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

[vsnet-grb-info 42790] GRB 260509A: CrAO ZTSh optical upper limit
by GCN Circulars 18 May '26

18 May '26

TITLE: GCN CIRCULAR NUMBER: 44662 SUBJECT: GRB 260509A: CrAO ZTSh optical upper limit DATE: 26/05/18 13:49:55 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), A. Pozanenko (IKI), V. Rumyantsev (CrAO), N. Pankov (IKI), A. Volnova (IKI) report on behalf of IKI GRB-FuN. We observed the field of the GRB 260509A (Götz et al., GCN 44504) with the Shajn 2.6-meter telescope (ZTSh) of the Crimean Astrophysical Observatory (CrAO). We obtained 40*120 s exposures R filter on 2026-05-15 19:45:59--21:09:48 UT (5.94218 days after trigger). We did not detect the OT (O'Neill et al., GCN 44505; Saccardi et al., GCN 44506; Wu et al., GCN 44507; Sánchez Álvarez et al., GCN 44509; Zheng et al., GCN 44510; Kechin et al., GCN 44512; Belkin, GCN 44513; Corcoran et al., GCN 44514; Bochenek and Perley, GCN 44516; Moskvitin and Spiridonova, GCN 44563; Mo et al., GCN 44590; Li et al., GCN 44598) down to the 3-sigma limiting magnitude of R_lim = 24.2. This preliminary photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44662. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42789] GRB 260516D: EP-FXT follow-up observation
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44661 SUBJECT: GRB 260516D: EP-FXT follow-up observation DATE: 26/05/17 10:45:05 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), Z.M. Wang (BNU), W.F. Wen (SZTU), Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed an automatic follow-up observation of GRB 260516D detected by SVOM/ECLAIRs (SVOM/sb26051616, Brunet et al., GCN 44649). The follow-up obervation started at 2026-05-16 22:46:58 UTC, approximately 2.1 hours after the SVOM trigger, with a total exposure time of 6080 s. On-ground analysis of the FXT data found an uncatalogued fading source within the ECLAIRs error circle at R.A., Dec. = 233.8275, 6.5288 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). This position is consistent with the optical counterpart (Li et al., GCN 44654, Mohan et al., GCN 44655, Izzo et al., GCN 44656, García et al., GCN 44657, Wu et al., GCN 44659, Belkin et al., GCN 44660). The average FXT 0.3-10 keV spectrum can be fitted with an absorbed power-law model, with the Galactic hydrogen column density fixed at 4.71 x 10^20 cm^-2, an intrinsic hydrogen column density of 6.29 (-1.71/+1.71) x 10^21 cm^-2, and a photon index of 2.43 (-0.08/+0.08). The derived unabsorbed average flux in the 0.3-10 keV band is 3.99 (-0.14/+0.15) x 10^(-12) erg/s/cm^2. 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/44661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42788] GRB 260516D: GOTO optical counterpart detection
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44660 SUBJECT: GRB 260516D: GOTO optical counterpart detection DATE: 26/05/17 08:55:51 GMT FROM: Sergey Belkin at Monash University <sergey.belkin(a)monash.edu> S. Belkin, B. P. Gompertz, M. Wortley, G. Ramsay, D. O'Neill, R. Starling, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, M. Pursiainen, on behalf of GOTO collaboration We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM/ECLAIRs detection of the possible short faint burst GRB 260516D (Brunet et al., GCN 44649). Observations of the field were obtained with GOTO-N on 2026-05-16 and 2026-05-17 UT in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline (Lyman et al. 2026). Difference imaging was performed using deeper template observations of the same pointings. We detect the optical afterglow candidate reported by SVOM/VT (Li et al., GCN 44654), the GROWTH-India Telescope (Mohan et al., GCN 44655), GTC/OSIRIS+ (Izzo et al., GCN 44656), SVOM/COLIBRÍ (García García et al., GCN 44657), and LCO (Wu et al., GCN 44659). The source was initially detected with L = 19.29 +/- 0.05 AB mag at 2026-05-16 22:03:56 UT (T0 +1.40 hr), before fading to L = 21.01 +/- 0.34 AB mag at 2026-05-17 01:26:52 UT (T0 +4.78 hr). These two detections imply a preliminary temporal decay index of alpha_L = 1.30 +/- 0.26, consistent with the optical decay reported by García García et al. (GCN 44657). GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham, and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44660. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42787] GRB 260516D: LCO optical observations
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44659 SUBJECT: GRB 260516D: LCO optical observations DATE: 26/05/17 08:22:30 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), A. Saccardi (CEA/Irfu), L.P. Xin (NAOC) report on behalf of the SVOM mission team: We observed the field of the SVOM/ECLAIRs GRB 260516D (Brunet et al., GCN 44649) with the LCO 1m telescope at McDonald Observatory and Cerro Tololo equipped with the Sinistro instrument. Our observation started on 2026-05-17 at 06:26:56 UT (about 9.79 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters. The optical counterpart (Li et al., GCN 44654; Mohan et al., GCN 44655; García et al., GCN 44657) with redshift of 1.801 (Izzo et al., GCN 44656) is faintly detected in our images. We measure the following magnitudes calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: r = 21.75 +/- 0.10 AB (mid-time 9.88 hr after the trigger); z > 21.2 AB (3-sigma, mid-time 10.00 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/44659. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42786] GRB 260515A: further Liverpool Telescope observations
