GRB 251105A
GCN Circular 42596
O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 04:41:06.40 UT on 05 November 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251105A (trigger 784010471/251105195)
which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 42593).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 41 degrees.
The GBM light curve consists of one emission episode with a duration (T90)
of about 65 s (50-300 keV). The time-averaged spectrum
from T0-23 to T0+87 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.13 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 220 +/- 30 keV.
A Band function fits the spectrum equally well
with Epeak= 190 +/- 30 keV, alpha = -1.08 +/- 0.08 and beta = -2.38 +/- 0.39.
The event fluence (10-1000 keV) in this time interval is
(1.26 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.8 s in the 10-1000 keV band is 3.2 +/- 0.2 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 42593
James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report:
Swift/BAT did not localize GRB 251105A onboard (T0: 2025-11-05T04:41:06.40 UTC, Fermi Trig 784010471)
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 22.9 in a 16.384 s analysis time bin, starting at T0 + 4.096 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 747 deg2 and the 50% credible area is 279 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 (GCN 42584). The combined Fermi/GBM+NITRATES 90% credible area is 129 deg2 and the 50% credible area is 35 deg2.
A plot of the probability skymap can be viewed here:
The probability skymap and joint skymap files can be downloaded from the links 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=784010503
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 42585
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 251105A ( Fermi GBM team, GCN 42584) errorbox 129 sec after notice time and 150 sec after trigger time at 2025-11-05 04:43:37 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 43 deg. The sun altitude is -43.0 deg.
The galactic latitude b = -25 deg., longitude l = 190 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3033298
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
166 | 2025-11-05 04:43:37 | MASTER-OAFA | (04h 39m 45.81s , +05d 19m 45.6s) | C | 30 | 17.7 |
207 | 2025-11-05 04:44:13 | MASTER-OAFA | (04h 39m 45.84s , +05d 19m 46.9s) | C | 40 | 17.9 |
258 | 2025-11-05 04:44:59 | MASTER-OAFA | (04h 39m 45.88s , +05d 19m 48.6s) | C | 50 | 18.1 |
319 | 2025-11-05 04:45:55 | MASTER-OAFA | (04h 39m 45.91s , +05d 19m 50.3s) | C | 60 | 18.0 |
390 | 2025-11-05 04:47:01 | MASTER-OAFA | (04h 39m 45.96s , +05d 19m 52.4s) | C | 70 | 18.1 |
957 | 2025-11-05 04:56:33 | MASTER-OAFA | (04h 38m 41.39s , +07d 10m 46.5s) | C | 60 | 18.2 |
1023 | 2025-11-05 04:57:38 | MASTER-OAFA | (04h 38m 41.37s , +07d 10m 48.1s) | C | 60 | 18.3 |
1088 | 2025-11-05 04:58:44 | MASTER-OAFA | (04h 38m 41.40s , +07d 10m 49.8s) | C | 60 | 18.3 |
1154 | 2025-11-05 04:59:50 | MASTER-OAFA | (04h 38m 41.39s , +07d 10m 51.5s) | C | 60 | 18.3 |
1219 | 2025-11-05 05:00:55 | MASTER-OAFA | (04h 38m 41.39s , +07d 10m 53.2s) | C | 60 | 18.3 |
1285 | 2025-11-05 05:02:01 | MASTER-OAFA | (04h 38m 41.39s , +07d 10m 54.7s) | C | 60 | 18.3 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 42584
The Fermi GBM team reports the detection of a likely LONG GRB
At 04:41:06 UT on 5 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251105A (trigger 784010471.401264 / 251105195).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 69.6, Dec = 7.1 (J2000 degrees, equivalent to J2000 04h 38m, 7d 05'), with a statistical uncertainty of 3.3 degrees.
The angle from the Fermi LAT boresight is 41.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251105195/quicklook/glg_skymap_all_bn251105195.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/bn251105195/quicklook/glg_healpix_all_bn251105195.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251105195/quicklook/glg_lc_medres34_bn251105195.gif