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

[vsnet-grb-info 42010] GRB 260228A: CAHA 2.2m telescope optical upper limit
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43893 SUBJECT: GRB 260228A: CAHA 2.2m telescope optical upper limit DATE: 26/03/01 22:42:20 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S. Guziy (IAA-CSIC), Y.-D. Hu (GXU), M.D. Caballero-García, M. Gritsevich, I. Pérez-García, R. Sánchez-Ramírez, S-Y. Wu (IAA-CSIC), G. García-Segura (UNAM), M. Blazek, I. Vico (CAHA) and A.J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration, report: Following the detection of GRB 260228A by SVOM/ECLAIRs (Julakanti et al., GCNC 43882), we triggered the 2.2 m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almería, Spain). Images were obtained starting on Mar. 1 at 03:34 UT (i.e., ~6.7 hours after the trigger) in the Sloan griz bands covering the entire error region. In the co-added images (60 × 6 s), no optical transient is detected down to limiting magnitudes of 22.1 mag (r') and 21.0 (i'). This non-detection is consistent with the reports from SVOM/VT (Li et al., GCNC 43886) and SVOM/COLIBRÍ (Mandarakas et al. GCNC 43892). We thank the staff at Calar Alto Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42009] GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43892 SUBJECT: GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 26/03/01 17:32:00 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Margarita Pereyra (UNAM), Nathaniel R. Butler (ASU), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Yashaswi Julakanti, Rob Eyles-Ferris report: We imaged the field of the SVOM GRB 260228A (Julakanti et al., GCN Circ. 43882) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-01 07:28 to 11:52 UTC (from 10.55 to 14.96 hours after the trigger) and obtained 120 minutes of exposure in the r filter and 129 minutes of exposure in the z filter. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. 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. In the stacked image, comparing to Pan-STARRS and Legacy Survey (Dey et al. 2019) images, we do not detect any new source within the ECLAIRs uncertainty region (Julakanti et al., GCN Circ. 43882) down to the following 5-sigma limits: r > 23.3 z > 22.5 This upper limit is consistent with the one reported by Li et al. (GCN Circ. 43886). 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/43892. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42008] EP260227a: Mephisto optical detection
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43891 SUBJECT: EP260227a: Mephisto optical detection DATE: 26/03/01 14:58:50 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Shiyan Zhong, Hongguang Li, Qinhao Shao, Yuan Fang, Jian Cui, Guowang Du, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Jianghua Zhang, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP260227a (Wang et al., GCN 43869) was observed with the 1.6-meter Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. The simultaneous observations in Mephisto u/g/i bands were started from 2026-02-27T20:20:38 (~8 minutes after the trigger). The field was again simultaneously observed in v/r/z bands (starting from 2026-02-27T20:23:47). We detected a source at the position reported by Eyles-Ferris et. al. (GCN 43867) and other groups Li et al., (GCN 43868); Fu et al, (GCN 43873); Mandarakas et al., (GCN 43874); Eyles-Ferris and Tanvir et al., (GCN 43875); Malesani et al., (GCN 43876); Eyles-Ferris et al., (GCN 43877); Strausbaugh et al., (GCN 43879); Bochenek et al., (GCN 43880); Gassert et al., (GCN 43881); Gupta et al., (GCN 43884); Ma et al., (GCN 43887) and Eyles-Ferris et al., (GCN 43888). The preliminary photometry results (without extinction correction) are listed below: Start_Time (UT) | Band | Exp(s) | Mag/LimMag(AB) --------------------|------|--------|-------------------- 2026-02-27T20:20:38 | u | 45 | >20.86 (3-sigma) 2026-02-27T20:20:38 | g | 45 | 20.58 +/- 0.32 2026-02-27T20:20:38 | i | 45 | 19.92 +/- 0.18 --------------------|------|--------|-------------------- 2026-02-27T20:23:47 | v | 45 | >20.80 (3-sigma) 2026-02-27T20:23:47 | r | 45 | 20.13 +/- 0.25 2026-02-27T20:23:47 | z | 45 | >20.28 (3-sigma) ------------------------------------------------------------------------------------------------- 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. 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 these are currently in the commissioning phase. 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/43891. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42007] GRID detection of GRB 260225D
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43890 SUBJECT: GRID detection of GRB 260225D DATE: 26/03/01 13:20:06 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Longhao Li, Chenyu Wang, Zirui Yang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 260225D, which was also observed by Glowbug (GCN #43856) and SVOM/GRM(GCN #43885). The event triggered GRID at T0 = 2026-02-25 19:51:28.7 UTC and was detected by both GRID-09B and GRID-11B, with a weaker signal observed by GRID-11B. Temporal analysis based on GRID-09B data yields a burst duration of T90 = 1.96 ± 0.08 s in the 30–2000 keV energy range. At present, only the GRID light curve is available. No spectral analysis is reported at this stage. The GRID light curve of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260225D/GRID_260… 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: 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/43890. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42006] EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43889 SUBJECT: EP-WXT trigger 01709258652: 50cm Telescope multi-band observations DATE: 26/03/01 13:18:28 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Yuan Fang, Hong Guang Li, Shiyan Zhong, Qinhao Shao, Jian Cui, Yu Pan, Xingzhu Zou, Xinlei Chen, Brajesh Kumar, Guowang Du, Jinghua Zhang, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The 50cm Telescope of the Yunnan University was triggered on 2026-02-26T14:42:36 (~52.6 min after the EP/WXT trigger) to observe the field of EP-WXT trigger 01709258652 (Yang et al., GCN 43849; Wu et al., GCN 43857). A sequence of g, r, i and z-band images was obtained about 51 min. The photometry of suggested flare star LP 435-538 (High Proper Motion Star; Yang et al., GCN 43849) shows a decline from 14.41 to 14.89 mag (AB, calibrated against Gaia XP) in g-band over ~47 min. The fading was relatively gradual during this observation period. These results further support the previous finding by Wu et al. (GCN 43857) that EP X-ray trigger was associated with a stellar flare. The 50cm telescope is located at the Lijiang Observatory, China and is part of 50cm array facility. The camera employs an ON Semi KAF-50100 sensor, with 8176 x 6132 pixels of size 6μm (corresponding to 0.3 arcsec projected on the sky). The telescope is utilized for a prompt monitoring of transients and also serves as the supporting facility for monitoring the Mephisto detected targets (Chen et al. 2024, Yang et al. 2024). View this GCN Circular online at https://gcn.nasa.gov/circulars/43889. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42005] EP260227a: further LCO observations