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44658 SUBJECT: GRB 260515A: further Liverpool Telescope observations DATE: 26/05/17 08:10:40 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of GRB 260515A (Brunetet al., GCN 44622) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x110s exposures in SDSS r and i filters, starting at 2026-05-12 00:42:25 UT, approximately 5.55 hours after trigger. We detect a source in the stacked images in both filters at the position reported by He et al. (GCN 44623), and observed also by Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Wu et al., GCN 44628, Dennefeld et al., GCN 44633; Li et al., GCN 44634, Antier et al., GCN 44643; Dimple et al. GCN 44646; and Moskvitin et al., GCN 44652: MJD (mid) T_mid-T_0 Filter Mag. (AB) 61176.03308 5.64 h r 21.32 ± 0.06 61176.04059 5.82 h i 21.26 ± 0.07 The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42785] GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44657 SUBJECT: GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 26/05/17 06:24:29 GMT FROM: Leonardo Enrique García García <lgarcia(a)astro.unam.mx> Leonardo García García (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM) and Andrea Saccardi (CEA) report: We imaged the field of the SVOM/ECLAIRs GRB 260516D (M. Brunet et al., GCN Circ. 44649) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-17 04:04 to 05:51 UTC (from to 7.48 to 9.25 hours after the trigger) and obtained 15 minutes of exposure in the r filter and 44 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 PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the source reported by Li et al. (GCN Circ. 44654) and de Ugarte Postigo et al. (GCN Circ. 44656) with preliminary unsubtracted magnitudes of: r = 21.65 +/- 0.07, z = 21.66 +/- 0.16. Using the combined r’ and r- band photometry from GCNs 44655 and 44656 together with our COLIBRI observations, we estimate the optical afterglow temporal decay index to be approximately alpha ≈ 1.4. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/44657. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42784] GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44656 SUBJECT: GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801 DATE: 26/05/17 04:17:13 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> L. Izzo (INAF/OACN and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), A. de Ugarte Postigo (LAM), S. Geier (GTC), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), F. Perez Toledo (GTC) report: We observed the optical counterpart (Li et al., GCN 44654; Mohan et al., GCN 44655) of GRB 260516D (Brunet et al., GCN 44649) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In the 30-s acquisition image (beginning on 2026-05-17 at 02:54:51, that is 6.25 hr after trigger), the optical afterglow is well detected with a magnitude 21.0 ± 0.1 (AB), calibrated against nearby Pan-STARRS objects, and not corrected for Galactic extinction. A total of 3 spectra of 900 s were secured, starting at 03:06:24.010 UT (6.44 hr after trigger), using grism R1000B. Continuum is visible over the range 3650-7800 AA. A number of metal absorption features are detected, which we interpret as due to, among others, C II, C IV, Si II, Fe II, Al II, and Al III, all at a common redshift z = 1.801, which we suggest to be the redshift of GRB 260516D. This work has used the GRBspec database at http://grbspec.eu (de Ugarte Postigo et al. 2014, doi:10.1117/12.2055774). View this GCN Circular online at https://gcn.nasa.gov/circulars/44656. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42783] GRB 260516D: GROWTH-India Telescope optical counterpart discovery
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44655 SUBJECT: GRB 260516D: GROWTH-India Telescope optical counterpart discovery DATE: 26/05/17 01:33:09 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan (IITB), V. Swain (IITB), A.P. Saikia (IITB), S. Patil (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team: We observed the field of GRB 260515D (Brunet et al., GCN 44649), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-05-16 22:19:57 (UTC), i.e., 1.67 hours after the trigger, and obtained multiple exposures in the r' filter. The observations were carried out at relatively high airmass (~2). We report the discovery of the possible counterpart whose coordinates are RA, Dec = 233.827989 (deg), 6.529308 (deg). No known minor planet was found at the source position during the time of observation. The photometric results are as follows: | MJD (mid) | Filter | tmid-t0 (minutes) | Exposure Time (sec) | Magnitude (AB) | | ------------ | ------ | ----------------- | ------------------- | -------------- | | 61176.93225 | r' | 102.62 | 1x300 | 19.17 +- 0.10 | | 61176.94497 | r' | 120.93 | 1x420 | 19.45 +- 0.09 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our results are consistent with other optical observations (Jelinek et al., GCN 44653) The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/44655. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42782] GRB 260516D: SVOM/VT optical bright candidate
by GCN Circulars 17 May '26

