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[vsnet-grb-info 42760] EP260514a: COLIBRÍ optical upper limits
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44632 SUBJECT: EP260514a: COLIBRÍ optical upper limits DATE: 26/05/16 03:23:14 GMT FROM: freddalvarez(a)astro.unam.mx Fredd Sánchez Álvarez (UNAM), Noémie Globus (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), 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), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (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), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260514a detected by Einstein Probe/WXT (Cheng et al., GCN Circ. 44613 ) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-15 03:27 to 03:44 UTC, corresponding to 10.52 to 10.80 hours after the trigger, and obtained 14 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked images and after performing image subtraction using templates from the DESI Legacy Survey (Dey et al. 2019), we do not detect any new sources within the WXT error region (Cheng et al., GCN Circ. 44613) down to the following 5-sigma limits: r > 22.1. z > 20.9. Our upper limits are consistent with the previously reported by MASTER (Lipunov et al., GCN Circ. 44614) and GROWTH-India Telescope (Mohan et al., GCN Circ. 44619). We note the presence of four quasars: SDSS J141722.46+492142.1 SDSS J141658.83+492220.9 SDSS J141720.92+492351.5 SDSS J141653.45+492109.8 within the WXT region and, considering our upper limits, we cannot rule out the possibility that the trigger is related to one of these sources. 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/44632. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42759] GRB 260516A: Fermi GBM Final Real-time Localization
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44631 SUBJECT: GRB 260516A: Fermi GBM Final Real-time Localization DATE: 26/05/16 03:01:20 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 02:50:48 UT on 16 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260516A (trigger 800592653.936132 / 260516119). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 111.5, Dec = -37.6 (J2000 degrees, equivalent to J2000 07h 26m, -37d 36'), with a statistical uncertainty of 7.7 degrees. The angle from the Fermi LAT boresight is 163.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516119/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516119/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516119/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44631. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42758] GRID detection of GRB 260507A
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44630 SUBJECT: GRID detection of GRB 260507A DATE: 26/05/16 01:47:43 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Longhao Li, Tingkai Sun, Chenyv Wang report on behalf of the GRID Collaboration: GRID-09 reports the detection of the long-duration GRB 260507A, which was also detected by Fermi GBM (GCN Circular 44493). The event was triggered with GRID on 2026-05-07 at 20:28:00 UTC. The measured burst duration (T90) in the 30-2000 keV range is approximately 12.102083333333333 +/- 2.8242414050797913 seconds. The GRID light curve of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260507A/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 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/44630. