- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41955] GRB260225A: SVOM/ECLAIRs refined position
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43841 SUBJECT: GRB260225A: SVOM/ECLAIRs refined position DATE: 26/02/26 11:19:51 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> 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) View this GCN Circular online at https://gcn.nasa.gov/circulars/43841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41954] GRB 260226A: Fermi GBM Final Real-time Localization
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43840 SUBJECT: GRB 260226A: Fermi GBM Final Real-time Localization DATE: 26/02/26 10:48:46 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 10:37:55 UT on 26 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260226A (trigger 793795080.95811 / 260226443). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 45.3, Dec = 15.7 (J2000 degrees, equivalent to J2000 03h 01m, 15d 41'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 17.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260226443/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41953] GRB 260225A: EP-FXT follow-up observation
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43839 SUBJECT: GRB 260225A: EP-FXT follow-up observation DATE: 26/02/26 04:07:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/43839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41952] GRB 260225A: SVOM/VT optical observation
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43838 SUBJECT: GRB 260225A: SVOM/VT optical observation DATE: 26/02/26 03:29:53 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41951] GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43837 SUBJECT: GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate DATE: 26/02/26 00:08:25 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41950] GCN Announcement: Passing of Scott Barthelmy, GCN Founder
by GCN Announcements 25 Feb '26

25 Feb '26

With heavy hearts, we report that our colleague and mentor Scott Barthelmy passed away on February 25, 2026. Scott was the founder, architect, and tireless maintainer of GCN from its inception in 1993 until his retirement (see history of GCN; https://gcn.nasa.gov/docs/about/history) Scott was supportive of the development of the new GCN, and we have always aimed to honor his legacy and service to our community. As PI of the Swift-BAT and Swift Project Scientist, he had exceptional impacts on our field. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41949] GRB 260225C: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43836 SUBJECT: GRB 260225C: Fermi GBM Final Real-time Localization DATE: 26/02/25 19:08:07 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 18:55:39 UT on 25 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260225C (trigger 793738544.90425 / 260225789). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 102.6, Dec = 69.3 (J2000 degrees, equivalent to J2000 06h 50m, 69d 17'), with a statistical uncertainty of 15.2 degrees. The angle from the Fermi LAT boresight is 54.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260225789/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260225789/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260225789/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41948] GRB 260223A: Fermi GBM Observation
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43835 SUBJECT: GRB 260223A: Fermi GBM Observation DATE: 26/02/25 17:16:57 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 04:11:09.81 UT on 23 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260223A (trigger 793512674/260223174), which was also detected by DDOTI (Becerra et al. 2026, GCN 43811), COLIBRI (de Ugarte Postigo et al. 2026, GCNs 43812, 43814 & 43820), SVOM/GRM (Wang et al. 2026, GCN 43815), SVOM/VT (Li et al. 2026, GCN 43816) and Glowbug (Woolf et al. 2026, GCN 43824). The Fermi GBM on-ground location (GCN 43808) is consistent with the DDOTI position. The angle from the Fermi LAT boresight is 33 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 39 s (50-300 keV). The time-averaged spectrum from T0-9.2 to T0+51.2 s is best fit by a Band function with Epeak = 70 +/- 6 keV, alpha = -0.76 +/- 0.09, and beta = -1.91 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (2.16 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+18 s in the 10-1000 keV band is 10.4 +/- 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41947] GRB 260225A: SVOM/VT optical upper limits
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43834 SUBJECT: GRB 260225A: SVOM/VT optical upper limits DATE: 26/02/25 16:35:56 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> 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 260226A 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 the 3 sigma limit of VT_R ~ 22.0 mag. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41946] GRB 260225B: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43833 SUBJECT: GRB 260225B: Fermi GBM Final Real-time Localization DATE: 26/02/25 15:24:47 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 15:14:07 UT on 25 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260225B (trigger 793725252.479854 / 260225635). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 326.4, Dec = 0.9 (J2000 degrees, equivalent to J2000 21h 45m, 0d 54'), with a statistical uncertainty of 1.8 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/bn260225635/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260225635/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260225635/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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