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[vsnet-grb-info 42500] GRB 260412A: SVOM/ECLAIRs refined analysis
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44378 SUBJECT: GRB 260412A: SVOM/ECLAIRs refined analysis DATE: 26/04/21 13:31:47 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Marius Brunet (IRAP), Wenjin XIE (NAOC), Olivier Godet (IRAP), Ziqi Wang (GXU), Zhiyong Liu(GZNU) 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 260412A (SVOM burst-id sb26041206 – GCN 44276, trigger time T0 = 2026-04-12T06:13:35 UTC), which was also detected by Fermi (GCN 44275, 44279), GECAM (GCN 44281) and HXMT (GCN 44294). The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve with late peaks at around T0+80s and T0+160s. The burst duration is T90 = 165.0 +2.6/-1.6 s in the 4-120 keV energy band. The time-averaged spectrum from T0-3.5 s to T0+200.5 s in the energy range 4-120 keV is best fitted by a powerlaw model with best-fit parameters – alpha = -1.5 +/-0.3. With this model, the 4-120 keV fluence is 7.4 +/- 0.3 e-6 erg/cm^2. Using the same Fermi/GBM time window as in Palafox et al. (GCN 44279), we retrieve a consistent photon index value when using a cutoff model and fixing Epeak at 210 keV. 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) View this GCN Circular online at https://gcn.nasa.gov/circulars/44378. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42499] GRB 260421B: SVOM/VT optical observations
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44377 SUBJECT: GRB 260421B: SVOM/VT optical observations DATE: 26/04/21 11:53:36 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, C. Wu, L. P. Xin, Y. L. Qiu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), W. L. Zhang (PMO), Z. Y. Liu (GZNU) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic slew to the field of GRB 260421B triggered by SVOM/ECLAIRs (sb26042105, Zhao et al., GCN 44362). This burst was also detected by SVOM/GRM (Zhao et al., GCN 44362), SVOM/MXT (Zhao et al., GCN 44362), and Fermi-GBM (Fermi GBM team, GCN 44360; Preis & Greiner, GCN 44361). The observation started at 2026-04-21T04:18:32 UTC, i.e., approximately 5.1 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart (He et al., GCN 44363; Sanchez-Alvarez, GCN 44364; Turpin et al., GCN 44365; Wu et al., GCN 44366) with redshift z=2.115 (Schneider et al., GCN 44368) was clearly detected in single frames in both channels. With X-band data available，the light curves showed a fast decay from 5.5 minutes to 50 minutes post trigger, following a plateau after 3.37 hours. The preliminary measurements are given in the AB magnitudes and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 5.53 min VT_B 50 sec 16.23+/-0.03 mag 5.53 min VT_R 50 sec 15.77+/-0.03 mag 3.599 hr VT_B 27*100 sec 20.94+/-0.07 mag 3.668 hr VT_R 22*100 sec 20.52+/-0.06 mag 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/44377. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42498] EP260416a: J band upper limit by SYSU 80cm infrared telescope
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44376 SUBJECT: EP260416a: J band upper limit by SYSU 80cm infrared telescope DATE: 26/04/21 11:00:51 GMT FROM: lijj328(a)mail2.sysu.edu.cn Jin-Ji Li, Hao-Nan Yang, Chun Chen, Duo-Le Cao, Zhong-Nan Dong, Rui-Chen Gao, Wei-Sen Huang, Jia-Qi Lin, Pu Lin, Yun Shi, Yan Yu, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of the fast X-ray transient EP260416a (Hu et al., GCN 44307) using the Sun Yat-sen University (SYSU) 80cm infrared telescope. Our observations were carried out on 2026 Apr 19 18:39 UT, 85.1 hours after the trigger, using stacked images in the J band. We do not detect any counterpart at the position of the optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334, He et al. GCN 44336, An et al. GCN 44339, Jelinek et al. GCN 44341; Guziy et al., GCN 44351; Ho et al., GCN 44354), down to a 5-sigma depth of J ~ 18.1 Vega magnitudes. The SYSU 80 cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44376. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42497] GRB 260310A: Late-time Chandra X-ray Detection
