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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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[vsnet-grb-info 42750] GRB 260515A: SVOM detection of a burst
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44622 SUBJECT: GRB 260515A: SVOM detection of a burst DATE: 26/05/15 19:36:12 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, L. Bouchet (IRAP), A. Saccardi (CEA/Irfu), D. Gotz (CEA/Irfu) report on behalf of the SVOM mission team: At 2026-05-15T19:08:19 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260515A (SVOM burst-id sb26051504). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 17 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 24.06 in the [5-20] keV energy band over a time window of 10.20 seconds starting at 2026-05-15T19:08:19. The localization of the best alert is R.A., Dec. 227.6800, 24.5706 degrees: R.A. (J2000) = 15h10m43.20s Dec. (J2000) = 24d34m14.13s with a 90% confidence level (C.L.) radius of 3.77 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single peak structure with a T90 duration of 16.6 +/-1.5 s in the 5-120 keV. This burst was also detected by SVOM/GRM with a significance of 10.2 . SVOM slewed to the burst. MXT and VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Andrea Saccardi (CEA): 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/44622. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42749] GRB 260510C: Glowbug gamma-ray detection
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44621 SUBJECT: GRB 260510C: Glowbug gamma-ray detection DATE: 26/05/15 18:39:46 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260510C, which was detected by Fermi/GBM (GCN 44520, 44564), SVOM (GCN 44521), MAXI/GSC (GCN 44526), AstroSat/CZTI (GCN 44544), and CALET (GCN 44616). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-10 17:15:37.096 with a duration of 4.1 s and a total significance of about 5.2 sigma. The lightcurve comprises a single peak corresponding to the portion of the burst observed by CALET/CGBM (GCN 44616). The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42748] IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44620 SUBJECT: IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility DATE: 26/05/15 18:10:11 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260504A (IceCube Collaboration, GCN 44464) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-05-07 04:25 UTC, approximately 55.2 hours after event time due to bad weather. We covered 68.2% (0.6 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 30s with a typical depth of 20.5 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/44620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42747] EP260514a: GROWTH-India Telescope optical upper limit
by GCN Circulars 15 May '26

15 May '26

TITLE: GCN CIRCULAR NUMBER: 44619 SUBJECT: EP260514a: GROWTH-India Telescope optical upper limit DATE: 26/05/15 17:20:18 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan (IITB), V. Vijaykumar (IITB), V. Swain (IITB), D. Eappachen (IIA), A.P. Saikia (IITB), S. Patil (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP260514a (Cheng et al., GCN 44613), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-05-15 16:27:06 (UTC), i.e., 0.98 days after the trigger, and obtained single exposure in the r' filter. We did not detect any transient in our image within the WXT localization region. The photometric upper limit is as follows: | MJD (mid) | Filter | tmid-t0 (hour) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | -------------- | ------------------- | ---------------- | | 61175.68756 | r' | 23.57 | 360 | 20.5 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our results are consistent with other optical observation (Lipunov et al., GCN 44614). 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/44619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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