GRB 260127B
GCN Circular 43701
Subject
Konus-Wind detection of GRB 260127B
Date
2026-02-11T17:39:39Z (2 months ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,
A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB 260127B
(Fermi-GBM detection: The Fermi GBM team, GCN 43533;
Trigg, GCN 43573;
IPN triangulation: Ridnaia et al., GCN 43559;
AstroSat-CZTI detection: ,GCN 43576;
GECAM-B observation: Ren et al., GCN 43597;
Insight-HXMT/HE detection: Ren et al., GCN 43598)
triggered Konus-Wind at T0=72154.163 s UT (20:02:34.163).
The burst light curve shows a multipeaked structure,
which starts at ~T0-0.1 s and has a total duration of ~0.3 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260127_T72154/
As observed by Konus-Wind, the burst
had a fluence of 2.09(-0.27,+0.38)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.062 s,
of 1.80(-0.40,+0.51)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 1.3 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.21(-0.27,+0.31)
and Ep = 796(-151,+261) keV (chi2 = 24/25 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.
GCN Circular 43598
Subject
GRB 260127B: Insight-HXMT/HE detection
Date
2026-02-02T03:28:19Z (2 months 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 2026-01-27T20:02:32.500 (T0), Insight-HXMT/HE detected a short burst, GRB 260127B, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43533), AstroSat/CZTI (Arya et al., GCN #43576), and GECAM-B (Ren et al., GCN #43597).
The Insight-HXMT/HE light curve mainly consists of multi-pulses with T90 of 0.17 +0.04/-0.02 s. The 1s peak rate, measured from T0+0.01 s, is 2733 cnts/sec. Insight-HXMT/HE detected a total of 2735 counts from this burst.
The Insight-HXMT /HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260127B.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://hxmten.ihep.ac.cn/
GCN Circular 43597
Subject
GRB 260127B: GECAM-B observation of a short burst
Date
2026-02-02T03:20:39Z (2 months ago)
From
renyz16607@163.com
Via
Web form
Yang-Zhao Ren, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 260127B, at 2026-01-27T20:02:32.650 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43533), and AstroSat/CZTI (Arya et al., GCN #43576).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 0.13 +0.11/-0.02 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260127B.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 43576
Subject
GRB 260127B: AstroSat CZTI detection
Date
2026-01-31T05:11:40Z (2 months ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), 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 short GRB 260127B which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43533), Swift BAT (Evans et al., GCN Circ. 43542), and Konus IPN (Ridnaia et al., GCN Circ. 43559).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-01-27 20:02:32.605 UTC. The measured peak count rate associated with the burst is 2558 (+901, -550) counts/s above the background in the combined data of all quadrants, with a total of 233 (+42, -31) counts. The local mean background count rate was 261 (+9, -32) counts/s. Using cumulative rates, we measure a T90 of 0.17 (+0.11, -0.03) s.
The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-01-27 20:02:32.292 UTC. The measured peak count rate associated with the burst is 602 (+68, -74) counts/s above the background in the combined data of all quadrants, with a total of 604 (+160, -170) counts. The local mean background count rate was 1239 (+7, -8) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 for our detection.
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 43573
Subject
GRB 260127B: Fermi GBM Detection
Date
2026-01-30T21:27:55Z (2 months ago)
From
atrigg2@lsu.edu
Via
Web form
A. C. Trigg (NPP ORAU, NASA MSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 20:02:32.57 UT on 27 January 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260127B (trigger 791236957/260127835).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 190.42, Dec = 56.88 (J2000 degrees, equivalent to
J2000 12h 41m, +56d 52'), with a statistical uncertainty of 5.21 degrees.
(radius, 1-sigma containment, statistical only; there is additionally a
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).
The angle from the Fermi LAT boresight is 109 degrees.
The GBM light curve displays a single short peak with a duration (T90)
of about 1 s (50-300 keV). The time-averaged spectrum
from T0-0.1 to T0+0.3 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.11 +/- 0.01 and the cutoff energy,
parameterized as Epeak, is 710 +/- 30 keV.
The event fluence (10-1000 keV) in this time interval is
(1.29 +/- 0.09)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.064 s in the 10-1000 keV band is 22 +/- 2 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 570 +/- 20 keV, alpha = -0.040 +/- 0.002 and beta = -2 +/- 0.1.
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 43559
Subject
IPN triangulation of GRB 260127B (short)
Date
2026-01-29T18:13:36Z (2 months ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
and T. Cline on behalf of the Konus-Wind team,
and
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
report:
The short-duration GRB 260127B
(Fermi-GBM detection: The Fermi GBM team, GCN 43533)
was detected by Fermi (GBM trigger 791236957) and Konus-Wind
at about 72153 s UT (20:02:33).
We have triangulated it to a Konus-GBM annulus centered at
RA(2000)=104.669 deg (06h 58m 40s) Dec(2000)=+21.845 deg (+21d 50' 41"),
whose radius is 72.490 +/- 0.104 deg (3 sigma).
The annulus combined with the Fermi-GBM final position (GCN 43533;
glg_healpix_all_bn260127835_v00) gives ~6.8 sq. deg (3 sigma) localization region.
The the optical source detected by GOTO (GOTO26aih/AT2026bnn, GCN 43538)
is outside the IPN annulus.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB260127_T72154/IPN/
GCN Circular 43558
Subject
GRB 260127B: Swift-XRT observations
Date
2026-01-29T15:59:58Z (2 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), S. Campana (INAF-OAB), A.
