GRB 250612C
GCN Circular 40757
Subject
IPN triangulation of GRB 250612C (short/hard)
Date
2025-06-17T16:02:15Z (5 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi-GBM team,
and
Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier
on behalf of the SVOM-GRM team, report:
The bright, short-duration GRB 250612C
(Fermi-GBM detection: The Fermi GBM team, GCN 40704;
Neights and Meegan, GCN 40713;
BALROG localization: Preis and Greiner, GCN 40706;
SVOM-GRM detection: Wang et al., GCN 40708;
GRID detection: Yang et al., GCN 40732;
Konus-Wind detection: Frederiks et al., GCN 40746)
was detected by Fermi (GBM trigger 771432801), SVOM (GRM), Konus-Wind,
and GRID at about 53596 s UT (14:53:16).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
-------------------------------
RA(2000), deg Dec(2000), deg
-------------------------------
Center:
115.493 18.574
Corners:
116.886 22.070
116.633 22.036
113.718 15.372
113.864 15.182
--------------------------------
The error box area is 5.5 sq. deg, and its maximum
dimension is 7 deg (the minimum one is 14.7 arcmin).
The Sun distance was 33 deg.
This localization may be improved.
The IPN localization is consistent with, but reduces the area of,
the Fermi-GBM (GCN 40704) and BALROG (GCN 40706) localizations.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250612_T53591/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.
GCN Circular 40746
Subject
Konus-Wind detection of GRB 250612C (short/hard with extended emission)
Date
2025-06-16T11:33:32Z (5 months ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The bright GRB 250612C (Fermi GBM detection: Fermi GBM team, GCN 40704;
Neights & Meegan, GCN 40713; SVOM/GRM observation: Wang et al., GCN 40708;
GRID detection: Yang et al., GCN 40732)
triggered Konus-Wind (KW) at T0=53591.512 s UT (14:53:11.512).
The burst light curve shows a very bright, multi-peaked emission episode,
which starts at ~T0-0.05 s and has a duration of ~1.3 s.
This episode is followed by a much weaker extended emission tail visible to ~T0+25 s.
The emission is seen up to ~15 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250612_T53591/
As observed by Konus-Wind, the burst had the total fluence
of (6.92 ± 0.50)x10^-5 erg/cm^2 and a 16-ms peak energy flux,
measured from T0+0.016, of (3.01 ± 0.38)x10^-4 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the initial episode (measured from T0 to T0+1.280 s)
is best fit in the 20 keV - 20 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.90(-0.03,+0.02) and Ep = 2084 (-97,+103) keV (chi2 = 91.8/74 dof).
Fitting this spectrum by a Band function yields similar, within errors,
values of alpha and Ep, and an upper limit on the high energy photon index beta
of -4.0 (chi2 = 91.7/73 dof).
The spectrum near the peak count rate (measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 20 MeV range by a CPL model with
alpha = -0.14(-0.13,+0.14) and Ep = 2073 (-214,+263) keV (chi2 = 38.7/35 dof).
Fitting this spectrum by a Band function yields the same values of alpha and Ep,
and an upper limit on the high energy photon index beta of -2.0 (chi2 = 38.4/34 dof).
The spectrum of the extended emission, measured from T0+1.280 s to T0+25.856 s,
is best fit in the 20 keV - 20 MeV range by a simple power law (PL) function with
the photon PL index of -1.68 ± 0.12.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 40732
Subject
GRID detection of GRB 250612C
Date
2025-06-15T16:40:18Z (5 months ago)
From
GRID Student Team at Tsinghua University <grid@tsinghua.edu.cn>
Via
Web form
Zirui Yang, Longhao Li and Chenyu Wang report on behalf of the GRID Collaboration:
GRID-11B reports the detection of the GRB 250612C, which was also detected by Fermi/GBM (GCN Circular 40704) and SVOM/GRM (GCN Circular 40708).
The event was triggered with GRID on 2024-06-12 at 14:53:16 UTC. The measured burst duration (T90) is approximately 2.6 ± 0.9 seconds.
The GRID light curve of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB250612C/GRID_GRB250612C_ltcv.pdf.
GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4.
GCN Circular 40713
Subject
GRB 250612C: Fermi GBM Observation
Date
2025-06-12T21:54:11Z (5 months ago)
From
eliza.neights@gmail.com
Via
Web form
E. Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 14:53:16.58 UT on 12 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250612C (trigger 771432801/250612620).
which was also detected by SVOM/GRM (Wang et al. 2025, GCN 40708).
The Fermi-GBM position was reported in GCN 40708 (Fermi GBM Team 2025).
The angle from the Fermi LAT boresight is 96 degrees.
The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 1.62 s (50-300 keV). The time-averaged spectrum
from T0-0.128 to T0+2.688 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.97 +/- 0.01 and the cutoff energy,
parameterized as Epeak, is 2110 +/- 70 keV.
A Band function fits the spectrum equally well with Epeak = 2110 +/- 70 keV,
alpha = -0.97 +/- 0.01, and beta = -4 +/- 1.
The event fluence (10-1000 keV) in this time interval is
(2.80 +/- 0.02)E-05 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.77 s in the 10-1000 keV band is 154 +/- 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/"
GCN Circular 40708
Subject
GRB 250612C: SVOM/GRM observation an intermedium duration burst
Date
2025-06-12T16:01:33Z (5 months ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Ulysse Jacob (LUPM), Jean-Luc Atteia (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a bright burst GRB 250612C (SVOM trigger reference: sb25061214) at 2025-06-12T14:53:16.700 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40704).
The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. With the VHF data, the GRM light curve shows that this burst consists of a single spike with a T90 of 2.4 +/-0.8 s in the 15-5000 keV band. This burst is clearly detected in GRM VHF data beyond 550 keV, indicating a hard spectrum.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250612C.png
At the time of the burst, ECLAIRs was not taking data.
Refined analysis will be reported later.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)
GCN Circular 40706
Subject
GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
Date
2025-06-12T15:19:24Z (5 months ago)
From
Jochen Greiner at MPE <jcgrog@mpe.mpg.de>
Via
email
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
771432801 at 14:53:16 on 12 June 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) = 118.9 deg
Decl.(2000.0) = 18.8 deg
The 1 sigma statistical error radius is 1.1 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB250612620/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB250612620/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB250612620/json
GCN Circular 40704
Subject
GRB 250612C: Fermi GBM Final Real-time Localization
Date
2025-06-12T15:02:11Z (5 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 14:53:16 UT on 12 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250612C (trigger 771432801.582428 / 250612620).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 113.2, Dec = 16.2 (J2000 degrees, equivalent to J2000 07h 32m, 16d 11'), with a statistical uncertainty of 1.4 degrees.
The angle from the Fermi LAT boresight is 96.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250612620/quicklook/glg_skymap_all_bn250612620.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/bn250612620/quicklook/glg_healpix_all_bn250612620.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250612620/quicklook/glg_lc_medres34_bn250612620.gif