GRB 260512A
GCN Circular 44617
Subject
Konus-Wind detection of GRB 260512A
Date
2026-05-15T10:45:03Z (13 days ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
Via
Web form
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long-duration GRB 260512A
(Fermi-GBM detection: The Fermi GBM team, GCN 44587;
NuSTAR-ACS detection: Waratkar et al., GCN 44591;
AstroSat-CZTI detection: Tembhurnikar et al., GCN 44608;
IPN triangulation: Kozyrev et al., GCN 44611)
triggered Konus-Wind at T0=61005.883 s UT (16:56:45.883).
The burst light curve shows a multipeaked structure
which starts at ~T0-0.7 s and has a total duration of ~23 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260512_T61005/
As observed by Konus-Wind, the burst
had the total fluence of 2.45(-0.24,+0.20)x10^-5 erg/cm2,
and the 64-ms peak flux, measured from T0+4.464 s,
of 6.32(-0.82,+0.83)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+24.832 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.99(-0.09,+0.09),
the high energy photon index beta = -2.60(-0.46,+0.17),
the peak energy Ep = 202(-16,+22) keV
(chi2 = 117/98 dof).
The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.82(-0.08,+0.08),
the high energy photon index beta = -2.53(-0.13,+0.10),
the peak energy Ep = 193(-11,+13) keV
(chi2 = 93/79 dof).
All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.
GCN Circular 44611
Subject
IPN triangulation of GRB 260512A
Date
2026-05-14T15:55:38Z (13 days ago)
From
Dmitry Svinkin at Ioffe Institute <dmitrysvinkin@gmail.com>
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,
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 long-duration GRB 260512A
(Ferm-GBM detection: The Fermi GBM team, GCN 44587;
NuSTAR-ACS detection: Waratkar et al., GCN 44591;
AstroSat-CZTI detection: Tembhurnikar et al., GCN 44608)
was detected by Fermi (GBM trigger 800297808),
Konus-Wind, NuSTAR (ACS), AstroSat (CZTI), and Mars-Odyssey (HEND)
at about 61003 s UT (16:56:43).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
131.305 (08h 45m 13s) -83.033 (-83d 02' 00")
Corners:
128.432 (08h 33m 44s) -81.525 (-81d 31' 31")
128.203 (08h 32m 49s) -81.573 (-81d 34' 22")
135.825 (09h 03m 18s) -84.513 (-84d 30' 48")
136.100 (09h 04m 24s) -84.461 (-84d 27' 41")
---------------------------------------------
The error box area is 485 sq. arcmin, and its maximum
dimension is 3.1 deg (the minimum one is 2.6 arcmin).
The Sun distance was 106 deg.
This localization may be improved.
A triangulation map and HEALPix FITS files are posted at
http://www.ioffe.ru/LEA/GRBs/GRB260512_T61005/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 44608
Subject
GRB 260512A: AstroSat CZTI detection
Date
2026-05-14T10:11:36Z (14 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (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 GRB 260512A which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44587), and NuSTAR (Waratkar et. al. , GCN Circ. 44591).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-05-12 16:56:47.5 UTC. The measured peak count rate associated with the burst is 302 (+33, -31) counts/s above the background in the combined data of two quadrants (out of four), with a total of 1755 (+142, -215) counts. The local mean background count rate was 159 (+2, -5) counts/s. We measure a T90 of 13 (+1, -1) s from the cumulative CZT light curve.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-05-12 16:56:46.4 UTC. The measured peak count rate associated with the burst is 655 (+88, -70) counts/s above the background in the combined data of all quadrants, with a total of 3682 (+588, -378) counts.The local mean background count rate was 1822 (+7, -14) counts/s. We measure a T90 of 10 (+2, -2) 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 44601
Subject
Fermi GRB 260512A: Global MASTER-Net observations report
Date
2026-05-14T00:15:51Z (14 days 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260512A ( Fermi GBM team, GCN 44587) errorbox 1 days 24421 sec after notice time and 1 days 24449 sec after trigger time at 2026-05-13 23:44:12 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 51 deg. The sun altitude is -24.8 deg.
