GRB 260412A
GCN Circular 44378
Subject
GRB 260412A: SVOM/ECLAIRs refined analysis
Date
2026-04-21T13:31:47Z (4 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Marius Brunet (IRAP), Wenjin XIE (NAOC), Olivier Godet (IRAP), Ziqi Wang (GXU), Zhiyong Liu(GZNU) report on behalf of the SVOM/ECLAIRs team
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260412A (SVOM burst-id sb26041206 – GCN 44276, trigger time T0 = 2026-04-12T06:13:35 UTC), which was also detected by Fermi (GCN 44275, 44279), GECAM (GCN 44281) and HXMT (GCN 44294).
The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve with late peaks at around T0+80s and T0+160s. The burst duration is T90 = 165.0 +2.6/-1.6 s in the 4-120 keV energy band.
The time-averaged spectrum from T0-3.5 s to T0+200.5 s in the energy range 4-120 keV is best fitted by a powerlaw model with best-fit parameters – alpha = -1.5 +/-0.3. With this model, the 4-120 keV fluence is 7.4 +/- 0.3 e-6 erg/cm^2.
Using the same Fermi/GBM time window as in Palafox et al. (GCN 44279), we retrieve a consistent photon index value when using a cutoff model and fixing Epeak at 210 keV.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.
The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr)
GCN Circular 44356
Subject
GRB 260412A: LCOGT Optical Upper Limits
Date
2026-04-20T17:36:58Z (5 days ago)
From
Robert Strausbaugh at Eastern Illinois University <rstrausbaugh@eiu.edu>
Via
email
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the GRB260412A field (Fermi GBM Team, GCN 44275; Wang et al., GCN 44276) with the LCOGT 1-meter Sinistro instrument at the South African Astronomical Observatory, South Africa site, on April 12, from 17:13 to 17:26 UT (corresponding to 11.0 to 11.2 hours after the trigger time) and with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, from 23:20 to 23:52 (17.1 to 17.7 hours after the trigger time) with the Bessel I and R filters.
We performed a series of 3x300s exposures in I-band and 1x100s exposure in R-band due to a scheduling interruption, and then 3x300s in I-band and R-band for the second epoch. We do not detect an uncatalogued source within the SVOM error region (Wang et al., GCN 44276), consistent with other optical upper limits (Lipunov et al., 44280).
The following 5-sigma upper limits are calculated using the USNO-B1.0 catalog as reference:
Epoch 1:
I>20.7
R>17.3
Epoch 2:
I>21.0
R>22.6
These magnitudes are not corrected for galactic extinction.
GCN Circular 44294
Subject
GRB 260412A: Insight-HXMT/HE detection
Date
2026-04-14T07:29:11Z (11 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, Cheng-Kui Li and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
At 2026-04-12T06:13:46.169 (T0), Insight-HXMT/HE detected the burst GRB 260412A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #44275), SVOM/ECLAIRs(Ziqi Wang et.al., GCN#44276) and GECAM-B(Xing-Hao Luo.et.al., GCN#44281).
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 40 +4/-6 s. The 1s peak rate, measured from T0+23 s, is 1028 cnts/sec. Insight-HXMT/HE detected a total of 9203 counts from this burst.
The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260412A.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 44281
Subject
GRB 260412A: GECAM-B observation of a long burst
Date
2026-04-13T06:10:54Z (12 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Chao Zheng, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered on-ground by GRB 260412A, at 2026-04-12T06:13:49.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44275) and SVOM/ECLAIRs (Ziqi Wang et.al., GCN#44276).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 32 +6/-4 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260412A.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 44280
Subject
Fermi GRB 260412A: Global MASTER-Net observations report
Date
2026-04-13T00:02:11Z (12 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 260412A ( Fermi GBM team, GCN 44275) errorbox 62093 sec after notice time and 62124 sec after trigger time at 2026-04-12 23:29:10 UT, with upper limit up to 20.6 mag. Observations started at twilight. The observations began at zenith distance = 47 deg. The sun altitude is -16.0 deg.
The galactic latitude b = -41 deg., longitude l = 253 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3247887
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
62184 | 2026-04-12 23:29:10 | MASTER-OAFA | (04h 21m 09.48s , -47d 04m 33.5s) | C | 120 | 20.6 |
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 44279
Subject
GRB 260412A: Fermi GBM Observation
Date
2026-04-12T21:58:16Z (12 days ago)
From
Eva MP at INAOE <eva.palafox@gmail.com>
Via
Web form
E. Palafox (INAOE) and U. Pathak (IIT Bombay) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 06:13:46.17 UT on 12 April 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260412A (trigger 797667231/260412260).
which was also detected by SVOM/ECLAIRs (Wang et al. 2026, GCN 44276).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.
The angle from the Fermi LAT boresight is 35 degrees.
The GBM light curve consists of a bright emission episode with multiple peaks with a duration (T90)
of about 80 s (50-300 keV). The time-averaged spectrum
from T0-19 to T0+60 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.28 +/- 0.07 and the cutoff energy,
parameterized as Epeak, is 210 +/- 30 keV.
The event fluence (10-1000 keV) in this time interval is
(7.9 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+22 s in the 10-1000 keV band is 3 +/- 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 44276
Subject
GRB 260412A: SVOM detection of a long burst
Date
2026-04-12T06:57:17Z (13 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Ziqi Wang (GXU), Zhiyong Liu(GZNU), Hatsune GOTO(RIKEN), Wenjin XIE(NAOC), Ulysse Jacob (LUPM)
report on behalf of the SVOM mission team:
At 2026-04-12T06:13:46 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260412A (SVOM burst-id sb26041206), which is also detected by Fermi/GBM (Fermi GBM Team, GCN 44275).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 67 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 42.64 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2026-04-12T06:13:35.
The localization of the best alert is R.A., Dec. 79.9074, -44.5851 degrees:
R.A. (J2000) = 5h19m37.78s
Dec. (J2000) = -44d35m06.31s
with a 90% confidence level (C.L.) radius of 2.69 arcmin (including systematic error of 2 arcmin added in quadrature).
The SVOM/ECLAIRs preview VHF light curve showed multiple broad peak structures with a T90 duration of about 321.20 (-2.00 +1.89) s in the 5-120 keV energy band.
Due to SVOM performing another ToO-EX during the trigger, no immediate slew was performed on this burst.
No X-ray observation could be performed by SVOM/MXT for the time being.No optical observation could be performed by SVOM/VT for the time being.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.
The Burst Advocate (BA) on shift for this alert is Ziqi Wang: ziqi.wang@st.gxu.edu.cn.
Please contact the BA by email if you require additional information.
GCN Circular 44275
Subject
GRB 260412A: Fermi GBM Final Real-time Localization
Date
2026-04-12T06:24:26Z (13 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 06:13:46 UT on 12 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260412A (trigger 797667231.169604 / 260412260).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 70.0, Dec = -47.3 (J2000 degrees, equivalent to J2000 04h 40m, -47d 17'), with a statistical uncertainty of 5.7 degrees.
The angle from the Fermi LAT boresight is 31.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260412260/quicklook/glg_skymap_all_bn260412260.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/bn260412260/quicklook/glg_healpix_all_bn260412260.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260412260/quicklook/glg_lc_medres34_bn260412260.gif