GRB 251105B
GCN Circular 42634
Subject
GRB 251105B: Insight-HXMT/HE detection
Date
2025-11-10T08:51:03Z (a year ago)
From
renyz16607@163.com
Via
Web form
Yang-Zhao Ren, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team:
At 2025-11-05T00:58:34.700 (T0), Insight-HXMT/HE detected a short-duration GRB with extended emission, GRB 251105B, which is also detected by SVOM/GRM (Wang et al., GCN#42586), Fermi/GBM (Fermi GBM team, GCN #42589), and AstroSat/CZTI (Harsha et al., GCN#42591).
The Insight-HXMT/HE light curve mainly consists of a narrow, hard spike followed by a long pulse with a T90 of 39.7 +7.9/-2.1 s. The 1s peak rate, measured from T0-0.34 s, is 2439 cnts/sec. Insight-HXMT/HE detected a total of 22413 counts from this burst.
The Insight-HXMT /HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb251105B.png
All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org
GCN Circular 42614
Subject
IPN triangulation of GRB 251105B (possible sGRB with EE)
Date
2025-11-07T15:12:08Z (a year ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the HEND/Mars Odyssey team,
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
and T. Cline on behalf of the Konus-Wind team,
Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier
on behalf of the SVOM-GRM team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:
The possible short-duration GRB with extended emission GRB 251105B
(SVOM-GRM detection: Wang et al., GCN 42586;
Fermi-GBM detection: Hamburg eat al., GCN 42589;
AstroSat-CZTI detection: Harsha et al., GCN 42591)
was detected by SVOM (GRM), Konus-Wind, Fermi (GBM), AstroSat (CZTI),
and Mars-Odyssey (HEND) at about 3514 s UT (00:58:34).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
277.814 (18h 31m 15s) +9.028 ( +9d 01' 39")
Corners:
277.022 (18h 28m 05s) +9.993 ( +9d 59' 36")
277.294 (18h 29m 11s) +9.729 ( +9d 43' 46")
278.607 (18h 34m 26s) +8.012 ( +8d 00' 43")
278.333 (18h 33m 20s) +8.303 ( +8d 18' 10")
---------------------------------------------
The error box area is 362 sq. arcmin, and its maximum
dimension is 2.5 deg (the minimum one is 3 arcmin).
The Sun distance was 62 deg.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB251105_T03511/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 42591
Subject
GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
Date
2025-11-05T18:10:53Z (a year ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 251105B which was also detected by SVOM/GRM (Wang et. al., GCN Circ. 42586), Fermi/GBM (Hamburg et. al., GCN Circ. 42589) and Konus-Wind (IPN notices).
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve shows an initial short-duration burst followed by an extended emission which peaks at 2025-11-05 00:58:56.35 UTC. The measured peak count rate associated with the burst is 253 (+94, -8) counts/s above the background in the combined data of all quadrants, with a total of 2711 (+723, -732) counts. The local mean background count rate was 1840 (+6, -6) counts/s. We measure a T90 of 24 (+11, -9) s from the cumulative Veto light curve for the entire burst.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 42589
Subject
Fermi GBM Sub-Threshold Detection of GRB 251105B
Date
2025-11-05T16:40:32Z (a year ago)
From
rhamburg@usra.edu
Via
Web form
R. Hamburg (USRA), P. Veres (UAH), E. Burns (LSU) report on behalf of the Fermi-GBM Team:
The SVOM/GRM detected GRB 251105B on 2025-11-05 at 00:58:34.700 UTC (Wang et al 2025, GCN 42586). There was an unrelated Fermi-GBM trigger approximately 2 minutes before this time, which disabled the onboarding triggering for 10 min.
The GBM Targeted Search [1], the most sensitive coherent search for short GRB signals in GBM, identified a GRB-like transient starting 0.128 seconds after the SVOM/GRM time, most significantly on the 0.256 s timescale with a "hard" GRB spectrum (i.e., Comptonized function with Epeak = 1500 keV, alpha = -0.5) and an SNR of 60.9. The GRB lightcurve consists of a bright, short peak about 0.5 s in duration seen up to ~1 MeV followed by a period of extended emission out to ~60 s. The Targeted Search localization is RA=279.5 deg, Dec=3.6 deg, with an error of 14.3 deg. (90% CI).
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular 42586
Subject
GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
Date
2025-11-05T13:22:13Z (a year 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: Marius Brunet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a burst GRB 251105B (SVOM trigger reference: sb25110501) at 2025-11-05T00:58:34.700 UTC (T0).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow hard spike followed by a FRED shape long pulse with a T90 of 43.6 +6.0/-5.4 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb251105B.png
ECLAIRs was collecting data at the time of this burst but no signal was detected, suggesting the burst localized outside ECLAIRs FoV.
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)