The galactic latitude b = -22 deg., longitude l = 298 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3309891
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
110879 | 2026-05-13 23:44:12 | MASTER-OAFA | (10h 10m 53.82s , -82d 11m 47.5s) | C | 60 | 19.7 |
110939 | 2026-05-13 23:44:12 | MASTER-OAFA | (10h 10m 53.83s , -82d 11m 47.6s) | C | 180 | 19.9 | Coadd
110955 | 2026-05-13 23:45:28 | MASTER-OAFA | (10h 11m 00.56s , -82d 09m 55.3s) | C | 60 | 19.7 |
111036 | 2026-05-13 23:46:49 | MASTER-OAFA | (10h 10m 53.19s , -82d 10m 52.8s) | C | 60 | 19.6 |
111114 | 2026-05-13 23:48:07 | MASTER-OAFA | (10h 10m 56.57s , -82d 09m 54.2s) | C | 60 | 19.6 |
111174 | 2026-05-13 23:48:07 | MASTER-OAFA | (10h 10m 56.60s , -82d 09m 54.2s) | C | 180 | 19.9 | Coadd
111193 | 2026-05-13 23:49:26 | MASTER-OAFA | (10h 11m 01.87s , -82d 10m 51.8s) | C | 60 | 19.5 |
111266 | 2026-05-13 23:50:39 | MASTER-OAFA | (10h 10m 56.31s , -82d 11m 49.2s) | C | 60 | 19.5 |
111342 | 2026-05-13 23:51:55 | MASTER-OAFA | (10h 11m 03.48s , -82d 11m 44.4s) | C | 60 | 19.6 |
111416 | 2026-05-13 23:53:10 | MASTER-OAFA | (10h 11m 03.76s , -82d 09m 59.6s) | C | 60 | 19.6 |
111493 | 2026-05-13 23:54:26 | MASTER-OAFA | (10h 11m 03.44s , -82d 11m 36.7s) | C | 60 | 19.6 |
111569 | 2026-05-13 23:55:42 | MASTER-OAFA | (10h 11m 08.67s , -82d 10m 08.0s) | C | 60 | 19.3 |
111642 | 2026-05-13 23:56:55 | MASTER-OAFA | (10h 11m 04.41s , -82d 10m 48.5s) | C | 60 | 18.6 |
111721 | 2026-05-13 23:58:14 | MASTER-OAFA | (10h 11m 06.38s , -82d 09m 49.6s) | C | 60 | 18.2 |
111805 | 2026-05-13 23:59:38 | MASTER-OAFA | (10h 08m 14.34s , -84d 04m 05.1s) | C | 60 | 17.5 |
111880 | 2026-05-14 00:00:53 | MASTER-OAFA | (10h 08m 08.20s , -84d 05m 00.1s) | C | 60 | 17.9 |
111956 | 2026-05-14 00:02:09 | MASTER-OAFA | (10h 08m 17.81s , -84d 04m 38.0s) | C | 60 | 18.2 |
112035 | 2026-05-14 00:03:28 | MASTER-OAFA | (10h 12m 11.06s , -80d 13m 12.6s) | C | 60 | 18.4 |
112111 | 2026-05-14 00:04:44 | MASTER-OAFA | (10h 12m 11.82s , -80d 14m 41.3s) | C | 60 | 18.3 |
112186 | 2026-05-14 00:05:59 | MASTER-OAFA | (10h 12m 17.07s , -80d 13m 35.4s) | C | 60 | 18.6 |
112262 | 2026-05-14 00:07:15 | MASTER-OAFA | (09h 58m 34.51s , -80d 14m 16.2s) | C | 60 | 19.3 |
112341 | 2026-05-14 00:08:34 | MASTER-OAFA | (09h 58m 35.92s , -80d 13m 16.8s) | C | 60 | 19.3 |
112416 | 2026-05-14 00:09:49 | MASTER-OAFA | (09h 58m 42.73s , -80d 14m 14.8s) | C | 60 | 19.3 |
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 44591
Subject
GRB 260512A: NuSTAR detection of prompt emission
Date
2026-05-12T23:53:06Z (15 days ago)
Edited On
2026-05-13T14:52:27Z (14 days ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:
The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260512A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm, triggered at 2026-05-12T16:56:43.530 UTC, shows a detection of GRB 260512A, also detected by Fermi/GBM (Fermi GBM Team, GCN 44587).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a 10-s long burst consistent with the Fermi/GBM lightcurve. The peak count rate is ~2500-cps with a baseline rate of ~1000-cps during this time period. We do not see evidence in the signal above 100 keV in the CZT detectors.
The Fermi/GBM localization (GCN 44587) at RA = 153.56, Dec = -82.64 implies an offset from the NuSTAR boresight of 15-deg (i.e. near the boresight) and an offset from the geocenter of 96-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260512A
Information on NuSTAR SINGS can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/
NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.
GCN Circular 44587
Subject
GRB 260512A: Fermi GBM Final Real-time Localization
Date
2026-05-12T17:07:17Z (15 days 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 LONG GRB
At 16:56:43 UT on 12 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260512A (trigger 800297808.529848 / 260512706).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 153.6, Dec = -82.6 (J2000 degrees, equivalent to J2000 10h 14m, -82d 35'), with a statistical uncertainty of 2.0 degrees.
The angle from the Fermi LAT boresight is 136.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260512706/quicklook/glg_skymap_all_bn260512706.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/bn260512706/quicklook/glg_healpix_all_bn260512706.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260512706/quicklook/glg_lc_medres34_bn260512706.gif