TITLE: GCN CIRCULAR NUMBER: 44512 SUBJECT: SVOM GRB 260509A: MASTER-OAFA optical observation DATE: 26/05/10 08:23:16 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru> Ya.Kechin (Lomonosov MSU), F.Podesta, M.J. Segura, C.Francile, R.Podesta, E. Gonzalez (OAFA, SJNU), A.Kuznetsov, V.Lipunov, I.Panchenko, P.Balanutsa, G.Antipov, N.Tiurina,K.Zhirkov, E.Gorbovskoy, V.Senik, A.Chasovnikov, V.Topolev, D.Vlasenko,A.Sankovich, I.Gorbunov(Lomonosov MSU), N.Budnev, O.Gress (ISU), 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-OAFA robotic telescope of MASTER Global Robotic Net [1-4] was pointed to the SVOM GRB260509A (trigger No 1778363469,11h 47m 32.88s , +00d 12m 34.2s, R=0.0786667 Gotz et al. GCN 44504) errorbox 8054 sec after notice time and 10202 sec after trigger time at 2026-05-10 00:41:11 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 31 deg. The sun altitude is -36.5 deg. MASTER-OAGH robotic telescope located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the SVOM GRB260509.91 errorbox 24424 sec after notice time (26572 sec after trigger time at 2026-05-10 05:14:01 UT), with upper limit up to 19.3 mag. The observations began at zenith distance = 36 deg. The sun altitude is -33.4 deg. The galactic latitude b = 59 deg., longitude l = 272 deg. There is MASTER OT J114735.9135.91+001717.7 optical counterpart at first images with m_OT~20.9 at 2026-05-10 00:41:11UT discovered by GOTO (O'Neill et al. GCN 44505) and observed by LCO (Saccardi et al. GCN 44506), SVOM|VT (Wu et al. GCN 44507), KAIT (Zheng et al. GCN 44510) Real time updated cover map and OT are available here: https://master.sai.msu.ru/site/master2/observ.php?id=3303991 MASTER upper limits: Tmid-T0 | Date Time | Site | Coord J2000) |Filt.| Expt. | Limit| Comment 10233 | 2026-05-10 00:41:11 | MASTER-OAFA | (11h 44m 48.88s , -00d 51m 54.0s) | C | 60 | 20.2 | 10293 | 2026-05-10 00:41:11 | MASTER-OAFA | (11h 44m 48.87s , -00d 51m 54.0s) | C | 180 | 20.5 | Coadd 10311 | 2026-05-10 00:42:29 | MASTER-OAFA | (11h 44m 48.21s , -00d 50m 56.7s) | C | 60 | 20.2 | 10389 | 2026-05-10 00:43:47 | MASTER-OAFA | (11h 44m 52.24s , -00d 51m 59.4s) | C | 60 | 20.2 | 10465 | 2026-05-10 00:45:03 | MASTER-OAFA | (11h 44m 46.21s , -00d 53m 02.8s) | C | 60 | 20.2 | 10525 | 2026-05-10 00:45:03 | MASTER-OAFA | (11h 44m 46.20s , -00d 53m 02.8s) | C | 180 | 20.5 | Coadd 10540 | 2026-05-10 00:46:19 | MASTER-OAFA | (11h 44m 52.06s , -00d 52m 51.7s) | C | 60 | 20.2 | 10618 | 2026-05-10 00:47:36 | MASTER-OAFA | (11h 44m 49.58s , -00d 51m 21.4s) | C | 60 | 20.2 | 10697 | 2026-05-10 00:48:55 | MASTER-OAFA | (11h 44m 49.29s , -00d 53m 05.6s) | C | 60 | 20.2 | 10757 | 2026-05-10 00:48:55 | MASTER-OAFA | (11h 44m 49.28s , -00d 53m 05.6s) | C | 180 | 20.4 | Coadd 10774 | 2026-05-10 00:50:12 | MASTER-OAFA | (11h 44m 52.95s , -00d 51m 27.6s) | C | 60 | 20.2 | 10852 | 2026-05-10 00:51:31 | MASTER-OAFA | (11h 44m 45.40s , -00d 52m 20.8s) | C | 60 | 20.2 | 10930 | 2026-05-10 00:52:48 | MASTER-OAFA | (11h 44m 45.82s , -00d 51m 24.8s) | C | 60 | 20.2 | 10990 | 2026-05-10 00:52:48 | MASTER-OAFA | (11h 44m 45.81s , -00d 51m 24.8s) | C | 180 | 20.4 | Coadd 11007 | 2026-05-10 00:54:06 | MASTER-OAFA | (11h 44m 49.85s , -00d 52m 28.2s) | C | 60 | 20.2 | 11086 | 2026-05-10 00:55:24 | MASTER-OAFA | (11h 44m 45.55s , -00d 53m 32.1s) | C | 60 | 20.2 | 11160 | 2026-05-10 00:56:39 | MASTER-OAFA | (11h 44m 49.59s , -00d 53m 31.6s) | C | 60 | 20.2 | 11220 | 2026-05-10 00:56:39 | MASTER-OAFA | (11h 44m 49.59s , -00d 53m 31.6s) | C | 180 | 20.4 | Coadd [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/44512. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...