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42757] GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44629 SUBJECT: GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764 DATE: 26/05/16 01:11:21 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), S. Geier (GTC), A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), L. Izzo (INAF/OACN and DARK/NBI), 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 (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Wu et al., GCN 44628) of GRB 260515A (Brunet et al., GCN 44622) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument. In the 20-s acquisition image (beginning on 2026-05-15 at 23:48:49.010 UT, that is 4.67 hr after trigger), the optical afterglow is well detected with a magnitude r = 21.15 ± 0.10 (AB), calibrated against nearby Pan-STARRS objects, and not corrected for Galactic extinction. A total of 3 spectra of 1200 s were secured, starting on 2026-05-15 at 23:52:26.010 UT (4.73 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 Fe II, Mg II, and Mg I, all at a common redshift z = 0.764, which we suggest to be the redshift of GRB 260515A. We also detect emission due to the [O II] doublet at the same redshift. 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/44629. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42756] GRB 260515A: LCO optical observations
by GCN Circulars 16 May '26

16 May '26

TITLE: GCN CIRCULAR NUMBER: 44628 SUBJECT: GRB 260515A: LCO optical observations DATE: 26/05/16 00:11:51 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), report on behalf of the SVOM mission team: We observed the field of the SVOM/ECLAIRs GRB 260515A (Brunet et al., GCN 44622) with the LCO 1m telescope at Teide Observatory equipped with the Sinistro instrument. Our observation started on 2026-05-15 at 22:42:33 UT (about 3.57 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 (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626) is faintly detected in our images. We measure the following magnitudes calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r = 21.22 +/- 0.09 AB (mid-time 4.44 hr after the trigger); z > 20.5 AB (3-sigma, mid-time 3.63 hr after the trigger). A marginal detection is recovered through forced photometry in the z band as well, to the level of z = 20.6 +/- 0.4 AB. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/44628. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42755] SVOM GRB 260515A: Global MASTER-Net observations report
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44627 SUBJECT: SVOM GRB 260515A: Global MASTER-Net observations report DATE: 26/05/15 21:53:05 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-Tavrida robotic telescope [1] located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the SVOM GRB 260515A ( SVOM/ECLAIRs Commissioning Team et al., GCN 44622) errorbox 30 sec after notice time and 659 sec after trigger time at 2026-05-15 19:19:18 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 32 deg. The sun altitude is -18.8 deg. The galactic latitude b = 58 deg., longitude l = 36 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3316887 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 719 | 2026-05-15 19:19:18 | MASTER-Tavrida | (15h 10m 30.15s , +24d 42m 28.1s) | C | 120 | 18.8 | 842 | 2026-05-15 19:21:20 | MASTER-Tavrida | (15h 10m 30.34s , +24d 42m 18.6s) | C | 120 | 19.1 | 965 | 2026-05-15 19:23:23 | MASTER-Tavrida | (15h 10m 30.45s , +24d 42m 11.4s) | C | 120 | 19.1 | 1087 | 2026-05-15 19:25:26 | MASTER-Tavrida | (15h 10m 30.55s , +24d 42m 04.2s) | C | 120 | 18.9 | 1210 | 2026-05-15 19:27:28 | MASTER-Tavrida | (15h 10m 30.61s , +24d 41m 58.5s) | C | 120 | 19.4 | 1332 | 2026-05-15 19:29:31 | MASTER-Tavrida | (15h 10m 30.65s , +24d 41m 52.9s) | C | 120 | 19.4 | 1455 | 2026-05-15 19:31:33 | MASTER-Tavrida | (15h 10m 30.66s , +24d 41m 47.7s) | C | 120 | 19.5 | 1577 | 2026-05-15 19:33:36 | MASTER-Tavrida | (15h 10m 30.65s , +24d 41m 42.7s) | C | 120 | 19.5 | 1700 | 2026-05-15 19:35:38 | MASTER-Tavrida | (15h 10m 30.62s , +24d 41m 38.1s) | C | 120 | 19.6 | 1822 | 2026-05-15 19:37:41 | MASTER-Tavrida | (15h 10m 30.62s , +24d 41m 33.2s) | C | 120 | 19.6 | 1945 | 2026-05-15 19:39:44 | MASTER-Tavrida | (15h 10m 30.62s , +24d 41m 28.5s) | C | 120 | 19.6 | 2068 | 2026-05-15 19:41:46 | MASTER-Tavrida | (15h 10m 30.61s , +24d 41m 24.0s) | C | 120 | 19.6 | 2190 | 2026-05-15 19:43:49 | MASTER-Tavrida | (15h 10m 30.62s , +24d 41m 19.0s) | C | 120 | 19.6 | 2313 | 2026-05-15 19:45:52 | MASTER-Tavrida | (15h 10m 30.63s , +24d 41m 14.6s) | C | 120 | 19.5 | 2436 | 2026-05-15 19:47:54 | MASTER-Tavrida | (15h 10m 30.61s , +24d 41m 09.9s) | C | 120 | 19.6 | 2558 | 2026-05-15 19:49:57 | MASTER-Tavrida | (15h 10m 30.58s , +24d 41m 05.5s) | C | 120 | 19.6 | 2681 | 2026-05-15 19:51:59 | MASTER-Tavrida | (15h 10m 30.55s , +24d 41m 00.9s) | C | 120 | 19.6 | 2804 | 2026-05-15 19:54:02 | MASTER-Tavrida | (15h 10m 30.53s , +24d 40m 56.5s) | C | 120 | 19.7 | 2926 | 2026-05-15 19:56:05 | MASTER-Tavrida | (15h 10m 30.51s , +24d 40m 52.0s) | C | 120 | 19.6 | 3049 | 2026-05-15 19:58:07 | MASTER-Tavrida | (15h 10m 30.50s , +24d 40m 47.5s) | C | 120 | 19.7 | 3179 | 2026-05-15 20:00:18 | MASTER-Tavrida | (15h 10m 34.07s , +24d 41m 17.5s) | C | 120 | 19.7 | 3302 | 2026-05-15 20:02:20 | MASTER-Tavrida | (15h 10m 34.06s , +24d 41m 13.1s) | C | 120 | 19.7 | 3424 | 2026-05-15 20:04:23 | MASTER-Tavrida | (15h 10m 34.06s , +24d 41m 08.9s) | C | 120 | 19.7 | 3547 | 2026-05-15 20:06:26 | MASTER-Tavrida | (15h 10m 34.02s , +24d 41m 04.4s) | C | 120 | 19.7 | 3670 | 2026-05-15 20:08:28 | MASTER-Tavrida | (15h 10m 34.02s , +24d 41m 00.1s) | C | 120 | 19.7 | 3793 | 2026-05-15 20:10:31 | MASTER-Tavrida | (15h 10m 34.02s , +24d 40m 55.8s) | C | 120 | 19.7 | 3915 | 2026-05-15 20:12:34 | MASTER-Tavrida | (15h 10m 34.02s , +24d 40m 51.4s) | C | 120 | 19.7 | 4038 | 2026-05-15 20:14:36 | MASTER-Tavrida | (15h 10m 34.01s , +24d 40m 47.0s) | C | 120 | 19.7 | 4161 | 2026-05-15 20:16:39 | MASTER-Tavrida | (15h 10m 34.00s , +24d 40m 42.8s) | C | 120 | 19.6 | 4283 | 2026-05-15 20:18:42 | MASTER-Tavrida | (15h 10m 34.02s , +24d 40m 38.5s) | C | 120 | 19.8 | 4406 | 2026-05-15 20:20:44 | MASTER-Tavrida | (15h 10m 34.01s , +24d 40m 34.2s) | C | 120 | 19.9 | 4529 | 2026-05-15 20:22:47 | MASTER-Tavrida | (15h 10m 34.01s , +24d 40m 30.0s) | C | 120 | 19.9 | 4651 | 2026-05-15 20:24:50 | MASTER-Tavrida | (15h 10m 33.97s , +24d 40m 26.2s) | C | 120 | 19.8 | 4774 | 2026-05-15 20:26:53 | MASTER-Tavrida | (15h 10m 33.93s , +24d 40m 22.2s) | C | 120 | 19.8 | 4897 | 2026-05-15 20:28:55 | MASTER-Tavrida | (15h 10m 33.91s , +24d 40m 17.9s) | C | 120 | 19.9 | 5020 | 2026-05-15 20:30:58 | MASTER-Tavrida | (15h 10m 33.93s , +24d 40m 13.4s) | C | 120 | 19.9 | 5143 | 2026-05-15 20:33:01 | MASTER-Tavrida | (15h 10m 33.94s , +24d 40m 09.2s) | C | 120 | 19.9 | 5265 | 2026-05-15 20:35:04 | MASTER-Tavrida | (15h 10m 33.96s , +24d 40m 04.8s) | C | 120 | 19.9 | 5388 | 2026-05-15 20:37:06 | MASTER-Tavrida | (15h 10m 33.97s , +24d 40m 00.6s) | C | 120 | 19.9 | 5510 | 2026-05-15 20:39:09 | MASTER-Tavrida | (15h 10m 33.95s , +24d 39m 56.5s) | C | 120 | 19.9 | 5633 | 2026-05-15 20:41:12 | MASTER-Tavrida | (15h 10m 33.91s , +24d 39m 52.7s) | C | 120 | 19.8 | 5756 | 2026-05-15 20:43:14 | MASTER-Tavrida | (15h 10m 33.93s , +24d 39m 48.3s) | C | 120 | 19.9 | 5878 | 2026-05-15 20:45:17 | MASTER-Tavrida | (15h 10m 33.94s , +24d 39m 43.8s) | C | 120 | 19.9 | 6001 | 2026-05-15 20:47:20 | MASTER-Tavrida | (15h 10m 33.96s , +24d 39m 39.5s) | C | 120 | 19.9 | 6124 | 2026-05-15 20:49:23 | MASTER-Tavrida | (15h 10m 33.99s , +24d 39m 35.1s) | C | 120 | 19.9 | 6246 | 2026-05-15 20:51:25 | MASTER-Tavrida | (15h 10m 33.93s , +24d 39m 31.4s) | C | 120 | 19.7 | 6369 | 2026-05-15 20:53:28 | MASTER-Tavrida | (15h 10m 33.93s , +24d 39m 27.2s) | C | 120 | 19.9 | 6492 | 2026-05-15 20:55:31 | MASTER-Tavrida | (15h 10m 33.95s , +24d 39m 22.9s) | C | 120 | 19.8 | 6615 | 2026-05-15 20:57:33 | MASTER-Tavrida | (15h 10m 34.00s , +24d 39m 18.6s) | C | 120 | 19.9 | 6737 | 2026-05-15 20:59:36 | MASTER-Tavrida | (15h 10m 34.00s , +24d 39m 14.5s) | C | 120 | 19.9 | 6860 | 2026-05-15 21:01:38 | MASTER-Tavrida | (15h 10m 34.02s , +24d 39m 10.3s) | C | 120 | 19.9 | 6983 | 2026-05-15 21:03:41 | MASTER-Tavrida | (15h 10m 34.07s , +24d 39m 06.1s) | C | 120 | 19.8 | 7105 | 2026-05-15 21:05:44 | MASTER-Tavrida | (15h 10m 34.10s , +24d 39m 01.9s) | C | 120 | 19.9 | 7228 | 2026-05-15 21:07:46 | MASTER-Tavrida | (15h 10m 34.10s , +24d 38m 57.7s) | C | 120 | 19.9 | 7350 | 2026-05-15 21:09:49 | MASTER-Tavrida | (15h 10m 34.11s , +24d 38m 53.5s) | C | 120 | 19.7 | 7472 | 2026-05-15 21:11:51 | MASTER-Tavrida | (15h 10m 34.14s , +24d 38m 49.3s) | C | 120 | 19.8 | 7595 | 2026-05-15 21:13:54 | MASTER-Tavrida | (15h 10m 34.17s , +24d 38m 45.0s) | C | 120 | 19.8 | 7718 | 2026-05-15 21:15:56 | MASTER-Tavrida | (15h 10m 34.22s , +24d 38m 40.5s) | C | 120 | 19.8 | 7840 | 2026-05-15 21:17:58 | MASTER-Tavrida | (15h 10m 34.23s , +24d 38m 36.3s) | C | 120 | 19.9 | 7962 | 2026-05-15 21:20:01 | MASTER-Tavrida | (15h 10m 34.25s , +24d 38m 31.9s) | C | 120 | 19.9 | 8085 | 2026-05-15 21:22:03 | MASTER-Tavrida | (15h 10m 34.28s , +24d 38m 27.7s) | C | 120 | 19.8 | 8207 | 2026-05-15 21:24:06 | MASTER-Tavrida | (15h 10m 34.33s , +24d 38m 23.2s) | C | 120 | 19.9 | 8330 | 2026-05-15 21:26:08 | MASTER-Tavrida | (15h 10m 34.34s , +24d 38m 19.1s) | C | 120 | 19.9 | 8452 | 2026-05-15 21:28:11 | MASTER-Tavrida | (15h 10m 34.36s , +24d 38m 14.5s) | C | 120 | 19.9 | 8575 | 2026-05-15 21:30:14 | MASTER-Tavrida | (15h 10m 34.36s , +24d 38m 09.9s) | C | 120 | 19.8 | 8698 | 2026-05-15 21:32:16 | MASTER-Tavrida | (15h 10m 34.41s , +24d 38m 05.3s) | C | 120 | 19.9 | 8820 | 2026-05-15 21:34:19 | MASTER-Tavrida | (15h 10m 34.43s , +24d 38m 00.8s) | C | 120 | 19.9 | 8943 | 2026-05-15 21:36:21 | MASTER-Tavrida | (15h 10m 34.46s , +24d 37m 56.3s) | C | 120 | 19.9 | 9065 | 2026-05-15 21:38:24 | MASTER-Tavrida | (15h 10m 34.51s , +24d 37m 51.7s) | C | 120 | 19.9 | 9188 | 2026-05-15 21:40:27 | MASTER-Tavrida | (15h 10m 34.53s , +24d 37m 47.2s) | C | 120 | 19.8 | 9311 | 2026-05-15 21:42:29 | MASTER-Tavrida | (15h 10m 34.57s , +24d 37m 42.6s) | C | 120 | 19.8 | 9433 | 2026-05-15 21:44:32 | MASTER-Tavrida | (15h 10m 34.59s , +24d 37m 38.0s) | 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/44627. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42754] GRB 260515A: NOT optical observations.
