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

[vsnet-grb-info 41989] GRB 260225A: SVOM/VT optical continued observations and upper limit
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43872 SUBJECT: GRB 260225A: SVOM/VT optical continued observations and upper limit DATE: 26/02/28 05:02:37 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41988] GRID detection of GRB 260223A
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43871 SUBJECT: GRID detection of GRB 260223A DATE: 26/02/28 04:46:33 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> GRID detection of GRB 260223A Longhao Li, Xinyu Liu, Chenyu Wang report on behalf of the GRID Collaboration: GRID-11B reports the detection of the long-duration GRB 260223A, which was also detected by Fermi GBM (GCN Circular 43808), MASTER-OAFA (GCN Circular 43809), BALROG (GCN Circular 43810), DDOTI (GCN Circular 43811), COLIBRÍ(GCN Circular 43812), SVOM (GCN Circular 43815), Glowbug (GCN Circular 43824) The event was triggered with GRID on 2026-02-23 at 04:11:09 UTC. The measured burst duration (T90) in the 30-2000 keV range is approximately 22.2 +/- 3.0 seconds. The GRID light curve of this event can be found at [GRID_GRB260223A_ltcv.pdf](https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260223A/GRID_GRB260223A_ltcv.pdf). GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41987] EP260227a: Global MASTER-Net observations report
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43870 SUBJECT: EP260227a: Global MASTER-Net observations report DATE: 26/02/28 04:45:41 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP260227a ( EP Team et al., GCN 43869) errorbox 14883 sec after trigger time at 2026-02-28 00:20:32 UT, with upper limit up to 21.0 mag. The observations began at zenith distance = 42 deg. The sun altitude is -44.5 deg. The galactic latitude b = 41 deg., longitude l = 345 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3160292 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.27s , -11d 34m 27.7s) | C | 60 | 19.3 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 420 | 20.1 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 1620 | 21.0 | 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 60 | 19.2 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 46.0s) | C | 420 | 20.0 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 17.70s , -11d 18m 51.8s) | C | 1620 | 20.7 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 50m 17.85s , -11d 34m 01.7s) | C | 60 | 19.3 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 48m 24.61s , -11d 18m 21.0s) | C | 60 | 19.2 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 50m 14.69s , -11d 32m 38.3s) | C | 60 | 19.3 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 48m 21.41s , -11d 16m 58.1s) | C | 60 | 19.2 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 50m 10.29s , -11d 34m 21.4s) | C | 120 | 19.7 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 48m 17.24s , -11d 18m 39.5s) | C | 120 | 19.6 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 50m 16.17s , -11d 34m 15.7s) | C | 120 | 19.7 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 48m 23.05s , -11d 18m 34.8s) | C | 120 | 19.6 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 120 | 19.8 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 360 | 20.2 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 120 | 19.7 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 360 | 20.1 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 50m 14.08s , -11d 33m 59.3s) | C | 120 | 19.8 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 48m 20.83s , -11d 18m 19.0s) | C | 120 | 19.6 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 50m 18.07s , -11d 32m 38.9s) | C | 120 | 19.8 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 48m 24.76s , -11d 16m 58.8s) | C | 120 | 19.7 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 120 | 19.8 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 600 | 20.2 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.5s) | C | 120 | 19.7 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.4s) | C | 600 | 20.2 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 50m 10.14s , -11d 32m 11.3s) | C | 120 | 19.8 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 48m 16.73s , -11d 16m 31.1s) | C | 120 | 19.7 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 840 | 20.2 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 840 | 20.2 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 50m 11.91s , -11d 34m 07.5s) | C | 120 | 19.8 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 48m 18.35s , -11d 18m 26.9s) | C | 120 | 19.8 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 360 | 20.2 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 360 | 20.1 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 50m 14.06s , -11d 32m 19.1s) | C | 120 | 19.8 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 48m 20.45s , -11d 16m 38.4s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 50m 14.01s , -11d 33m 49.8s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 48m 20.41s , -11d 18m 08.7s) | C | 120 | 19.8 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 360 | 20.2 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.04s , -11d 16m 28.0s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.05s , -11d 16m 27.9s) | C | 360 | 20.2 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 50m 10.38s , -11d 32m 57.2s) | C | 120 | 19.9 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 48m 16.83s , -11d 17m 15.8s) | C | 120 | 19.8 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 48m 18.27s , -11d 16m 14.0s) | C | 120 | 19.9 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 50m 11.81s , -11d 31m 55.4s) | C | 120 | 19.8 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 120 | 19.9 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 600 | 20.2 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.2s) | C | 120 | 19.8 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.1s) | C | 600 | 20.3 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 48m 16.38s , -11d 18m 08.8s) | C | 120 | 19.9 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 50m 10.00s , -11d 33m 50.7s) | C | 120 | 19.9 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 48m 23.93s , -11d 17m 39.4s) | C | 120 | 19.8 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 50m 17.58s , -11d 33m 21.1s) | C | 120 | 19.