TITLE: GCN CIRCULAR NUMBER: 37941 SUBJECT: GRB 241029A: MASTER early optical counterpart detection DATE: 24/10/29 16:02:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), V.Lipunov, E.Gorbovskoy, N.Tiurina, D.Vlasenko, I.Panchenko, A.Kuznetsov (Lomonosov MSU), P.Balanutsa, G.Antipov, N.Tiurina, A.Sankovich, A.Sosnovskij, M.Gulyaev, Ya.Kechin, V.Senik (Lomonosov MSU), O.Gress, N.Budnev(ISU), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) 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 Global robotic net (http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L) started observation of Fermi GRB 241029A (GCN 37932, Ttrigger=02:19:59 UT) at MASTER-OAFA (Lipunov et al. GCN 37933, cover map https://master.sai.msu.ru/site/master2/observ.php?id=2652352 ) 66 sec after notice time (101 sec after trigger time) at 2024-10-29 02:21:41 UT. At first images (20s expositions) MASTER auto-detection system detected optical transient MASTER OT J214120.16+050453.4 at (RA, Dec) = 21h 41m 20.16s +05d 04m 53.4s on 2024-10-29.09839 UT. The OT magnitude (unfiltered) is ~13.4m (mlim=16.8). OT automatic light curve http://observ.pereplet.ru/GRB/MASTERGRB241029A_LC.jpg The OT is seen in 6 images. There is no minor planet at this place. We have reference image on 2017-05-29.35167 UT with unfiltered 18.3m. This OT was first publishied by Jiang et al. (GCN 37937, started at 09:49:01 UTC with m_OT=20.0 in R ) and continued by Weikang Lin et al. (GCN 37939), Jiang et al. GCN 37940. Observations in MASTER-Tunka and other MASTER Global Robotic Net telescopess will be continued.