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

[vsnet-grb-info 41945] EP260126a: VLA 6 GHz detection
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43832 SUBJECT: EP260126a: VLA 6 GHz detection DATE: 26/02/25 15:06:53 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> R. Ricci, M. Yadav, E. Troja, N. Passaleva and Y.-H. Yang (U Rome) report: We observed the Einstein Probe event detected by EP/WXT (S.F. Fu et al. GCN 43520) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz in two epochs on Jan 29th 2026 (3.3 days after the trigger) and Feb 19th 2026 (24.1 days after the trigger). Within the EP/FXT localization (S.F Fu et al., GCN 43526), we detect two radio sources, however only one shows a significant rebrightening between the two epochs. We therefore propose that this source, located at RA, DEC(J2000) = 06:55:01.01, +37:42:18.68, is the radio counterpart of EP260126A. At this position, Legacy Survey DR10 (Dey et al. 2019) images show a faint object (r~24 AB mag), which we suggest as the putative host galaxy of the EP transient. Further observations are planned. We thank the VLA staff for executing the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41944] EP260223a: Liverpool Telescope upper limits
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43831 SUBJECT: EP260223a: Liverpool Telescope upper limits DATE: 26/02/25 14:09:47 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and N. Habeeb (Leicester) report on behalf of a larger collaboration: We observed the field of EP260223a (Liu et al., GCN 43817) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 8x200s exposures in the SDSS r’ and 9x200s exposures in the SDSS z’ filters starting at 2026-02-24 21:07:44 UT, approximately 33.8 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and also compared the stacked and reference images manually. Within the EP/WXT localisation (Liu et al., GCN 43817), we detect no new sources in our stacked images consistent with the results of Álvarez et al. (GCN 43818) and Zhu et al. (GCN 43826). This is also consistent with the fast fading X-ray emission implied by Liu et al. (GCN 43822). We derive 3-sigma upper limits of r’ > 22.9 and z’ > 22.6 for our stacked images. View this GCN Circular online at https://gcn.nasa.gov/circulars/43831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41943] GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43830 SUBJECT: GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits DATE: 26/02/25 13:15:27 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41942] GRB 260225A: SVOM detection of a burst
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43829 SUBJECT: GRB 260225A: SVOM detection of a burst DATE: 26/02/25 09:40:51 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> 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(a)ihep.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41941] EP260224a: Einstein Probe detection of an X-ray transient
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43828 SUBJECT: EP260224a: Einstein Probe detection of an X-ray transient DATE: 26/02/25 09:01:39 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: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260224a. The transient triggered EP-WXT at 2026-02-24T17:03:42 (UTC). The WXT position of the source is R.A. = 175.200 deg, DEC = -41.415 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) started at 2026-02-25T06:21:59 (UTC), approximately 13 hours after the WXT trigger. No onboard alert was generated by FXT during this observation. Further follow-up observations are encouraged. 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/43828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41940] EP 260225.148: COLIBRÍ Confirmation of flaring star
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43827 SUBJECT: EP 260225.148: COLIBRÍ Confirmation of flaring star DATE: 26/02/25 06:39:13 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa(a)lam.fr> Diego López-Cámara (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), 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), Asuka Kuwata (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We automatically observed the field of EP-WXT trigger 01709258631 (Lui et al., GCN Circ. 43817) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-25 04:42 to 05:54 UTC (from 1.16 to 2.36 hours after the trigger) and obtained 55 minutes of simultaneous exposure in the 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 Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We used STDWeb (Karpov 2025) to perform image subtraction against Legacy Survey DR10 templates (Dey et al. 2019). We do not detect any new source in the WXT uncertainty region down to the following 5-sigma limits: r > 23.4 z > 22.4 Our observation supports that EP-WXT trigger 01709258631 is very probably due to a flaring star as announced by Cao et al. (GCN Circ. 4382517). 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/43827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41939] EP260223a: Xinglong optical upper limit
