GRB 260510B
GCN Circular 44566
Subject
GRB 260510B: EP-FXT follow-up observation
Date
2026-05-12T02:31:52Z (9 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
A. Li (BNU), S.-Y. Fu (HUST), 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 260510B (SVOM/sb26051001, Saccardi et al., GCN 44515). The follow-up obervation started at 2026-05-10T13:15:11 UTC, approximately 55 minutes after the SVOM trigger, with a total exposure time of 6.1 ks.
On-ground analysis of the FXT data found an uncatalogued fading source at R.A., Dec. = 173.2323, -34.5399 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic) within the ECLAIRs error circle. 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 2.24 (-0.56/+0.60). The derived average unabsorbed flux in the 0.5-10 keV band is 1.17 (-0.3/+1.7)×10^-12 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 44550
Subject
GRB 260510B: SVOM/ECLAIRs refined analysis
Date
2026-05-11T14:12:00Z (9 days ago)
Edited On
2026-05-12T13:42:16Z (8 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
N. Dagoneau (CEA), A. Saccardi (CEA), B. Cordier (CEA), 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 ECLAIRs observations of GRB 260510B (SVOM burst-id sb26051001).
The burst that triggered ECLAIRs onboard (GCN 44515) consists of a multiple peaks lightcurve with a duration of T90 = 12.05 -3.49 / +2.22 s in the 4-120 keV energy band.
The time-averaged spectrum (from T0-4.87 to T0+7.16s) in the energy range 5-120 keV is best fitted by a simple power-law model with a photon index -1.43 +/- 0.12. With this model,the 4-120 keV fluence is (4.604 ± 0.481)E-7 erg/cm² and the 4-120 keV photon flux is 0.93 ± 0.09 ph/cm²/s.
All the quoted errors are at the 68% confidence level.
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.
The SVOM/ECLAIRs point of contact for this burst is: Nicolas Dagoneau (CEA) (nicolas.dagoneau at cea.fr)
GCN Circular 44528
Subject
GRB 260510B: SVOM/VT optical upper limits
Date
2026-05-11T03:48:57Z (9 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 GRB260510B triggered by SVOM/ECLAIRs (sb26051001, Saccardi et al., GCN 44515). The burst was also detected at sub-threshold level by Fermi-GBM (Palafox et al., GCN 44524). VT observations started at 2026-05-10T12:23:54 UTC, 274 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/ECLAIRs (Saccardi et al., GCN 44515), 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
23.3 min VT_B 45*50 sec > 23.0 mag
23.3 min VT_R 45*50 sec > 23.0 mag
Our non-detection is consistent with the non-detections reported by LCO (Saccardi et al., GCN 44518) and GOTO (Ramsay et al., GCN 44522).
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 44524
Subject
Fermi GBM Sub-Threshold Detection of GRB 260510B
Date
2026-05-10T21:21:21Z (10 days ago)
From
Eva MP at INAOE <eva.palafox@gmail.com>
Via
Web form
E. Palafox (INAOE) reports on behalf of the Fermi-GBM Team:
SVOM/ECLAIRs detected GRB 260510B on 2026-05-10 at 12:19:20 UTC (A. Saccardi et al. 2026, GCN 44515). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no candidates.
The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient approximately 3 s after the ECLAIRs best image SNR time of 2026-05-10T12:19:15. The Targeted Search candidate was found most significantly on the 8 s timescale using the "normal" spectral template (i.e., Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) and has a false alarm rate of 1.1e-04 Hz. The Fermi-MET of the start time of this transient is 800108363.27 s. The Targeted Search localization is found to be spatially consistent with the ECLAIRs one, with a spatial association probability of 98.6%.
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular 44522
Subject
GRB 260510B: GOTO early upper limit
Date
2026-05-10T17:44:24Z (10 days ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
G. Ramsay, D. O'Neill, S. Belkin, K. Ulaczyk, A. Kumar, K. Ackley, M. Dyer, J. Lyman, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, B. Gompertz, B. Godson, T. Killestein, M. Pursiainen, 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 SVOM/ECLAIRS alert GRB 260510B (sb26051001, Saccardi et al. GCN 44515). Observations covering the full extent of the localisation area were started at 2026-05-10 12:23:17 UT, (t0 +4 min) in the L band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations (Lyman et al. 2026). 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.
Observations at 2026-05-10 12:23:17 UT (t0 +4 min) and 2026-05-10 13:30:27 UT (t0 +1.19h) did not reveal any new counterpart down to a localised 5-sigma limit of 20.3 and 20.5 AB mag respectively. The GOTO non-detection is consistent with that reported by Saccardi et al (GCN 44518).
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 44518
Subject
GRB 260510B: LCO optical upper limits
Date
2026-05-10T15:18:38Z (10 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi (CEA/Irfu), C. Wu (NAOC), L. Zhang (IHEP), Y. H. Cheng (YNU), report on behalf of the SVOM mission team:
We observed the field of GRB 260510B detected by SVOM (Saccardi et al., GCN 44515) with the LCO 1m telescope at Siding Spring Observatory equipped with the Sinistro instrument.
Our observation started on 2026-05-10 at 12:33:06 UT (about 14 min after the trigger) and we obtained 2x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters.
In the stacked images, we do not detect any new source within the SVOM/ECLAIRs error box. We measure the following upper limits calibrated against the DESI DR10 catalog, and not corrected for Galactic extinction:
r > 20.7 AB (5-sigma, mid-time 1.9 hr after the trigger);
z > 20.0 AB (5-sigma, mid-time 19 min after the trigger).
This project is funded by the SVOM collaboration.
GCN Circular 44515
Subject
GRB 260510B: SVOM detection of a burst
Date
2026-05-10T12:49:03Z (10 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi (CEA/Irfu), B. Cordier (CEA/Irfu), N. Dagoneau (CEA/Irfu), Li. Zhang(IHEP), Y. H. Cheng (SWIFAR, YNU), report on behalf of the SVOM mission team:
At 2026-05-10T12:19:20 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260510B (SVOM burst-id sb26051001).
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 9.71 in the [8-50] keV energy band over a time window of 10.20 seconds starting at 2026-05-10T12:19:15.
The localization of the best alert is R.A., Dec. 173.2168, -34.5756 degrees:
R.A. (J2000) = 11h32m52.04s
Dec. (J2000) = -34d34m32.07s
with a 90% confidence level (C.L.) radius of 8.18 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst was also detected by SVOM/GRM with a significance of 7.40.
SVOM slewed to the burst.
MXT and VT began observing the field after the slew. The analysis of the data will be published in future circulars.
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 zhangli: zhangli@ihep.ac.cn
Please contact the BA by email if you require additional information.