GRB 260225A
GCN Circular 43909
Subject
GRB 260225A: SVOM/ECLAIRs refined analysis
Date
2026-03-03T14:56:16Z (7 days ago)
Edited On
2026-03-03T15:09:47Z (7 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
M. Brunet, O. Godet (IRAP), W.J. Xie (NAOC), F. Daigne (IAP),Yinuo Ma (NAOC), Li Zhang (IHEP) 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 260225A (SVOM burst-id sb26022501 – GCN 43829, trigger time T0 = 2026-02-25T08:51:15 UTC).
The burst that triggered ECLAIRs shows a single peak lightcurve. The burst duration before the satellite slew is estimated through imaging to be around 59 s (from T0-21 s up to T0+38 s) in the 4-120 keV energy band. Some emission below 20 keV is still seen after the slew up to T0+209 s.
The time-averaged spectrum before the satellite slew, i.e. from T0-21 s to T0+38 s in the 5-120 keV energy band is best fitted by a broken power-law model with a first photon index of -1.00 +0.20/-0.16, a break energy of 21.7 +4.4/-3.9 keV and a second photon index of -2.06 +0.22/-0.28. With this model, the 4-120 keV fluence is (1.00 +0.04/-0.26)e-6 erg/cm^2.
The spectral parameters indicate that this burst is likely to be an X-ray flash.
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. 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 43872
Subject
GRB 260225A: SVOM/VT optical continued observations and upper limit
Date
2026-02-28T05:02:37Z (11 days ago)
From
Yinuo Ma <mayn@bao.ac.cn>
Via
Web form
Y. N. Ma, Z. H. Yao, H. L. Li, Y. L. Qiu, C. Wu, L. P. Xin, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), L. Zhang (IHEP) report on behalf of the SVOM/VT team.
SVOM/VT continued observations of GRB 260225A (sb26022501) triggered by SVOM/ECLAIRs (Ma et al., GCN 43829). With X-band data available, the optical counterpart (Ducoin et al., GCN 43837; Li et al., GCN 43838; Schneider et al., GCN 43861) within EP/FXT error box (Yang et al., GCN 43839) was detected in VT_B band. The magnitudes are:
mid time (h) | exposure time (s) | band | mag (AB)
-------------|-------------------|------|------------
35.08 | 37*70 | VT_B | 23.6+/-0.3
35.04 | 27*70 | VT_R | >23.3
Our photometry was not corrected for Galactic extinction.
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 43861
Subject
GRB 260225A: WINTER J-band upper limit
Date
2026-02-27T09:35:03Z (11 days ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of the SVOM GRB 260225A (Ma et al., GCN Circ. 43829) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2026-02-25 at 09:09:10 UT (17.92 min after the trigger) and consisted of 15 exposures of 120 s in the J-band.
The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) and analysed with STDWeb/STDPipe (Karpov 2025). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction.
In the stacked image, the optical counterpart reported by Ducoin et al., GCN Circ. 43839 and Li et al., GCN Circ. 43838, consistent with the uncatalogued X-ray source detected by EP/FXT position (Yang et al., GCN 43839), is not detected down to the following 3-sigma AB magnitude:
J > 19.5
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 43841
Subject
GRB260225A: SVOM/ECLAIRs refined position
Date
2026-02-26T11:19:51Z (12 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, O. Godet (IRAP), on behalf of the ECLAIRs team report:
Using the event-by-event data downloaded through the X-band ground station, we were able to improve the ECLAIRs position of GRB 260204A (SVOM burst-id sb26022501, Ma et al., GCN 43829) as: R.A., Dec.: 204.7191, 44.6194 degrees:
R.A. (J2000) = 13h38m52.58s
Dec. (J2000) = 44d37m09.84s
with a 90% confidence level (C.L.) radius of 7.1 arcmin.
Within this refined position, a counterpart has been detected in optical by SVOM/COLIBRÍ (Ducoin et al., GCN 43837) and SVOM/VT (Li et al., GCN 43838) as well as in X-rays by EP/FXT (Yang et al., GCN 43839).
The Space 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. ECLAIRs was developed jointly by CNES, IRAP, APC and CEA.
The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr)
GCN Circular 43839
Subject
GRB 260225A: EP-FXT follow-up observation
Date
2026-02-26T04:07:27Z (13 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Guojiong Yang(NAO, CAS), Jiaying Cao(IHEP), Wenfeng Wen(SZTU) and Haiwu Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260225A (SVOM/sb26022501; Ma et al., GCN 43829) starting at 2026-02-25T09:26:28 UTC, approximately 35 minutes after the SVOM trigger, with a total exposure time of 6090 s.
At the optical position reported by Basa et al. (GCN Circ. 43837), an uncatalogued X-ray source (EPF_J133924.5+443450; RA, Dec = 204.852, 44.5806, J2000) is detected, with a 90% confidence positional uncertainty of 2.1 arcsec (statistical only).
The spectrum can be well fitted with an absorbed power-law model, with the Galactic hydrogen column density. The best-fit photon index is about 1.56.
