GRB 260510C
GCN Circular 44621
Subject
GRB 260510C: Glowbug gamma-ray detection
Date
2026-05-15T18:39:46Z (7 days ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
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 260510C, which was detected by Fermi/GBM (GCN 44520, 44564), SVOM (GCN 44521), MAXI/GSC (GCN 44526), AstroSat/CZTI (GCN 44544), and CALET (GCN 44616).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-10 17:15:37.096 with a duration of 4.1 s and a total significance of about 5.2 sigma. The lightcurve comprises a single peak corresponding to the portion of the burst observed by CALET/CGBM (GCN 44616).
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 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 44616
Subject
GRB 260510C: CALET Gamma-Ray Burst Monitor detection
Date
2026-05-15T07:23:20Z (7 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
T. Sakamoto, A. Yoshida, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260510C
(Fermi GBM Final Real-time Localization: Fermi GBM team, GCN #44520;
SVOM detection of a burst: Gotz et al., GCN #44521; MAXI/GSC detection:
Iwakiri et al., GCN #44526; AstroSat CZTI detection: Arya et al., GCN #44544;
Fermi GBM Observation: Palafox et al., GCN #44564) at 17:15:37.60 UTC on 10 May 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1462468483/index.html).
The burst signal was seen by all CGBM detectors. The onboard CGBM trigger
corresponds to the second peak of the double-peaked structure reported by
Fermi/GBM and SVOM/ECLAIRs. In the CGBM ground analysis, the first peak was also
marginally visible in the SGM data. The second peak started at T+0.3 s,
peaked at T+2.9 s, and ended at T+8.9 s. The T90 and T50 durations of the
second peak, measured with the SGM data, are 7.4 +/- 0.8 s and 3.2 +/- 0.8 s
in the 40-1000 keV band, respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1462468483/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 44589
Subject
GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
Date
2026-05-12T20:44:36Z (10 days ago)
From
Geoffrey Mo at Caltech / Carnegie Observatories <gmo@mit.edu>
Via
Web form
Geoffrey Mo (Carnegie/Caltech), K. De, V. Karambelkar, S. Ibrahim, D. Schiminovich (Columbia University) report:
We observed the field of GRB 260510C (Fermi GBM Team, GCN 44520; Gotz et al., GCN 44521; Iwakiri et al., GCN 44526; Fu et al., GCN 44541; Arya et al., GCN 44544; Palafox et al., GCN 44564) in the near-infrared J and Hs bands with the MDM InfraRed Astronomy inGaas Explorer (MIRAGE) instrument on the MDM 1.3 m telescope.
Observations began at 2026-05-11T03:31:14 (+10.3 hours after the GRB trigger) in the J band and 2026-05-11T04:04:31 (+10.8 hours) in the Hs band, lasting 1620 s in each filter.
The optical counterpart (Li et al, GCN 44527; Angulo et al., GCN 44530; Li et al., GCN 44540; Lee et al., GCN 44570) is detected in both filters, with the following AB magnitudes: J = 19.64 ± 0.16, Hs = 19.42 ± 0.24.
MIRAGE is a new YJHs-band near-infrared imager for the MDM 1.3m telescope. We thank the MDM Observatory staff for supporting the observations.
GCN Circular 44570
Subject
GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
Date
2026-05-12T05:34:29Z (10 days ago)
Edited On
2026-05-13T12:50:22Z (9 days ago)
From
William H. Lee at UNAM <wlee@astro.unam.mx>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of William H. Lee at UNAM <wlee@astro.unam.mx>
Via
Web form
William H. Lee (UNAM), Dalya Akl (NYUAD), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), and Andrea Saccardi (CEA/Irfu) report:
We reimaged the field of the SVOM/ECLAIRs and Fermi/GBM GRB 260510C (Fermi GBM Team, GCN Circ. 44520; Gotz et al., GCN Circ. 44521) and also detected by AstroSat (Arya et al. GCN Circ. 44544) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-12 03:45 to 04:44 UTC (from 34.52 to 35.53 hours after the trigger) and obtained 47 minutes of simultaneous exposure in r and z filters.