Melandri (INAF-OAR), T. Sbarrato (INAF-OAB) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/GBM-detected burst GRB 260127B (The Fermi GBM team, GCN Circ.
43533), collecting 985 s of Photon Counting (PC) mode data between
T0+70.4 ks and T0+71.4 ks.
No X-ray sources have been detected consistent with the tentative GOTO
optical afterglow candidate (O’Neill et al, GCN Circ. 43538). The
3-sigma upper limit in the field ranges from ~0.01 to ~0.02 ct s^-1,
corresponding to a 0.3-10 keV observed flux of 5.0e-13 to 6.9e-13 erg
cm^-2 s^-1 (assuming a typical GRB spectrum).
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021900.
This circular is an official product of the Swift-XRT team.
GCN Circular 43542
Subject
GRB 260127B: Swift ToO observations
Date
2026-01-28T15:34:04Z (2 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/GBM-detected event
GRB 260127B. Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021900
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/GBM event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 43538
Subject
GRB 260127B: GOTO candidate optical counterpart
Date
2026-01-28T10:22:31Z (2 months ago)
Edited On
2026-01-28T14:54:25Z (2 months ago)
From
d.s.oneill@bham.ac.uk
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of d.s.oneill@bham.ac.uk
Via
Web form
D. O’Neill, B. P. Gompertz, G. Ramsay, M. Kennedy, D. Steeghs, J. Lyman, R. Starling, K. Ackley, M. Dyer, K. Ulaczyk, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, M. Pursiainen report on behalf of GOTO collaboration:
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the short GRB 260127B (Fermi GBM Team, GCN 43533).
Observations covering the localisation area began at 2026-01-28 00:20:53 UT (+4.31h post trigger) and continued through to 2026-01-28 05:10:59 (+9.14h post trigger). 141 images were taken, across 9 unique pointings, covering 242.7 square degrees within the 90% localisation contour. ~61.4% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.2 mag.
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks.
We identify one candidate optical counterpart, GOTO26aih (AT2026bnn), within the 90% probability contour at coordinates RA = 12:49:52.73, Dec = +66:44:58.87, equivalent to RA = 192.469711, Dec =66.74969 degrees. This position lies on the 84th percentile probability contour of the Fermi/GBM localisation map.
The source was initially detected with L = 19.15 ± 0.14 AB mag (t0+5.66h), before fading to L = 19.82 ± 0.11 mag (t0+7.91h). The measured rate of decay is t^-1.66 ± 0.97. We find no evidence of the source prior to the GRB trigger time in the most recent GOTO observations taken at 2026-01-20 06:01:17 (t0-7.6 days) down to a 5-sigma depth of >20.8 AB mag. We also find no evidence for pre-GRB emission in the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021).
GOTO26aih/AT2026bnn is spatially coincident with the galaxy SDSS J124952.79+664500.4, offset by 1.5” from the core. This galaxy has a measured spectroscopic redshift of z = 0.12 (DESI Collaboration, 2025).
A summary of our observations is presented below.
+------------------------------------------------------------+
| Observation time (UT) | t-t0 | filter | mag |
+------------------------------------------------------------+
| 2026-01-20 06:37:17 | -181.42h | L | >20.8 |
| 2026-01-28 01:42:13 | +5.66h | L | 19.15 ± 0.14 |
| 2026-01-28 02:49:23 | +6.78h | L | 19.79 ± 0.14 |
| 2026-01-28 03:57:22 | +7.91h | L | 19.82 ± 0.11 |
+-------------------------------------------------------------+
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 43534
Subject
Fermi GRB 260127B: Global MASTER-Net observations report
Date
2026-01-27T21:30:30Z (2 months 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260127B ( Fermi GBM team, GCN 43533) errorbox 2657 sec after notice time and 2678 sec after trigger time at 2026-01-27 20:47:11 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 7 deg. The sun altitude is -37.8 deg.
The galactic latitude b = 60 deg., longitude l = 125 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3117123
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
2709 | 2026-01-27 20:47:11 | MASTER-Tunka | (12h 37m 21.08s , +57d 00m 17.6s) | C | 60 | 19.5 |
2822 | 2026-01-27 20:49:04 | MASTER-Tunka | (12h 51m 46.69s , +57d 02m 10.2s) | C | 60 | 19.7 |
2897 | 2026-01-27 20:50:19 | MASTER-Tunka | (12h 19m 40.16s , +58d 55m 09.9s) | C | 60 | 19.7 |
2970 | 2026-01-27 20:51:32 | MASTER-Tunka | (12h 34m 49.83s , +58d 54m 52.1s) | C | 60 | 19.7 |
3049 | 2026-01-27 20:52:51 | MASTER-Tunka | (12h 27m 48.95s , +55d 06m 33.8s) | C | 60 | 19.7 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html
GCN Circular 43533
Subject
GRB 260127B: Fermi GBM Final Real-time Localization
Date
2026-01-27T20:13:04Z (2 months 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 SHORT GRB
At 20:02:32 UT on 27 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127B (trigger 791236957.568148 / 260127835).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 190.4, Dec = 56.9 (J2000 degrees, equivalent to J2000 12h 41m, 56d 53'), with a statistical uncertainty of 5.2 degrees.
The angle from the Fermi LAT boresight is 109.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/quicklook/glg_skymap_all_bn260127835.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/quicklook/glg_healpix_all_bn260127835.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127835/quicklook/glg_lc_medres34_bn260127835.gif