GRB 251006A
GCN Circular 42144
James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report:
Swift/BAT did not localize GRB 251006A onboard (T0: 2025-10-06T13:27:35.03 UTC, Fermi/GBM trig 781450060, Glowbug GCN 42130)
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 7.1 in a 0.256 s analysis time bin, starting at T0 - 0.064 s. This corresponds to a FAR ~ 9e-4 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 16,319 deg2 and the 50% credible area is 6,346 deg2. The integrated probability inside the coded field of view is 5%.
The NITRATES skymap is very large but is consistent with the Fermi localization reported in the final position notice (GCN 42124).
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=781450091
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 42130
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 251006A, which was also detected by Fermi/GBM (GCN 42124).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-06 13:27:33.944 with a duration of 0.26 s and a total significance of about 18.8 sigma. The light curve comprises a single peak with possible substructure.
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 42128
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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251006A ( Fermi GBM team, GCN 42124) errorbox 16713 sec after notice time and 16748 sec after trigger time at 2025-10-06 18:06:43 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 42 deg. The sun altitude is -18.0 deg.
The galactic latitude b = 4 deg., longitude l = 12 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3008484
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
16778 | 2025-10-06 18:06:43 | MASTER-SAAO | (17h 34m 02.34s , -16d 58m 33.7s) | C | 60 | 16.7 |
16778 | 2025-10-06 18:06:43 | MASTER-SAAO | (17h 32m 04.73s , -16d 43m 22.6s) | C | 60 | 16.8 |
16871 | 2025-10-06 18:08:16 | MASTER-SAAO | (17h 40m 13.62s , -14d 06m 21.6s) | C | 60 | 16.9 |
16871 | 2025-10-06 18:08:16 | MASTER-SAAO | (17h 38m 17.54s , -13d 51m 10.9s) | C | 60 | 17.0 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 42124
The Fermi GBM team reports the detection of a likely SHORT GRB
At 13:27:35 UT on 6 Oct 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251006A (trigger 781450060.028394 / 251006561).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 269.1, Dec = -16.6 (J2000 degrees, equivalent to J2000 17h 56m, -16d 36'), with a statistical uncertainty of 12.0 degrees.
The angle from the Fermi LAT boresight is 30.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251006561/quicklook/glg_skymap_all_bn251006561.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/bn251006561/quicklook/glg_healpix_all_bn251006561.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251006561/quicklook/glg_lc_medres34_bn251006561.gif