GRB 251007A
GCN Circular 42167
Subject
GRB 251007A: AstroSat CZTI detection
Date
2025-10-08T12:42:43Z (17 hours ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), U. Pathak (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 a long-duration GRB 251007A which was also detected by Swift/BAT (GCN Circ. 42146), Glowbug (GCN Circ. 42151) and Calet GBM (GCN Circ. 42156).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-10-07 19:37:51.50 UTC. The measured peak count rate associated with the burst is 579 (+44, -41) counts/s above the background in the combined data three quadrants out of four, with a total of 4746 (+253, -236) counts. The local mean background count rate was 186 (+1, -2) counts/s. Using cumulative rates, we measure a T90 of 17.5 (+4.1, -1.3) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-10-07 19:37:49.6 UTC. The measured peak count rate associated with the burst is 1557 (+83, -88) counts/s above the background in the combined data of all quadrants, with a total of 9759 (+524, -526) counts. The local mean background count rate was 1146 (+3, -4) counts/s. We measure a T90 of 16.9 (+6.6, -1.3) s from the cumulative Veto light curve.
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 42162
Subject
GRB 251007A: Swift-XRT refined Analysis
Date
2025-10-08T08:34:11Z (21 hours ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio
(INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU),
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans
report on behalf of the Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 251007A, from 58 s to 39.2
ks after the trigger. The data comprise 362 s in Windowed Timing (WT)
mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+11.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.46 (+/-0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.92 (+/-0.04). The
best-fitting absorption column is 1.79 (+0.15, -0.14) x 10^21 cm^-2,
in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.82 (+/-0.12) and a
best-fitting absorption column of 1.6 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.6 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.0 x 10^20 cm^-2
Excess significance: 5.1 sigma
Photon index: 1.82 (+/-0.12)
If the light curve continues to decay with a power-law decay index of
1.46, the count rate at T+24 hours will be 0.052 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x
10^-12 (2.5 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01402466.
This circular is an official product of the Swift-XRT team.
GCN Circular 42161
Subject
GRB 251007A: Enhanced Swift-XRT position
Date
2025-10-08T08:06:25Z (21 hours ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1898 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 251007A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 128.17650, +21.81297 which is equivalent
to:
RA (J2000): 08h 32m 42.36s
Dec (J2000): +21d 48' 46.7"
with an uncertainty of 2.0 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 42158
Subject
GRB 251007A: NOT optical observations
Date
2025-10-08T06:46:01Z (a day ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), T. Pursimo (NOT), A. L. Bouquin (NOT and DTU Space) report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 251007A (Ambrosi et al., GCN 42146; Wu et al., GCN 42154) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started on 2025 Oct 8.16 UT (8.2 hr after the trigger), as soon as the target was visible from La Palma, and consisted of images in the SDSS g, r, and i filters.
In a stack of nine 200 s images, we measure
i = 21.07 +- 0.07
at a mean epoch of 2025 Oct 8.17 UT (8.46 hr after the trigger). This magnitude is in the AB system, is calibrated against nearby stars from the Pan-STARRS catalog, and is not corrected for Galactic extinction.
The afterglow looks red, with a color r-i ~ 0.4, which corresponds to a spectral slope alpha ~ 1.9 (F_nu propto nu^-alpha). This is consistent with the bright i-band detection by SVOM/C-GFT (Wu et al., GCN 42154).
GCN Circular 42157
Subject
GRB 251007A: AKO Optical Upper Limit
Date
2025-10-08T05:50:58Z (a day ago)
From
Mohammad Odeh at Al Khatim Observatory M44 <mshodeh@gmail.com>
Via
email
Mohammad Odeh (Al-Khatim Observatory - AKO, operated by the International
Astronomical Center in Abu Dhabi, UAE), Nidhal Guessoum (American University
of Sharjah, UAE), and Shaikha Alshamsi (University of Sharjah, UAE), report:
We observed the field of GRB 251007A detected by Swift/BAT (Ambrosi et al.,
GCN 42146) and Glowbug (Cheung et al., GCN 42151), using our 0.36m f/7.7
robotic telescope. The observation session began on 07 October 2025 at 23:03
UT, with a midpoint at 23:45 UT, approximately 4.1 hours after the trigger.
We did not detect any uncatalogued source down to Ic=17.8 (5-sigma), not
corrected for galactic extinction, at the position reported by Swift/UVOT
(Ambrosi et al., GCN 42146).