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43888 SUBJECT: EP260227a: further LCO observations DATE: 26/03/01 10:25:41 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), and J. Chacón (PUC) report on behalf of a larger collaboration: We observed the optical counterpart of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with an LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. We obtained nine 300 s exposures in the r band from 2026-03-01 07:52:01 to 2026-03-01 08:43:10 UT (t_mid = 36.09 hr). In our stacked image, we clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al, GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris and Tanvir et al., GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al., GCN 43879; Bochenek et al., GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884; Ma et al., GCN 43887). We measure an AB magnitude of r = 22.82 +/- 0.28 calibrated to Pan-STARRS and not corrected for Galactic extinction. Our observations suggest there is no significant evolution since the observations of Gupta et al. (GCN 43884) ~12 hr earlier. View this GCN Circular online at https://gcn.nasa.gov/circulars/43888. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42004] EP260227a: SVOM/VT optical observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43887 SUBJECT: EP260227a: SVOM/VT optical observation DATE: 26/03/01 09:51:54 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) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260227a detected by EP/WXT (Wang et al., GCN 43869). SVOM/VT began observing the field at 2026-02-28T07:20:51 UTC, 11.14 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh & Cucchiara, GCN 43879; Bochenek & Perley, GCN 43880; Gassert et al., GCN 43881; Gupta et al., GCN 43884) was detected in both VT_B and VT_R bands. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|-------------- 11.362 | 38*50 | VT_B | 21.9+-0.1 11.313 | 31*50 | VT_R | 21.3+-0.1 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/43887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42003] GRB 260228A: SVOM/VT optical upper limits
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43886 SUBJECT: GRB 260228A: SVOM/VT optical upper limits DATE: 26/03/01 08:26:45 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Z. H. Yao, C. Wu, Y. N. Ma, 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), A. Li (BNU), Z. M. Wang (BNU), Y. Julakanti (Univ. Leicester) and R. Eyles-Ferris (Univ. Leicester) report on behalf of the SVOM/VT team. SVOM/VT performed an observation with automatic slew to the field of GRB 260228A triggered by SVOM/ECLAIRs (sb26022802, Julakanti et al., GCN 43882). The observation started at 2026-02-28T21:50:40 UTC, i.e., about 55 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No uncatalogued sources were detected within the ECLAIRs error box (Julakanti et al., GCN 43882), compared to the Legacy Survey catalog. The 3 sigma upper limits are derived as follows: Mid time | Band | Exposure Time | 3 sigma upper limit 1.155 hour VT_B 35*50 sec > 23.3 mag 1.169 hour VT_R 34*50 sec > 23.0 mag More detailed analysis is still ongoing. 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/43886. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42002] GRB 260225D: SVOM/GRM observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43885 SUBJECT: GRB 260225D: SVOM/GRM observation DATE: 26/03/01 08:05:24 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260225D (SVOM trigger reference: sb26022503) at 2026-02-25T19:51:30.000 (T0), which is also detected by Konus-Wind (Trig_Time 19:51:32.84), Glowbug (C.C. Cheung et al., GCN #43856) and GRID. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two pulses with a T90 of 2.0 +1.0/-0.6 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260225D.png In addition, the position of this burst, according to Glowbug localization (RA = 94.7, Dec = 13.8, C.C. Cheung et al., GCN #43856), is located at about 93 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Nevertheless, ECLAIRs detected the GRB through the shield above 50 keV. With this localization, the time-averaged spectrum from T0-2.0 to T0+4.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.12 +0.18/-0.15 and the cutoff energy, parameterized as Epeak, is 700 +480/-250 keV. The event fluence (10-1000 keV) in this time interval is (8.5 +0.8/-0.9)E-07 erg/cm^2. The localization of GRB 260225D in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225D_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42001] EP260227A: 3.6m DOT optical afterglow detection
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43884 SUBJECT: EP260227A: 3.6m DOT optical afterglow detection DATE: 26/03/01 07:52:34 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina Kar, and Kuntal Misra (ARIES) report: We observed the field of EP260227A detected by Einstein Probe WXT (Wang et al., GCN 43869) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-02-28 at 21:17:26 UT, i.e., ~25.08 hours after the EP/WXT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect an optical counterpart in our stacked image at the position given by the Eyles-Ferris et al. (GCN 43867). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hours) Filter Exp time (s) Magnitude ================================================================== 2026-02-28 21:17:26 ~25.08 R 300s*24 22.92 +/-0.06 Our detection is consistent with Eyles-Ferris et al. (GCN 43867); Li et al. (GCN 43868); Lipunov et al. (GCN 43870); Fu et al.(GCN 43873); Mandarakas et al. (GCN 43874); Eyles-Ferris and N. R. Tanvir et al. (GCN 43875); Malesani et al. (GCN 43876); Eyles-Ferris et al. (GCN 43877); Strausbaugh et al. (GCN 43879); Bochenek et al. (GCN 43880); Gassert et al. (GCN 43881). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/43884. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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