GRB 250117A
GCN Circular 39050
O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 20:21:57.89 UT on 17 January 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250117A (trigger 758838122/250117849).
which was also detected by Konus-Wind (Ridnaia et al. 2025, GCN 39001),
Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 38988), and SVOM/GRM (Wang et al. 2025, GCN 38994).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 252.55, Dec = -26.18 (J2000 degrees, equivalent to
J2000 20h 26m, +21d 13'), with a statistical uncertainty of 3.32 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).
The angle from the Fermi LAT boresight is 67 degrees.
An overwhelming volume of data produced by a contemporaneous solar flare
affected the spacecraft's ability to record data nominally, so TTE data was unavailable for this burst.
Consequently, the temporal and spectral analysis used the CTIME and CSPEC data types only.
The GBM light curve consists of one peak with a duration (T90)
of about 0.8 s (50-300 keV). The time-averaged spectrum
from T0+0.002 to T0+1.824 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.18 +/- 0.09 and the cutoff energy,
parameterized as Epeak, is 904 +/- 386 keV.
The event fluence (10-1000 keV) in this time interval is
(1.35 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.35 s in the 10-1000 keV band is 27 +/- 1 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 39001
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The short-duration GRB 250117A
(GECAM-B detection: Wang et al., GCN 38982;
Swift/BAT-GUANO localization: DeLaunay et al., GCN 38988;
SVOM/GRM detection: Wang et al., GCN 38994;
IPN triangulation: Ridnaia et al., GCN 39000)
triggered Konus-Wind at T0=73313.657 s UT (20:21:53.657).
The burst light curve shows a weak count rate increase (from
~T0-0.412 s to ~T0-0.288) followed by a bright, multi-peaked pulse,
which starts at ~T0-0.126 s and has a duration of ~0.138 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250117_T73313/
As observed by Konus-Wind, the burst had
the total fluence of 7.70(-0.02,+2.44)x10^-7 erg/cm^2
and a 16-ms peak flux, measured from T0-0.008 s,
of 1.87(-0.25,+0.64)x10^-5 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).
Since a major part of the burst emission
was detected before the trigger time, the spectral analysis
was performed using the KW 3-channel light curve data.
Modelling the KW 3-channel spectrum of the main pulse
(measured from T0-0.126 s to T0+0.012 s)
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = 0.52 (-0.54, + 0.75) and Ep = 459(-62,+84) keV.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 39000
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
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,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and
S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,
report:
The short-duration GRB 250117A
(GECAM-B detection: Wang et al., GCN 38982;
Swift/BAT-GUANO localization: DeLaunay et al., GCN 38988;
SVOM/GRM detection: Wang et al., GCN 38994)
was detected by Konus-Wind, Fermi (GBM),
INTEGRAL (SPI-ACS), Swift (BAT), GECAM-B,
and SVOM (GRM), at about 73318 s UT (20:21:58).
The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
249.314 (16h 37m 15s) -26.387 (-26d 23' 13")
Corners:
249.983 (16h 39m 56s) -33.454 (-33d 27' 16")
248.910 (16h 35m 38s) -28.572 (-28d 34' 20")
250.252 (16h 41m 01s) -19.117 (-19d 07' 02")
249.847 (16h 39m 23s) -24.228 (-24d 13' 41")
---------------------------------------------
The error box area is 5.4 sq. deg, and its maximum
dimension is 14.3 deg (the minimum one is 36 arcmin).
The Sun distance was 46 deg.
This localization may be improved.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250117_T73313/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 38994
SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
report on behalf of the SVOM team:
During the commissioning phase, SVOM/GRM was triggered in-flight by a short burst GRB 250117A (SVOM trigger reference: sb25011705) at 2025-01-17T20:21:58.300 UTC (T0), which was also detected by GECAM (GCN #38982), Swift/BAT (GCN #38988), Fermi/GBM, Konus-Wind and INTEGRAL/SPI-ACS.
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 0.91 +0.43/-0.28 s.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250117A.png
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/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang@ihep.ac.cn)
GCN Circular 38988
James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Gayathri Raman (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 250117A onboard (T0: 2025-11-17T20:21:57.89 UTC, Fermi trig 758838122, GECAM GCN 38982)
The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 17.2 in a 0.128 s analysis time bin, starting at T0 + 0.288 s.
Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep)
The 90% credible area is 2,585 deg2 and the 50% credible area is 143 deg2. The integrated probability inside the coded field of view is <1%.
The NITRATES skymap is consistent with the Fermi localization reported in the final position notice and the GECAM-B localization (GCN 38982).
A plot of the probability skymap can be viewed here:
The probability skymap file can be downloaded from the link here
Instructions on how to read and manipulate this map can be found here:
https://guano.swift.psu.edu/documentation
More details about this burst can be found on the trigger report page here:
https://guano.swift.psu.edu/trigger_report?id=758838152
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
GCN Circular 38982
Chen-Wei Wang, Yan-Qiu Zhang, Jin-Peng Zhang, Shao-Lin Xiong (IHEP)
report on behalf of GECAM team:
GECAM-B was triggered in-flight by a short burst, GRB 250117A, at 2025-01-17T20:21:57.950 UTC (denoted as T0), which was also detected by Fermi/GBM, Konus-Wind and INTEGRAL/SPI-ACS.
According to the GECAM-B light curves in about 20-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 0.70 +0.25/-0.65 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecamgrb250117A.png
Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000):
Ra: 271.8 deg
Dec: -23.2 deg
Err: 7.6 deg (1-sigma, statistical only)
We note that GRB 250117A is located near the galactic disc, and its localization seems to be consistent with the position of GRB 250116A (Ra= 266.64 deg，Dec=-19.36 deg, Err=0.13 deg, GCN # 38963) within the error, which may suggest that both bursts possibly come from ssan interesting galactic source. More analysis is ongoing.
Follow-up observations of GRB 250117A and GRB 250116A are encouraged.
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).