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41986] EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43869 SUBJECT: EP260227a: Einstein Probe detection of an X-ray transient and refined analysis DATE: 26/02/28 04:28:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO), H. C. Ding, T, Wu, Y. J. Yi (BNU), W. F. Wen (SZTU), Z. X. Ling(NAOC) 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 EP260227a. The transient triggered EP-WXT (ID: 01709258681) at 2026-02-27T20:12:29 (UTC). The WXT position of the source is R.A. = 223.101 deg, DEC = -11.408 deg (J2000) with an uncertainty of 2.586 arcmin in radius (90% C.L. statistical and systematic). The refined analysis of the WXT data shows that the event started at T0=2026-02-27T19:58:52 (UTC), and lasted for approximately 250 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 9.3×10^20 cm^-2 and a photon index of 0.8 (-0.6/+0.6). The derived average unabsorbed 0.5-4 keV flux is 4.1 (-1.3/+1.7) × 10^(-10) erg/s/cm^2. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 223.1002 deg, DEC = -11.386 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.8 (-0.1/+0.1) × 10^21 cm^-2, and a photon index of 1.5 (-0.3/+0.3). The derived average unabsorbed 0.5-10 keV flux is 8.3 (-0.9/+1.2) ×10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The optical counterpart was reported by Eyles-Ferris et al. (GCN 43867) and Li et al. (GCN 43868). 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/43869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41985] The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43868 SUBJECT: The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart DATE: 26/02/28 02:12:37 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), Runduo Liang (NAOC), David Sand (U of Arizona) We observed the position of the EP-WXT trigger 01709258681 (EP260227a?) with a Las Cumbres 1m telescope at Siding Spring Observatory 2.6 hours after the Einstein Probe WXT trigger and again 4 hours after the trigger. We took 2x300s exposures in each visit in the broad optical w band. We find a rapidly fading source consistent with the position reported by Eyles-Ferris et al. (GCN 43867) and measure the following preliminary photometry calibrated to the r band: Epoch 1: MJD 61098.954 Mag 20.28 ± 0.09 Epoch 2: MJD 61099.011 Mag 21.08 ± 0.10 View this GCN Circular online at https://gcn.nasa.gov/circulars/43868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41984] EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43867 SUBJECT: EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow DATE: 26/02/27 23:33:12 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> R. A. J. Eyles-Ferris (Leicester), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. N. D. van Dalen (Radboud), J. Chacón (PUC), report on behalf of a larger collaboration: We observed the field of the EP/WXT trigger 01709258681 (likely EP260227a) using the Sinistro instrument on the 1-m telescope in Sutherland (South Africa), part of the LCO network. Six 300 s observations were secured in the SDSS r band, with mean time 2026 Feb 27.945 UT (2.47 hr after the WXT trigger). Comparison of our images with archival templates from the Legacy Survey reveals a new object at coordinates (J2000): RA = 14:52:19.94 Dec = -11:24:23.9 Photometry yields r = 20.18 +/- 0.04 (AB) calibrated against nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction. We suggest this is the optical counterpart of the EP/WXT trigger 01709258681. View this GCN Circular online at https://gcn.nasa.gov/circulars/43867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41983] IceCube cascade alert 142200_1517143 retraction
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43866 SUBJECT: IceCube cascade alert 142200_1517143 retraction DATE: 26/02/27 20:54:47 GMT FROM: Erik Blaufuss at University of Maryland, College Park <blaufuss(a)umd.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 27 Feb 26 01:26:48 UT IceCube issued a cascade alert (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/142200_1517143.amon) reporting the detection of a neutrino candidate event with a high probability of being of astrophysical origin. Upon further examination by the IceCube collaboration, the event was found to be likely due to unintended light emission from detector equipment. At the time of this alert, portions of the detector hardware were found to unintentionally producing light in the instrumented volume. Normally, these periods of operation should be excluded from generating alerts. We apologize for any confusion this error may have caused. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/43866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41982] GRB 260226A: Insight-HXMT/HE detection of the very bright burst