GCN Circular 42156
Subject
GRB 251007A: CALET Gamma-Ray Burst Monitor detection
Date
2025-10-08T05:38:59Z (a day ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (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 251007A (Swift detection: Ambrosi et al., GCN Circ. 42146;
Glowbug gamma-ray detection: Cheung et al., GCN Circ. 42151) triggered
the CALET Gamma-ray Burst Monitor (CGBM) at 19:37:48.18 UTC on 7 October 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1443900615/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure that starts
at T+3.0 sec, peaks at T+6.3 sec, and ends at T+21.9 sec.
The T90 and T50 durations measured by the SGM data are 15.7 +/- 0.3 sec
and 9.2 +/- 0.3 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1443900615/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 42154
Subject
GRB 251007A: SVOM/C-GFT optical observations
Date
2025-10-07T23:55:44Z (a day ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 251007A detected by Swift/BAT (Ambrosi et al., GCN 42146) and Glowbug (Cheung et al., GCN 42151) with LATIOS on SVOM/C-GFT. Observations started at 2025-10-07T19:37:48 UTC, ~50 seconds after the trigger.
The optical counterpart reported by Swift/UVOT (Ambrosi et al., GCN 42146) is clearly detected in our i-band images. The magnitude is :
|[date-obs|mid-time] | Mid_t-T0(s) | exposure time (s) | band | mag (AB) | mag_err |
|---------------------|-------------|-------------------|------|----------|---------|
| 2025-10-07T19:37:53 | 55 | 10 | i | 16.41 | 0.13 |
The photometry was calibrated against the UCAC4 catalogue, and no correction for Galactic dust extinction was applied.
We thank the observation assistants Chunlei Guo and Shuai Liu at Jilin observatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
GCN Circular 42151
Subject
GRB 251007A: Glowbug gamma-ray detection
Date
2025-10-07T22:35:45Z (a day 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 251007A, which was also detected by Swift/BAT (GCN 42146) and CALET (Trigger 1443900615).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-07 19:37:09.088 with a duration of 65.5 s and a total significance of about 137.8 sigma. The Glowbug light curve is dominated by a triple-peaked structure spanning ~ T0+40s to +60s corresponding to the peak emission observed by Swift/BAT and CALET.
Note the Glowbug onset time is ~11 s after the Swift/BAT trigger time (19:36:58). A search of the Glowbug data for emission at the Swift/BAT T0 was inconclusive.
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 recently 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 42149
Subject
Swift GRB 251007A: Global MASTER-Net observations report
Date
2025-10-07T21:52:44Z (a day ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 251007A ( E. Ambrosi et al., GCN 42146) errorbox 7658 sec after notice time and 7679 sec after trigger time at 2025-10-07 21:44:57 UT, with upper limit up to 15.8 mag. The observations began at zenith distance = 84 deg. The sun altitude is -51.3 deg.
The galactic latitude b = 32 deg., longitude l = 203 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3009554
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
7770 | MASTER-Kislovodsk | C | 180 | 15.8 |
7770 | MASTER-Kislovodsk | C | 180 | 14.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 42146
Subject
GRB 251007A: Swift detection of a burst with an optical counterpart
Date
2025-10-07T19:53:26Z (a day ago)
From
David Palmer at LANL <palmer@lanl.gov>
Via
email
E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), R. Gupta (NASA GSFC),
N. J. Klingler (GSFC/UMBC/CRESSTII), N. P. M. Kuin (UCL-MSSL),
A. Melandri (INAF-OAR), M. J. Moss (GSFC), K. L. Page (U Leicester)
and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 19:36:58 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 251007A (trigger=1402466). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 128.173, +21.823 which is
RA(J2000) = 08h 32m 42s
Dec(J2000) = +21d 49' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with an initial sequence of peaks followed by a larger
complex peak with a total duration of about 100 sec. The peak count rate
was ~12000 counts/sec (15-350 keV), at ~56 sec after the trigger.
The XRT began observing the field at 19:38:07.4 UT, 69.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 128.1775, 21.8138 which is equivalent to:
RA(J2000) = 08h 32m 42.60s
Dec(J2000) = +21d 48' 49.7"
with an uncertainty of 5.4 arcseconds (radius, 90% containment). This
location is 36 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 78 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 08:32:42.40 = 128.17665
DEC(J2000) = +21:48:46.1 = 21.81280
with a 90%-confidence error radius of about 0.63 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.38 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.039.
Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)