The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline.
The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detect the source reported by Angulo et al. (GCN Circ. 44530) with preliminary unsubtracted magnitudes of:
r = 22.36 + /- 0.07,
z = 21.33 + /- 0.08.
Compared with our first epoch (Angulo et al. GCN Circ. 44530), we estimate an optical decay temporal index of alpha ≈ -0.9 for the source.
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular 44564
Subject
GRB 260510C: Fermi GBM Observation
Date
2026-05-11T20:51:58Z (11 days ago)
From
Eva MP at INAOE <eva.palafox@gmail.com>
Via
Web form
E. Palafox (INAOE, Mexico) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 17:13:43.99 UT on 10 May 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260510C (trigger 800126028/260510718),
which was also detected by SVOM/ECLAIRs (Gotz et al. 2026, GCN 44521),
MAXI (Iwakiri et al. 2026, GCN 44526), COLIBRI (Angulo et al. 2026, GCN 44530),
SVOM/VT (Li et al. 2026, GCN 44527 and GCN 44540), EP-FXT (Fu et al. 2026, GCN 44541)
and AstroSat CZTI (Arya et al. 2026,GCN 44544).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.
The angle from the Fermi LAT boresight is 68 degrees.
The GBM light curve consists of two bright emission episodes with a duration (T90)
of about 162 s (50-300 keV). The time-averaged spectrum
from T0-8.2 to T0+143.4 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.3 +/- 0.2 and the cutoff energy,
parameterized as Epeak, is 176 +/- 55 keV.
The event fluence (10-1000 keV) in this time interval is
(4.9 +/- 0.7)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+120 s in the 10-1000 keV band is 2.6 +/- 0.3 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 44544
Subject
GRB 260510C: AstroSat CZTI detection
Date
2026-05-11T11:30:38Z (11 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (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 long GRB 260510C which is also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44520), SVOM/GRM (Gotz et al., GCN Circ. 44521), and MAXI/GSC (Iwari et al., GCN Circ. 44526).
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-05-10 17:15:41.94 UTC. The measured peak count rate associated with the burst is 168 (+65, -24) counts/s above the background in the combined data of all quadrants, with a total of 1298 (+346, -375) counts. The local mean background count rate was 1125 (5, -6) counts/s. We measure a T90 of 14 (+3, -3) s from the cumulative Veto light curve.
The source was also faintly detected in the CZT detectors in the 20-200 keV energy range.
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 44541
Subject
GRB 260510C: EP-FXT follow-up observation
Date
2026-05-11T10:10:16Z (11 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
S.-Y. Fu (HUST), A. Li (BNU), C.-Y. Wang (THU), R. Shi (PMO), Y. Liu (NAOC, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260510C (SVOM/sb26051004, Gotz et al., GCN 44521), which also triggered Fermi-GBM (Fermi GBM team, GCN 44520) and MAXI/GSC (Iwakiri et al., GCN 44526). The follow-up obervation started at 2026-05-10T18:03:40 UTC, approximately 50 minutes after the SVOM trigger, with a total exposure time of 5370 s.