The corresponding unabsorbed flux in the 0.5–10 keV band is 1.89×10^-12 erg cm^-2 s^-1
Flux_err: 2.3 × 10^-13 erg cm^-2 s^-1 (1σ)
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 43838
Subject
GRB 260225A: SVOM/VT optical observation
Date
2026-02-26T03:29:53Z (13 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), D. Turpin (CEA) and L. Zhang (IHEP) report on behalf of the SVOM/VT team.
Following the report of the optical counterpart (Ducoin et al., GCN 43837) by SVOM/COLIBRÍ (Basa et al., GCN 43830), we reanalyzed SVOM/VT Xband data (Li et al., GCN 43834) for GRB 260225A (Ma et al., GCN 43829). The source was detected by SVOM/VT in both channels. The measurements in AB magnitude are derived as follows:
Mid time | Band | Exposure Time | Magnitude
1.13 hours VT_B 52*50 sec 22.09 +/- 0.16 mag
1.07 hours VT_R 41*50 sec 22.00 +/- 0.20 mag
Our photometry was not corrected for Galactic extinction.
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 43837
Subject
GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
Date
2026-02-26T00:08:25Z (13 days ago)
From
Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr>
Via
Web form
Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), Diego López-Cámara (UNAM), Benjamin Schneider (LAM), Damien Dornic (CPPM), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), and L. Zhang (IHEP) report:
The data reported in the GCN by Basa et al. (GCN Circ. 43830) have been reanalyzed following an improved localization provided by ECLAIRs (private communication).
The images have been acquired by the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-02-25 09:02 UTC to 10:24 UTC (from 0.18 to 1.57 hours after the trigger) and obtained 64 minutes of exposure.
The data were reduced and analyzed with the COLIBRÍ pipeline, and also analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the Pan-STARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detect an uncatalogued source revealed by image subtraction using Legacy Survey as template and consistent with the new ECLAIRs localization at:
RA(J2000) = 13:39:24.56 = 204.852333 degrees
Dec(J2000) = 44:34:51.0 = 44.580833 degrees
with an uncertainty of 0.5 arcsec.
The preliminary magnitude derived for that source is:
r = 21.55
Further observations and analysis are ongoing.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
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 43834
Subject
GRB 260225A: SVOM/VT optical upper limits
Date
2026-02-25T16:35:56Z (13 days ago)
Edited On
2026-03-01T23:55:17Z (9 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, C. Wu, Y. N. Ma, Z. H. Yao, Y. L. Qiu, L. P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) and L. Zhang (IHEP) report on behalf of the SVOM/VT team.
SVOM/VT performed observation with auto slew to the field of GRB 260225A triggered by SVOM/ECLAIRs (sb26022501, Ma et al., GCN 43829). The observation started at 2026-02-25T09:38:31 UTC, i.e. about 47.68 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
No bright uncatalogued sources were detected within the error box of ECLAIRs (Ma et al., GCN 43829), compared to the Legacy survey catalog, down to 22.0 mag in VT_R. This non-detection is consistent with the result from COLIBRÍ (Basa et al., GCN 43830).
More detailed analysis is still on going.
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 43830
Subject
GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
Date
2026-02-25T13:15:27Z (13 days ago)
From
Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr>
Via
Web form
Stéphane Basa (UAR Pytheas), Diego López-Cámara (UNAM), Benjamin Schneider (LAM), Damien Dornic (CPPM), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), and L. Zhang (IHEP) report:
We imaged the field of GRB 260225A (Ma et al., GCN Circ. 43829) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-02-25 09:02 UTC to 10:24 UTC (from 0.18 to 1.57 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r and z filters.
The data were reduced and analyzed with the COLIBRÍ ASU pipeline, and also analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the Pan-STARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
Within the ECLAIRs 5.1 arcmin error circle and in comparison to the corresponding LS catalog and images, we do not detect any new sources to preliminary 5-sigma limiting magnitudes of:
r > 24.1
z > 22.5.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
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 43829
Subject
GRB 260225A: SVOM detection of a burst
Date
2026-02-25T09:40:51Z (13 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Yinuo Ma (NAOC), Li Zhang (IHEP), Nicolas Dagoneau (CEA), Frédéric Daigne (IAP), Pierre Maggi (ObAS), report on behalf of the SVOM mission team:
At 2026-02-25T08:51:15 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260225A (SVOM burst-id sb26022501).
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. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 16.32 in the [8-120] keV energy band over a time window of 40.96 seconds starting at 2026-02-25T08:50:57.
The localization of the best alert is R.A., Dec. 204.6748, 44.6546 degrees:
R.A. (J2000) = 13h38m41.95s
Dec. (J2000) = 44d39m16.67s
with a 90% confidence level (C.L.) radius of 5.13 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst was also detected by SVOM/GRM with a significance of 4.90.
SVOM slewed to the burst.
No X-ray observation could be performed by SVOM/MXT for the time being, due to Earth occultation.
SVOM/VT observations will be reported in 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 zhangli: zhangli@ihep.ac.cn.
Please contact the BA by email if you require additional information.