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43826 SUBJECT: EP260223a: Xinglong optical upper limit DATE: 26/02/25 06:29:12 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Yinan-Zhu (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Yuguang-Sun (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration: Following the detection of EP260223a (GCN Circular 43817), we observed the field of EP260223a using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s N-band frames by using 2.16-m with a median time of 2026-02-24 10:56:45 (UT), 4 hrs after the EP trigger and 3x300s clear-band frames by using 2.16-m with a median time of 2026-02-21T19:09:10, 8 hrs after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 20 arcsec EP/FXT error circle (GCN Circular 43817), down to 3-sigma limiting magnitudes of N-band ~19.11 mag for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41938] The EP-WXT trigger 01709258631 is likely a flaring star
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43825 SUBJECT: The EP-WXT trigger 01709258631 is likely a flaring star DATE: 26/02/25 06:09:06 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> JiaYing Cao(IHEP), WenFeng Wen(SZTU), Guojiong Yang and Haiwu Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709258631 at 2026-02-25T03:33:22 is likely a stellar flare associated with RX J1220.4+1226. The estimated flux of the flare is around 4e-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4e+31 erg/s. 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/43825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41937] GRB 260223A: Glowbug gamma-ray detection
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43824 SUBJECT: GRB 260223A: Glowbug gamma-ray detection DATE: 26/02/25 05:26:59 GMT FROM: Richard S. Woolf at US Naval Research Laboratory <richard.s.woolf.civ(a)us.navy.mil> R. Woolf, C.C. Cheung, 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 260223A, which was also detected by Fermi GBM (GCN 43808) and SVOM/GRM (GCN 43815). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-23 04:11:09.520 with a duration of 20.5 s and a total significance of about 48.4 sigma. Following the initial event onset, the light curve comprises two main peaks at ~T0+11s and +18s. Note that data from ~T0+15s to T0+17s suffered from deadtime in various detectors. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41936] EP260213a: Mephisto optical upper limits
by GCN Circulars 25 Feb '26

25 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43823 SUBJECT: EP260213a: Mephisto optical upper limits DATE: 26/02/25 04:33:50 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Guowang Du, Ziwei Li, Zhenfei Qin, Jialong Zhou, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at the Lijiang Observatory, was triggered at 2026-02-13T20:05:57 (~7.2 min after the EP/WXT trigger) to observe the field of EP260213a (Yang et al., GCN 43729; Li et al., GCN 43730). A set of simultaneous multi-band (ugi and vrz) images was collected. In our stacked frames, no new candidate was detected within the EP/FXT localization (Li et al., GCN 43730) and the upper limits (3 sigma) are listed below. These results are consistent with previously reported non-detection by Cotter et al. (GCN 43728), Wu et al. (GCN 43731), Maksut et al. (GCN 43732), Pankov et al. (GCN 43733), Li et al. (GCN 43734), Aryan et al. (GCN 43735), Fortin et al. (GCN 43737), Lipunov et al. (GCN 43738) and Eyles-Ferris et al. (GCN 43739). --------------------------------------------------- Start_Time(UT) | Band | Exp(s) | LimMag (AB) --------------------------------------------------- 2026-02-13T20:11:30 | u | 45.0*8 | >22.68 2026-02-13T20:05:57 | v | 45.0*5 | >22.62 2026-02-13T20:11:33 | g | 45.0*8 | >23.51 2026-02-13T20:05:59 | r | 45.0*5 | >23.41 2026-02-13T20:13:07 | i | 45.0*8 | >22.84 2026-02-13T20:05:59 | z | 45.0*5 | >21.85 --------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. The facility is operated by the South-Western Institute for Astronomy Research (SWIFAR), Yunnan University. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025 and presently, these are under the commissioning phase. All the data have been reduced by the Mephisto data processing pipeline. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher. View this GCN Circular online at https://gcn.nasa.gov/circulars/43823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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