17 May '26

TITLE: GCN CIRCULAR NUMBER: 44654 SUBJECT: GRB 260516D: SVOM/VT optical bright candidate DATE: 26/05/17 01:27:37 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, 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 and A. Saccardi (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the field of possible short burst GRB 260516D detected by SVOM/ECLAIRs (Brunet et al., GCN 44619). The observation started at 2026-05-16T22:20:51 UTC, 1.69 hour post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued optical source was clearly detected in single frames of both channels within the errobox of SVOM/ECLAIRs, compared to the Legacy Survey. The position is at R.A., Dec. = 233.827956, 6.529103 degrees, equivalent to: R.A. (J2000) = 15:35:18.71 Dec. (J2000) = +6:31:44.77 with an uncertainty of 0.5 arcsec. The measurements in AB magnitudes are given below: Mid_time Band Exposure Time Magnitude (AB) 1.71 hour VT_B 70 sec 19.62 +/- 0.05 mag 1.69 hour VT_R 70 sec 19.00 +/- 0.05 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/44654. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42781] GRB 260516D: FRAM-ORM optical limit
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44653 SUBJECT: GRB 260516D: FRAM-ORM optical limit DATE: 26/05/16 23:59:09 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> Martin Jelinek, Filip Novotny and Jan Strobl (ASU CAS Ondrejov, CZ), Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ) report: The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically to the SVOM/ECLAIRs alert of GRB 260516D (Brunet et al., GCNC 44649), obtaining a series of unfiltered 60s images starting at 20:54:16 UT, i.e. ~948s post trigger. We do not detect any new or strongly variable source in comparison to the ATLAS REFCAT2 catalog. In single images the detection limit gradually improved from R_C > 17.1 in the first frame (midtime ~978s post trigger), stabilizing at R_C > ~18.3–18.4 around ~2000s post trigger and remaining there for the rest of the ~one hour sequence. Combining images in groups of 10 (10x60s), we reach limits of R_C > ~20 (R_C > ~19.3 for the first combined frame). View this GCN Circular online at https://gcn.nasa.gov/circulars/44653. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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