February 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41959] EP260214a: VLA 6 GHz detection
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43845 SUBJECT: EP260214a: VLA 6 GHz detection DATE: 26/02/26 14:15:11 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> R. Ricci, M. Yadav, Y.-H. Yang, N. Passaleva and E. Troja (U Rome) report: We observed the Einstein Probe event EP260214a detected by EP/WXT (A. Li et al. GCN 43742) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz on Feb 21st 2026, 6.6 days after the trigger. Within the EP/FXT error circle (A. Li et al., GCN 43751) we detect a possible radio counterpart at RA, Dec (J2000) = 13:24:55.401, -29:02:32.97 with a flux density of about 60 uJy. No source is visible at this position in our deep VLT/HAWKI image (N. Passaleva et al. GCN 43756). However, we note that the candidate counterpart lies 8.8” away from a bright galaxy (r=19.62 AB mag), corresponding to a chance alignment of Pcc~4% (Bloom et al. 2002). Assuming a photometric redshift of z=0.18±0.15 (PRLS, Zhou et al. 2021), this corresponds to a projected physical offset of 27 (+15, -22) kpc. Further observations to assess the variability of the candidate radio counterpart are planned. We thank the VLA staff for executing the observations View this GCN Circular online at https://gcn.nasa.gov/circulars/43845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41958] GRB 260226A: Fermi-LAT detection of a bright burst
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43844 SUBJECT: GRB 260226A: Fermi-LAT detection of a bright burst DATE: 26/02/26 13:34:45 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo(a)ba.infn.it> D. Depalo (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), S. Zhu (DESY), R. Gupta (NASA/GSFC), J. L. Racusin (NASA/GSFC), F. Longo (Univ and INFN Trieste) report on behalf of the Fermi-LAT Collaboration: At 10:38:18.84 UT on Feb 26, 2026, Fermi-LAT triggered on high-energy emission from GRB 260226A, also detected by GBM (trigger 793795080.95811 / 260226443, GCN Circular 43840) at 10:37:55 UT. Note that this is a rare onboard detection seeded by LAT, independent of the GBM trigger, which is why the trigger times differ. LAT-seeded alerts have a very high threshold and this is only the second GRB to have passed this alert after GRB 090510. The onboard location is RA, Dec 42.050, +8.033 with an approximate error radius of 0.5 deg (90% containment, systematic error only). This was 17 deg from the LAT boresight at the time of the trigger. We anticipate providing a refined location within the next 12 hours when the LAT science data for this burst are downlinked and processed. The Fermi-LAT point of contact for this burst is Niccolò Di Lalla (niccolo.dilalla(a)stanford.edu) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41957] GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43843 SUBJECT: GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443) DATE: 26/02/26 13:23:46 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 793795080 at 10:37:55 on 26 Feb. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 43.6 deg Decl.(2000.0) = 9.6 deg The 1 sigma statistical error radius is 0.2 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260226443/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260226443/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260226443/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41956] EP260224a: LCO optical upper limits
by GCN Circulars 26 Feb '26

26 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43842 SUBJECT: EP260224a: LCO optical upper limits DATE: 26/02/26 12:00:50 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), A. van Hoof (Radboud), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), and A. J. Levan (Radboud) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260224a (Yang et al., GCN 43828) using LCO 1m telescopes located at the Cerro Tololo Inter-American Observatory (Chile) and the South African Astronomical Observatory (South Africa) equipped with the SINISTRO instrument. A series of 6x300 s exposures were taken in each of the SDSS-r and SDSS-z filters, starting at 2026-02-26 03:25:00 UT (32.4 hr after the trigger) and 2026-02-25 23:23:55 UT (30.3 hr after the trigger) respectively. We performed subtractions on our stacked images using a template image from the KMTNet Synoptic Survey of the Southern Sky (Kim et al. 2016, doi:10.5303/JKAS.2016.49.1.37) and compared the stacks and template manually. No new source is detected within or at the border of the EP/WXT uncertainty region (Yang et al., GCN 43828). From the stacked images, we obtain the following 3-sigma upper limits:  r > 23.6 z > 21.6 These upper limits are in AB magnitudes, calibrated using nearby stars from the SkyMapper catalog, and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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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