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44375 SUBJECT: GRB 260310A: Late-time Chandra X-ray Detection DATE: 26/04/21 10:40:36 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Yu-Han Yang (U Rome), Eleonora Troja (U Rome), Yi-Han Iris Yin (HKU), Brendan O’Connor (CMU), Muskan Yadav (U Rome), Niccolo’ Passaleva (U Rome), Roberto Ricci (U Rome) report: We imaged the field of GRB 260310A (Fermi GBM team, GCN 43951,43975; AstroSat CZTI collaboration, GCN 43958) with the Chandra X-ray Observatory via a Director’s Discretionary Time (DDT) request (PI: Yang). Observations started at 2026-04-20T01:47:42 (~41 days after the trigger) using the ACIS-S instrument with a total exposure time of ~5 ks. Three sources are detected within a 1-arcmin radius centered on the optical counterpart (O’Neill et al. 2026, TNS Discovery Report 294132). The target afterglow is clearly identified with 89 counts, while two neighboring sources are marginal contributors, yielding only 5 and 9 counts, respectively. We performed a preliminary spectral analysis of the afterglow in the 0.5–8 keV range, adopting an absorbed power-law model with a fixed galactic absorption (N_H = 2.59e20/cm2) and intrinsic absorption (N_Hz = 1.7e21/cm2). We find a photon index of 2.07 ± 0.25 and a corresponding unabsorbed flux of (5.9+/-0.8)e-13 ergs/cm2/s (0.3-10 keV). Our observations confirm that the X-ray rebrightening (Jayaraman et al., GCN 44234; Waratkar et al.; GCN 44278) is intrinsic to the GRB afterglow and not contributed by nearby sources. Our temporal analysis indicates that the light curve is consistent with a late-time bump which is currently transitioning into a decay phase. We thank the Chandra director, Pat Slane, for awarding discretionary time and the observatory staff for rapidly scheduling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44375. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42496] GRB 260418A: Insight-HXMT/HE detection
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44374 SUBJECT: GRB 260418A: Insight-HXMT/HE detection DATE: 26/04/21 10:34:05 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-18T04:49:35.000 (T0), Insight-HXMT/HE detected a short burst, GRB 260418A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44335). The Insight-HXMT/HE light curve mainly consists of a single pulse with a duration (T90) of 0.30 +0.55/-0.10 s. The 1s peak rate, measured from T0-0.475 s, is 361 cnts/sec. Insight-HXMT/HE detected a total of 292 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260418A.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/44374. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42495] EP260416a: 1.3m DFOT optical observation
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44373 SUBJECT: EP260416a: 1.3m DFOT optical observation DATE: 26/04/21 10:02:49 GMT FROM: pawarpankaj1492(a)gmail.com Pankaj Pawar, Anshika Gupta, Debalina Kar, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of EP260416a (Hu et al., GCN 44307) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of observational sciencES (ARIES), India. The observations began on 2026-04-20 at 15:58:17 UT, approximately ~106 hours after the trigger. We obtained a series of 300s exposures in the R filter. The frames were aligned and stacked to improve the signal-to-noise ratio. The optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334; He et al. GCN 44336; An et al. GCN 44339; Jelinek et al. GCN 44341; Guziy et al., GCN 44351; and Ho et al., GCN 44354) was not detected in the stacked image. The details of observations and measured upper limit are as follows: Date (UT) Start Time T_start-T0 (days) Filter Exposure (s) Magnitude (AB) ======================================================================================= 2026-04-20 15:58:17 ~4.44 R 300s*13 >22.6 The magnitude is calibrated using Pan-STARRS field stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/44373. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42494] GRB 260415A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44372 SUBJECT: GRB 260415A: CALET Gamma-Ray Burst Monitor detection DATE: 26/04/21 09:56:37 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260415A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN #44299; Insight-HXMT/HE detection: Ren et al., GCN #44311) at 04:43:58.34 UTC on 15 April 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1460263432/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a double-peaked structure starting at T-1.5 s, peaking at T+30.1 s, and ending at T+41.1 s. The T90 and T50 durations measured with the SGM data are 36.2 +/- 1.5 s and 19.9 +/- 1.9 s (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1460263432/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44372. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42493] GRB 260415B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44371 SUBJECT: GRB 260415B: CALET Gamma-Ray Burst Monitor detection DATE: 26/04/21 09:51:16 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260415B (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN #44300; NuSTAR detection: Waratkar et al., GCN #44302; Glowbug gamma-ray detection: Woolf et al., GCN #44313) at 02:28:55.55 UTC on 15 April 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1460255329/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T-2.9 s, peaking at T+22.1 s, and ending at T+124.5 s. The T90 and T50 durations measured with the SGM data are 111.6 +/- 1.8 s and 50.7 +/- 1.0 s (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1460255329/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44371. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42492] Fermi GRB 260421C: Global MASTER-Net observations report
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44370 SUBJECT: Fermi GRB 260421C: Global MASTER-Net observations report DATE: 26/04/21 09:30:49 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-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) started inspect of the Fermi GRB 260421C ( Fermi GBM team, GCN 44369) errorbox 165 sec after notice time and 186 sec after trigger time at 2026-04-21 08:28:26 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 51 deg. The sun altitude is -43.9 deg. The galactic latitude b = 19 deg., longitude l = 96 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3263342 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 217 | 2026-04-21 08:28:26 | MASTER-OAGH | (19h 25m 37.26s , +63d 45m 12.4s) | C | 60 | 19.6 | 217 | 2026-04-21 08:28:26 | MASTER-OAGH | (19h 28m 03.53s , +63d 11m 30.5s) | C | 60 | 19.8 | 290 | 2026-04-21 08:29:39 | MASTER-OAGH | (19h 43m 37.39s , +63d 44m 07.3s) | C | 60 | 19.6 | 290 | 2026-04-21 08:29:39 | MASTER-OAGH | (19h 46m 02.78s , +63d 10m 22.7s) | C | 60 | 19.9 | 518 | 2026-04-21 08:33:28 | MASTER-OAGH | (19h 26m 38.22s , +59d 56m 08.4s) | C | 60 | 20.0 | 518 | 2026-04-21 08:33:28 | MASTER-OAGH | (19h 28m 49.30s , +59d 22m 23.7s) | C | 60 | 20.2 | 736 | 2026-04-21 08:36:35 | MASTER-OAGH | (19h 39m 52.48s , +63d 57m 57.9s) | C | 120 | 19.9 | 856 | 2026-04-21 08:36:35 | MASTER-OAGH | (19h 39m 52.48s , +63d 57m 57.9s) | C | 360 | 20.5 | Coadd 736 | 2026-04-21 08:36:35 | MASTER-OAGH | (19h 42m 20.57s , +63d 24m 11.2s) | C | 120 | 20.1 | 856 | 2026-04-21 08:36:35 | MASTER-OAGH | (19h 42m 20.57s , +63d 24m 11.2s) | C | 360 | 20.5 | Coadd 936 | 2026-04-21 08:39:55 | MASTER-OAGH | (19h 39m 52.89s , +63d 57m 53.5s) | C | 120 | 19.9 | 936 | 2026-04-21 08:39:55 | MASTER-OAGH | (19h 42m 21.02s , +63d 24m 06.6s) | C | 120 | 20.1 | 1066 | 2026-04-21 08:42:05 | MASTER-OAGH | (19h 39m 58.99s , +63d 56m 50.1s) | C | 120 | 20.0 | 1066 | 2026-04-21 08:42:05 | MASTER-OAGH | (19h 42m 27.17s , +63d 23m 03.5s) | C | 120 | 20.2 | 1197 | 2026-04-21 08:44:16 | MASTER-OAGH | (19h 39m 53.32s , +63d 57m 47.2s) | C | 120 | 20.0 | 1197 | 2026-04-21 08:44:16 | MASTER-OAGH | (19h 42m 21.81s , +63d 24m 00.3s) | C | 120 | 20.2 | 1328 | 2026-04-21 08:46:27 | MASTER-OAGH | (19h 39m 59.23s , +63d 56m 43.3s) | C | 120 | 19.9 | 1328 | 2026-04-21 08:46:27 | MASTER-OAGH | (19h 42m 27.64s , +63d 22m 56.8s) | C | 120 | 20.2 | 2193 | 2026-04-21 09:01:22 | MASTER-OAGH | (19h 26m 48.80s , +59d 56m 20.2s) | C | 60 | 19.9 | 2193 | 2026-04-21 09:01:22 | MASTER-OAGH | (19h 29m 01.44s , +59d 22m 30.8s) | C | 60 | 20.0 | 2326 | 2026-04-21 09:03:35 | MASTER-OAGH | (19h 17m 11.76s , +61d 50m 25.1s) | C | 60 | 19.7 | 2326 | 2026-04-21 09:03:35 | MASTER-OAGH | (19h 19m 32.38s , +61d 16m 36.3s) | C | 60 | 19.9 | 2397 | 2026-04-21 09:04:46 | MASTER-OAGH | (19h 34m 03.19s , +61d 49m 16.1s) | C | 60 | 19.5 | 2397 | 2026-04-21 09:04:46 | MASTER-OAGH | (19h 36m 23.31s , +61d 15m 26.3s) | C | 60 | 19.9 | 2557 | 2026-04-21 09:06:57 | MASTER-OAGH | (19h 51m 54.15s , +63d 51m 04.9s) | C | 120 | 19.9 | 2557 | 2026-04-21 09:06:57 | MASTER-OAGH | (19h 54m 23.17s , +63d 17m 13.8s) | C | 120 | 20.0 | 2688 | 2026-04-21 09:09:07 | MASTER-OAGH | (19h 52m 00.00s , +63d 50m 02.0s) | C | 120 | 19.9 | 2688 | 2026-04-21 09:09:07 | MASTER-OAGH | (19h 54m 29.04s , +63d 16m 12.0s) | C | 120 | 19.9 | 2819 | 2026-04-21 09:11:18 | MASTER-OAGH | (19h 50m 19.75s , +64d 50m 59.2s) | C | 120 | 19.6 | 2819 | 2026-04-21 09:11:18 | MASTER-OAGH | (19h 52m 54.24s , +64d 17m 09.7s) | C | 120 | 19.6 | 2950 | 2026-04-21 09:13:29 | MASTER-OAGH | (19h 50m 26.43s , +64d 49m 56.1s) | C | 120 | 19.8 | 2950 | 2026-04-21 09:13:29 | MASTER-OAGH | (19h 53m 00.91s , +64d 16m 07.5s) | C | 120 | 19.8 | 3125 | 2026-04-21 09:16:54 | MASTER-OAGH | (19h 26m 53.60s , +59d 55m 26.9s) | C | 60 | 19.4 | 3125 | 2026-04-21 09:16:54 | MASTER-OAGH | (19h 29m 07.76s , +59d 21m 41.7s) | C | 60 | 19.4 | 3197 | 2026-04-21 09:18:06 | MASTER-OAGH | (19h 17m 13.13s , +61d 50m 46.4s) | C | 60 | 19.4 | 3197 | 2026-04-21 09:18:06 | MASTER-OAGH | (19h 19m 35.44s , +61d 17m 01.7s) | C | 60 | 19.5 | 3305 | 2026-04-21 09:19:24 | MASTER-OAGH | (19h 36m 06.37s , +65d 49m 10.5s) | C | 120 | 19.7 | 3305 | 2026-04-21 09:19:24 | MASTER-OAGH | (19h 38m 48.49s , +65d 15m 24.8s) | C | 120 | 19.8 | 3436 | 2026-04-21 09:21:35 | MASTER-OAGH | (19h 36m 10.81s , +65d 50m 43.9s) | C | 120 | 19.3 | 3436 | 2026-04-21 09:21:35 | MASTER-OAGH | (19h 38m 53.00s , +65d 16m 58.7s) | C | 120 | 19.5 | 3567 | 2026-04-21 09:23:46 | MASTER-OAGH | (19h 24m 08.88s , +65d 49m 56.4s) | C | 120 | 19.5 | 3567 | 2026-04-21 09:23:46 | MASTER-OAGH | (19h 26m 51.43s , +65d 16m 11.7s) | C | 120 | 19.5 | 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/44370. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42491] GRB 260421C: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Apr '26

21 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44369 SUBJECT: GRB 260421C: Fermi GBM Final Real-time Localization DATE: 26/04/21 08:35:58 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 08:25:19 UT on 21 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260421C (trigger 798452724.59066 / 260421351). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 295.0, Dec = 64.2 (J2000 degrees, equivalent to J2000 19h 40m, 64d 12'), with a statistical uncertainty of 3.1 degrees. The angle from the Fermi LAT boresight is 59.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421351/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421351/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260421351/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44369. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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