On-ground analysis of the FXT data found an uncatalogued fading source at R.A., Dec. = 157.9391, 2.837 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic) within the ECLAIRs error circle, which is spatially consistent with the optical counterpart (Angulo et al., GCN 44530; Li et al., GCN 44540). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power-law model, with the hydrogen column density fixed at the Galactic value and a photon index of 2.15 (-0.07/+0.07). The derived average unabsorbed flux in the 0.5-10 keV band is 4.1 (-0.1/+0.1)×10^-11 erg s^-1 cm^-2.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular 44540
Subject
GRB 260510C: SVOM/VT optical counterpart confirmation
Date
2026-05-11T09:42:07Z (11 days ago)
Edited On
2026-05-11T13:40:03Z (11 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
We refined the analysis of SVOM/VT images (Li et al., GCN 44527) on GRB 260510C (Gotz et al., GCN 44521; Fermi GBM team, GCN 44520; Iwakiri et al., GCN 44526) with more data available. The optical counterpart found by SVOM/COLIBRÍ (Angulo et al., GCN 44530) was clearly detected in both channels of SVOM/VT. The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | Brightness
1.79 h VT_B 40*50 sec 21.13 +/- 0.09 mag
1.18 h VT_R 41*50 sec 19.94 +/- 0.06 mag
8.06 h VT_B 9*100 sec 22.13 +/- 0.14 mag
8.14 h VT_R 3*100 sec 20.61 +/- 0.08 mag
The source showed a fading slope of about -0.45 during the observations above.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 44530
Subject
GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
Date
2026-05-11T06:35:13Z (11 days ago)
From
Camila Angulo Valdez at UNAM <camiangulo@astro.unam.mx>
Via
Web form
Camila Angulo (UNAM), Dalya Akl (NYUAD), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) and Andrea Saccardi (CEA/Irfu
) report:
We imaged the field of the SVOM/ECLAIRs and Fermi/GBM GRB 260510C (Fermi GBM Team, GCN Circ. 44520; Gotz et al., GCN Circ. 44521) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-11 04:46 to 05:39 UTC (from 11.54 to 12.44 hours after the trigger) and obtained 24 minutes of simultaneous exposure in r and z filters.
The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline.
The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detect an uncatalogued source 1.06 arcmin away from the MXT position and slightly outside the 90% uncertainty region reported by SVOM, but still inside the ECLAIRs region (Gotz et al., GCN Circ. 44521), at:
RA(J2000) = 10:31:45:49 = 157.9394 degrees
Dec(J2000) = +02:50:15.5 = 2.83763 degrees
with an uncertainty of 0.5 arcsec. The preliminary unsubtracted magnitudes derived for that source are:
r = 21.32 + /- 0.03,
z = 20.23 + /- 0.03.
We suggest this is the optical counterpart of the GRB. The position of the candidate is consistent with a faint galaxy with reported magnitudes of g = 23.61 +/- 0.10, r = 23.49 +/- 0.14, i = 23.02 +/- 0.12 and z = 23.03 +/- 0.21 and a photo-z of =0.89 +/- 0.63 in the DESI Legacy Survey catalog (Dey et al. 2019), so our candidate is two magnitudes brighter than the galaxy. We suggest this galaxy may be the host.
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular 44527
Subject
GRB 260510C: SVOM/VT optical upper limits
Date
2026-05-11T01:03:32Z (11 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
SVOM/VT performed automatic observations of GRB260510C triggered by SVOM/ECLAIRs (sb26051004, Gotz et al., GCN 44521). The burst was also detected by Fermi GBM (Fermi GBM team, GCN 44520) and MAXI/GSC (Iwakiri et al., GCN 44526). The VT observations started at 2026-05-10T17:18:48 UTC, i.e., 304 seconds post trigger, in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
No uncatalogued sources were detected within the error box of SVOM/MXT (Gotz et al., GCN 44521) and SVOM/ECLAIRs (Gotz et al., GCN 44521), compared to the Legacy Survey. The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | 3 sigma upper limit
1.10 h VT_B 47*50 sec > 23.2 mag
1.18 h VT_R 41*50 sec > 23.1 mag
Further analyses are ongoing.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 44526
Subject
GRB 260510C: MAXI/GSC detection
Date
2026-05-10T21:42:33Z (12 days ago)
From
Wataru Iwakiri at Chiba University <iwakiri.wataru.buz@gmail.com>
Via
Web form
W. Iwakiri (Chiba U.), M. Serino(AGU),
H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.),
T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU),
Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.),
M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.),
I. Takahashi, Y. Yatsu (Science Tokyo),
S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA),
Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.),
M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (Kanazawa U.),
T. Kawamuro (Osaka U.),
S. Yamada (Tohoku U),
S. Ogawa (TUS)
report on behalf of the MAXI team:
At 17:13:42 UT on 2026 May 10, the MAXI/GSC nova alert system triggered
a bright uncatalogued X-ray transient source. The trigger time and
position are consistent with GRB 260510C reported by the Fermi team
(GCN #44520) and the SVOM team (GCN #44521).
