM-B was triggered in-flight by the long burst GRB 250702A at 2025-07-02T09:54:07.850 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40881
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 ). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 24.0 +2.5/-4.5 s.

The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecamgrb250702A.png

This burst is incident from the back of satellite platform and the on-ground localization is subject by the Earth shadow of Fermi/GBM. With the localization from Fermi/GBM (RA=317.8, DEC=48.1, GCN#40881
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 ). The time-averaged spectrum from T0-2 s to T0+31 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.91 +0.20/-0.16 and the cutoff energy, parameterized as Epeak, is 417 +136/-93 keV. The event fluence (10-1000 keV) in this time interval is (3.85 +0..35/-0.41)E-05 erg/cm^2. 

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).

K. Kobayashi (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita,
Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
Y. Asaoka (ICRR), S. Torii, Y. Akaike,  (Waseda U), Y. Shimizu,
T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long GRB 250702A (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 40881
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 ; BALROG localization: Preis et al., GCN Circ 40882
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 ; Fermi GBM 
Detection: Malacaria et al., GCN Circ. 40887
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 ; GECAM-B detection: Wang et al.,
GCN Circ. 40992
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 ) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 
09:54:05.81 UTC on 2 July 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1435484973/index.html).
The burst signal was seen by all CGBM detectors.  

The burst light curve shows a single pulse that starts
at T+1.5 sec, peaks at T+6.2 sec, and ends at T+14.4 sec.
The T90 and T50 durations measured by the SGM data are 10.5 +/- 0.6 sec
and 3.9 +/- 0.3 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1435484973

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.