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43865 SUBJECT: GRB 260226A: Insight-HXMT/HE detection of the very bright burst DATE: 26/02/27 16:11:28 GMT FROM: yzh807926(a)163.com Zheng-Hang Yu, Chen-Wei Wang and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-02-26T10:38:11.100 (T0), Insight-HXMT/HE detected the long bright burst GRB 260226A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43840), Fermi/LAT(D. Depalo et al., GCN #43844) , AstroSat-CZTI (Harsha et al., GCN #43846), Glowbug (Woolf et al., GCN #43855), CALET-GBM (Kobayashi et al., GCN #43860), and Konus-Wind(D. Svinkin et al., GCN #43864) The Insight-HXMT/HE light curve mainly consists of two eposides with a T90 of about 76 s. The 1s peak rate, measured from T0+1.5 s, is 15858 cnts/sec. Insight-HXMT/HE detected a total of 264251 counts form this burst. However, the HE detector was suffered from saturation during the brightest peak due to the high-brightness. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260226A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41981] Konus-Wind detection of GRB 260226A
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43864 SUBJECT: Konus-Wind detection of GRB 260226A DATE: 26/02/27 13:52:56 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The bright, long-duration GRB 260226A (Fermi-GBM detection: The Fermi GBM team, GCN 43840; Bissaldi eat al., GCN 43851; BALROG localization: Preis and Greiner, GCN 43843; Fermi-LAT detection: Depalo et al., GCN 43844, 43850; AstroSat-CZTI detection: Harsha et al., GCN 43846; NuSTAR-ACS detection: Waratkar et al., GCN 43854; Glowbug detection: Woolf et al., GCN 43855; CALET-GBM detection: Kobayashi et al., GCN 43860) triggered Konus-Wind at T0=38287.440 s UT (10:38:07.440). The burst light curve shows a very bright, multi-peaked emission pulse which starts at ~T0-9 s and has a duration of ~30 s. This pulse is followed by a weaker, smoothly decaying emission tail, visible up to the end of the KW triggered data record (~T0+250 s). The emission is seen up to ~20 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260226_T38287/ As observed by Konus-Wind, the burst had the total fluence of 7.27(-0.17,+0.17)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+10.688 s, of 1.33(-0.06,+0.06)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+142.080 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.93(-0.02,+0.03), the high energy photon index beta = -2.33(-0.07,+0.06), the peak energy Ep = 613(-25,+26) keV (chi2 = 118/97 dof). The spectrum near the maximum count rate (measured from T0+10.240 to T0+10.752 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.64(-0.06,+0.07), the high energy photon index beta = -2.11(-0.08,+0.07), the peak energy Ep = 772(-77,+80) keV (chi2 = 48/57 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/43864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41980] GRB 260223A: 7DT detection and Medium-band SED of Afterglow
by GCN Circulars 27 Feb '26

27 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43863 SUBJECT: GRB 260223A: 7DT detection and Medium-band SED of Afterglow DATE: 26/02/27 12:05:22 GMT FROM: YoungPyo Hong at Seoul National University <evan77333(a)gmail.com> YoungPyo Hong (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Donggeun Tak (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Donghwan Hyun (SNU ARC/SNU), Gregory S.H. Paek (IfA, SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), Ji Hoon Kim (SNU ARC/SNU), and Won-Hyeong Lee (SNU ARC/SNU), report on behalf of the 7 Dimensional Telescope (7DT) team: We report optical follow-up observations of GRB26023A (GCN 43808; GCN 43809), conducted with the 7-Dimensional Telescope (7DT), located in Chile. The 7DT follow-up began at 04:44:14 UTC on 2026-02-23, corresponding to T0 + 33 minutes, pointing to a region covering the target localization provided by Fermi (GCN 43808) at RA, DEC = 110.5 deg, -29.4 deg with an uncertainty of 1.7 degree. Initial observations were made with 15, units in 19 medium-band filters as well as r-band filters (20 filters in total). The following table summarizes the observations and the derived 5-sigma upper limits: Filter Mag Mag_err Exposure Date Time ---------------------------------------------------------------------------------------------------- r 19.05 0.08 300.0 2026-02-23T04:49:44.000 m400 >19.02 N/A 300.0 2026-02-23T04:44:14.000 m425 19.28 0.16 300.0 2026-02-23T04:44:31.667 m450 19.48 0.24 300.0 2026-02-23T04:44:16.667 m475 18.97 0.12 300.0 2026-02-23T04:44:15.000 m500 19.62 0.27 300.0 2026-02-23T04:44:20.667 m525 19.48 0.24 300.0 2026-02-23T04:44:23.000 m550 >19.29 N/A 300.0 2026-02-23T04:49:38.000 m575 18.95 0.14 300.0 2026-02-23T04:51:58.000 m600 18.92 0.20 300.0 2026-02-23T04:49:39.333 m625 18.79 0.22 300.0 2026-02-23T04:49:37.000 m650 18.66 0.22 300.0 2026-02-23T04:44:38.000 m675 >18.95 N/A 300.0 2026-02-23T04:44:23.000 m700 18.13 0.18 300.0 2026-02-23T04:44:18.000 m725 >18.46 N/A 300.0 2026-02-23T04:44:23.000 m750 18.23 0.22 300.0 2026-02-23T04:44:20.667 m775 17.99 0.31 300.0 2026-02-23T04:44:43.333 m800 >17.52 N/A 300.0 2026-02-23T04:44:21.667 m825 >17.41 N/A 300.0 2026-02-23T04:44:21.333 m850 >17.05 N/A 300.0 2026-02-23T04:44:21.000 ---------------------------------------------------------------------------------------------------- * Upper limits (marked with '>') are 5-sigma limits The optical counterpart was detected in most filters. Photometric flux calibration was performed using synthetic photometry based on the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. Note that no extinction correction has been applied. The 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at https://7ds.snu.ac.kr/ and http://gwuniverse.snu.ac.kr/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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