GRB 251028A
GCN Circular 42523
Subject
GRB 251028A: GECAM-B detection
Date
2025-10-30T15:46:39Z (16 hours ago)
Edited On
2025-10-30T22:42:01Z (9 hours ago)
From
guohx@ihep.ac.cn
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of guohx@ihep.ac.cn
Via
Web form
Hao-Xuan Guo, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by a long burst, GRB 251028A, at 2025-10-28T03:26:40.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42497, GCN#42499), MAXI/GSC (MAXI team, GCN#42498), Glowbug (C.C. Cheung et al., GCN#42506) and SVOM/GRM (SVOM/GRM team, SVOM/ECLAIRs team, GCN#42522).
According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 38 +4/-5 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb251028A.png
The time-averaged spectrum from T0-10 s to T0+45 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.05 +0.11/-0.11 and the cutoff energy, parameterized as Epeak, is 259 +38/-25 keV. The event fluence (10-1000 keV) in this time interval is (3.12 +0.20/-0.17)E-05 erg/cm^2. The 'Amati' relation diagram of GRB 251028A is shown at:
https://www.bursthub.cn//admin/static/gecambgrb251028A_amati.png
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).
GCN Circular 42522
Subject
GRB 251028A: SVOM/GRM observation
Date
2025-10-30T13:47:16Z (18 hours ago)
Edited On
2025-10-30T22:44:13Z (9 hours ago)
From
Haoxuan Guo <skyairsama@gmail.com>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of guohx@ihep.ac.cn
Via
Web form
SVOM/GRM team: Hao-Xuan Guo, Chen-Wei Wang, Zheng-Hang Yu, Chao Zheng, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)SVOM/ECLAIRs team: Report on behalf of the SVOM team:
SVOM/ECLAIRs team: Sebastien Guillot (IRAP)
SVOM/GRM was triggered in-flight by a burst GRB 251028A (SVOM trigger reference: sb25102801) at 2025-10-28T03:26:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42497, GCN#42499), MAXI/GSC (MAXI team, GCN#42498) and Glowbug (C.C. Cheung et al., GCN#42506).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple peaks with a T90 of 31.0 +6.5/-3.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb251028A.png
In addition, the position of this burst, as determined by Fermi/GBM (RA= 149.5, DEC= 20.2, GCN#42497), is located at about 157 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, but this burst still clearly detected by ECLAIRs due to the reflection of the Earth atmosphere.
With this localization, the time-averaged spectrum from T0-10 to T0+45 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.31 +0.14/-0.16 and the cutoff energy, parameterized as Epeak, is 345 +107/-64 keV. The event fluence (10-1000 keV) in this time interval is (4.56 +0.24/-0.27)E-5 erg/cm^2.
The localization of GRB 251028A in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb251028A_amati.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 point of contact for this burst is: Hao-Xuan Guo (IHEP)(guohx@ihep.ac.cn)
GCN Circular 42520
Subject
GRB 251028A: Fermi GBM Observation
Date
2025-10-29T20:08:12Z (a day ago)
From
Peter Veres at University of Alabama in Huntsville <veresp@gmail.com>
Via
Web form
P. Veres (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 03:26:31.86 UT on 28 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251028A (trigger 783314796/251028143) which was also detected by MAXI (Negoro et al. 2025, GCN 42498) and Glowbug (Cheung et al. 2025, GCN 42506). The Fermi GBM on-ground location is consistent with the MAXI position.
The angle from the Fermi LAT boresight is 50 degrees.
The GBM light curve consists of multiple overlapping pulses with a duration (T90)
of about 30 s (50-300 keV). The time-averaged spectrum
from T0 to T0+39.9 s is best fit by
a Band function with Epeak = 244 +/- 14 keV,
alpha = -0.91 +/- 0.03, and beta = -2.4 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is
(3.13 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+24 s in the 10-1000 keV band is 10.8 +/- 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/"
GCN Circular 42506
Subject
GRB 251028A: Glowbug gamma-ray detection
Date
2025-10-28T17:54:20Z (3 days ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 251028A, which was also detected by Fermi/GBM (GCN 42497, 42499) and MAXI/GSC (GCN 42498).
Using an adaptive window with a resolution of 32-ms, and taking the GBM-reported T0 (2025-10-28 03:26:31 UT), the burst onset is determined to be T0+22.48s with a duration of 2.0 s and a total significance of about 7.5 sigma. The single peak observed by Glowbug corresponds to the maximum in the Fermi/GBM light curve (GCN 42497). Additional lower-level emission from ~T0+5s to T0+20s may be present in the Glowbug light curve at low significance.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS, and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 42499
Subject
GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
Date
2025-10-28T04:28:32Z (3 days 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
783314796 at 03:26:31 on 28 Oct. 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) = 145.7 deg
Decl.(2000.0) = 16.8 deg
The 1 sigma statistical error radius is 2.1 deg.
We estimate an additional systematic error of 2 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB251028143/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB251028143/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB251028143/json
GCN Circular 42498
Subject
GRB 251028A: MAXI/GSC detection
Date
2025-10-28T04:17:17Z (3 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
H. Sugai (Chuo U.), Y. Kawakubo, M. Serino (AGU),
H. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.),
T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU),
Y. Tsuboi, N. Nagashima, Y. Ishihara (Chuo U.),
M. Shidatsu, C. Kang, T. Nakamoto (Ehime U.),
I. Takahashi, Y. Yatsu (Science Tokyo),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA),
Y. Ueda, K. Fujiwara (Kyoto U.),
M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (Kanazawa U.),
W. Iwakiri (Chiba U.),
T. Kawamuro (Osaka U.),
S. Yamada (Tohoku U)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at
03:27:06 UT on October 28, 2025.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (149.003 deg, 17.518 deg) = (09 56 00, +17 31 04) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.27 deg and 0.21 deg, respectively.
The roll angle of long axis from the north direction is 49.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 267 +- 43 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(148.423, 18.362) deg = (09 53 41, +18 21 43) (J2000)
(148.075, 17.954) deg = (09 52 17, +17 57 14) (J2000)
(149.164, 17.109) deg = (09 56 39, +17 06 32) (J2000)
(149.513, 17.514) deg = (09 58 03, +17 30 50) (J2000)
There was no significant excess flux in the previous transit at 02:15 UT
with an upper limit of 20 mCrab.
GCN Circular 42497
Subject
GRB 251028A: Fermi GBM Final Real-time Localization
Date
2025-10-28T03:36:52Z (3 days 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 03:26:31 UT on 28 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251028A (trigger 783314796.860488 / 251028143).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 149.5, Dec = 20.2 (J2000 degrees, equivalent to J2000 09h 58m, 20d 11'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 53.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251028143/quicklook/glg_skymap_all_bn251028143.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/bn251028143/quicklook/glg_healpix_all_bn251028143.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251028143/quicklook/glg_lc_medres34_bn251028143.gif