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44626 SUBJECT: GRB 260515A: NOT optical observations. DATE: 26/05/15 21:31:23 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> L. B. He (NAOC), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), B. Schneider (LAM), L. Fuglsang (NOT), A. A. Djupvik (NOT), report on behalf of a larger collaboration: We observed the optical counterpart (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625) of the SVOM/ECLAIRs GRB 260515A (Brunet et al., GCN 44622) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. In a single 300-s exposure commencing on May 15.8696 UT (1.73 hr after trigger), the optical afterglow is well detected in our images, with an AB magnitude of r = 20.22 +- 0.04 (calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction). View this GCN Circular online at https://gcn.nasa.gov/circulars/44626. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42753] SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44625 SUBJECT: SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection DATE: 26/05/15 20:41:12 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> A.Sosnovskij, A.Kuznetsov, V.Lipunov, I.Panchenko, P.Balanutsa, K.Zhirkov, E.Gorbovskoy, G.Antipov, N.Tiurina, Ya.Kechin, V.Senik, A.Chasovnikov, V.Topolev,D.Vlasenko, A.Sankovich, I.Gorbunov, V.Fedorova, A.Telnova (Lomonosov MSU), N.Budnev, O.Gress (ISU), F.Podesta, M.J. Segura, C.Francile, R.Podesta, E. Gonzalez (OAFA, SJNU), D.Buckley (SAAO), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich (Blagoveschensk Educational StateUniversity) R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella, J.Tanori, L. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tavrida robotic telescope of MASTER Global Robotic Net [1-4] was pointed to the SVOM GRB260516A (Brunet et al. GCN 44622) error-box at 2026-05-15 19:19:18UT (notice time=2026-05-15 19:18:47) with upper limit up to 19.6m at single images. MASTER OT J151044.43+243321.7 / AT2026msu detection by Lomonosov MSU: MASTER-Tavrida auto-detection system discovered OT source at (RA, Dec) = 15h 10m 44.43s +24d 33m 21.7s on 2026-05-15.80648 UT. The OT magnitude (unfiltered) is 17.4m (mlim=19.1). The OT is seen in all images. There is no minor planet at this place. We have reference image on 2024-03-17.95291 UT with unfiltered mlim=19.5m. Spectral observations are required. Optical counterpart first was publishied by JinShan 100B Telescope (He et al. GCN 44623) and observed by Svom/VT (GCN 44624) Real time updated cover map and OT are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3316865 [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/44625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42752] GRB 260515A: SVOM/VT optical candidate from VHF data
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44624 SUBJECT: GRB 260515A: SVOM/VT optical candidate from VHF data DATE: 26/05/15 20:26:50 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi, J. T. Palmerio (CEA/Irfu), Y. L. Qiu, C. Wu, L. P. Xin (NAOC) on behalf of the SVOM/VT team. After the trigger by SVOM/ECLAIRs at 2026-05-15T19:08:19 UTC (T0), SVOM performed an automatic slew on the burst location (Brunet et al., GCN 44622). SVOM/VT began observing the field at 2026-05-15T19:12:34, 254.71 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 32: The position of this candidate is R.A., Dec. 227.6852, 24.5562 degrees, corresponding to: R.A. (J2000) = 15h10m44.4s Dec. (J2000) = 24d33m22.4s with an uncertainty of 0.50 arcsec. This location is consistent with the optical afterglow reported by He et al. (GCN 44623). This candidate was detected in both VT_R and VT_Band was flagged as an uncatalogued source. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | VT_B mag(AB) | VT_R mag(AB) | | -------------------- | ----------- | --------- | ------------- | ------------- | | 2026-05-15T19:12:34 | 5.08 min | 2*50 sec | 16.16 ± 0.01 | 15.78 ± 0.01 | Magnitudes were not corrected for Galactic reddening. The mean color of VT_B - VT_R = 0.38 is in line with the expectations of an event at redshift z < 4. 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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The Burst Advocate (BA) on shift for this alert is Andrea Saccardi: andrea.saccardi(a)cea.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42751] GRB 260515A: JinShan optical counterpart candidate
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44623 SUBJECT: GRB 260515A: JinShan optical counterpart candidate DATE: 26/05/15 19:51:51 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, Z.P. Zhu, X. Liu, D. Xu, J. An,S.Q. Jiang (NAOC), S.Y. Fu, A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report: We observed the field of GRB 260515A (sb26051504; Brunet et al., GCN 44622) using the JinShan 100B telescope located at Altay, Xinjiang, China. We obtained a series of frames in the Sloan i-band. An uncatalogued and varing source is detected within the EP/WXT/FXT error circle at coordinates R.A. (J2000) = 227.6852 deg Dec. (J2000) = 24.5562 deg with an uncertainty of ~ 1.0 arcsec. The source had i ~ 16.5 mag (optional: at a median time of ~ 11 min post-trigger, calibrated with Pan-STARRS DR2 and not corrected for Galactic extinction. We acknowledge the excellent support from T.Q. Chen, and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44623. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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