The X-ray flux averaged over the scan was 338 +/- 36 mCrab (4.0-10.0 keV,
1-sigma error).
Assuming that the source flux was constant over the transit, we obtain
the source position at:
(R.A., Dec) = (157.881 deg, 2.824 deg) = (10 31 31, +02 49 26) (J2000)
with a statistical 90% C.L. elliptical error region with long and short
radii of 0.17 deg and 0.14 deg, respectively. The roll angle of the long
axis is 73.0 deg counterclockwise from the north. There is an additional
systematic uncertainty of 0.1 deg (90% containment radius).
Without assumptions on the source constancy, we obtain a rectangular
error box for the transient source with the following corners:
(157.267, 2.290) deg = (10 29 04, +02 17 24) (J2000)
(157.477, 2.117) deg = (10 29 54, +02 07 01) (J2000)
(158.505, 3.360) deg = (10 34 01, +03 21 35) (J2000)
(158.295, 3.533) deg = (10 33 10, +03 31 58) (J2000)
There was no significant excess flux in the previous transit at 15:40 UT
with an upper limit of 20 mCrab.
GCN Circular 44521
Subject
GRB 260510C: SVOM detection of a burst
Date
2026-05-10T17:42:51Z (12 days ago)
From
Diego Gotz at CEA <diego.gotz@cea.fr>
Via
Web form
D. Gotz (CEA/Irfu), A. Saccardi (CEA/Irfu), S. Schanne (CEA/Irfu), N. Dagoneau (CEA/Irfu) report on behalf of the SVOM mission team:
At 2026-05-10T17:13:44 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260510C (SVOM burst-id sb26051004), also detected by Fermi/GBM (Fermi GRB Team, GCN #44520).
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 11 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 12.18 in the [8-120] keV energy band over a time window of 10.20 seconds starting at 2026-05-10T17:13:38.
The localization of the best alert is R.A., Dec. 157.9595, 2.8711 degrees (J2000) with a 90% confidence level (C.L.) radius of 6.63 arcmin (including systematic error of 2 arcmin added in quadrature).
The SVOM/ECLAIRs light curve showed a double peaked structure with a total duration of about 150 s.
This burst was also detected by SVOM/GRM with a significance of 7.50.
The SVOM/GRM light curve showed two separated peaks with a total duration of about 150 s.
SVOM slewed to the burst.
SVOM/MXT began observing the field at 2026-05-10T17:16:44 UTC, 179 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 157.941, +2.820 degrees:
R.A. (J2000) = 10h31m45.8s
Dec. (J2000) = 02d49m12.0s
with a 90% C.L. radius of 45 arcseconds.
This location is 3.26 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.
VT began observing the field after the slew. The analysis of the data will be published in a future circular.
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 Andrea Saccardi: andrea.saccardi@cea.fr.
Please contact the BA by email if you require additional information.
GCN Circular 44520
Subject
GRB 260510C: Fermi GBM Final Real-time Localization
Date
2026-05-10T17:24:27Z (12 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 17:13:43 UT on 10 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260510C (trigger 800126028.99095 / 260510718).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 174.6, Dec = 8.6 (J2000 degrees, equivalent to J2000 11h 38m, 8d 35'), with a statistical uncertainty of 10.4 degrees.
The angle from the Fermi LAT boresight is 66.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260510718/quicklook/glg_skymap_all_bn260510718.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/bn260510718/quicklook/glg_healpix_all_bn260510718.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260510718/quicklook/glg_lc_medres34_bn260510718.gif