Prompt, early, and afterglow optical observations of five gamma-ray bursts (GRBs 100901A, 100902A, 100905A, 100906A, and 101020A)

We present results of the prompt, early, and afterglow optical observations of five gamma-ray bursts, GRBs 100901A, 100902A, 100905A, 100906A, and 101020A, made with the Mobile Astronomical System of TElescope-Robots in Russia (MASTER-II net), the 1.5-m telescope of Sierra-Nevada Observatory, and the 2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A, we detected optical counterparts and obtained light curves starting before cessation of gamma-ray emission, at 113 s and 48 s after the trigger, respectively. Observations of GRB 100906A were conducted with two polarizing filters. Observations of the other three bursts gave the upper limits on the optical flux; their properties are briefly discussed. More detailed analysis of GRB 100901A and GRB 100906A supplemented by Swift data provides the following results and indicates different origins of the prompt optical radiation in the two bursts. The light curves patterns and spectral distributions suggest a common production site of the prompt optical and high-energy emission in GRB 100901A. Results of spectral fits for GRB 100901A in the range from the optical to X-rays favor power-law energy distributions with similar values of the optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking optical light curve suggesting that the prompt optical radiation in this GRB originated in a front shock. This is supported by a spectral analysis. We have found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. An upper limit on the value of the optical extinction on the host of GRB 100906A is obtained.Comment: 18 pages, 14 figures, 14 tables, 5 machine readable tables; accepted for publication in MNRA

Early polarization observations of the optical emission of gamma-ray bursts: GRB 150301B and GRB 150413A

We report early optical linear polarization observations of two gamma-ray burstsmade with the MASTER robotic telescope network. We found the minimum polarization for GRB 150301B to be 8 per cent at the beginning of the initial stage, whereas we detected no polarization for GRB 150413A either at the rising branch or after the burst reached the power-law afterglow stage. This is the earliest measurement of the polarization (in cosmological rest frame) of gamma-ray bursts. The primary intent of the paper is to discover optical emission and publish extremely rare (unique) high-quality light curves of the prompt optical emission of gammaray bursts during the non-monotonic stage of their evolution. We report that our team has discovered the optical counterpart of one of the bursts, GRB 150413A.Fil: Gorbovskoy, E.S.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Lipunov, V.M.. Lomonosov Moscow State University; . Moscow State University; RusiaFil: Buckley, D. A. H.. South African Astronomical Observatory; SudáfricaFil: Kornilov, V. G.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Balanutsa, P. V.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Tyurina, N. V.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Kuznetsov, A. S.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Kuvshinov, D. A.. Lomonosov Moscow State University; Rusia. Moscow State University; RusiaFil: Gorbunov, I. A.. Lomonosov Moscow State University ; Rusia. Sternberg Astronomical Institute, Moscow State University; RusiaFil: Vlasenko, D.. Lomonosov Moscow State University; RusiaFil: Popova, E.. Lomonosov Moscow State University; Ruanda. Sternberg Astronomical Institute; RusiaFil: Chazov, V. V.. Sternberg Astronomical Institute; Rusia. Lomonosov Moscow State University; RusiaFil: Potter, S.. South African Astronomical Observatory; SudáfricaFil: Kotze, M.. South African Astronomical Observatory; SudáfricaFil: Kniazev, A. Y.. South African Astronomical Observatory; Sudáfrica. Southern African Large Telescope Foundation; SudáfricaFil: Gress, O. A.. Irkutsk State University; RusiaFil: Budnev, N. M.. Irkutsk State University; RusiaFil: Ivanov, K. I.. Irkutsk State University; RusiaFil: Yazev, S. A.. Irkutsk State University; RusiaFil: Tlatov, A. G.. Kislovodsk Solar Station of the Pulkovo Observatory RAS; RusiaFil: Senik, V. A.. Lomonosov Moscow State University; Rusia. Sternberg Astronomical Institute; Rusia. Kislovodsk Solar Station of the Pulkovo Observatory RAS; RusiaFil: Dormidontov, D. V.. Lomonosov Moscow State University; Rusia. Sternberg Astronomical Institute; Rusia. Kislovodsk Solar Station of the Pulkovo Observatory RAS; RusiaFil: Parhomenko, A. V.. Lomonosov Moscow State University; . Pulkovo Observatory Of The Russian Academy Of Sciences; . Sternberg Astronomical Institute; RusiaFil: Krushinski, V. V.. Kislovodsk Solar Station of the Pulkovo Observatory RAS; RusiaFil: Zalozhnich, I. S.. Kislovodsk Solar Station of the Pulkovo Observatory RAS; RusiaFil: Castro Tirado, R. Alberto. Consejo Superior de Investigaciones Científicas; EspañaFil: Sánchez Ramírez, R.. Consejo Superior de Investigaciones Científicas; EspañaFil: Sergienko, Yu.P.. Blagoveschensk Educational State University; RusiaFil: Gabovich, A.. Blagoveschensk Educational State University; RusiaFil: Yurkov, V.V.. Blagoveschensk Educational State University; RusiaFil: Levato, Orlando Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Mallamaci, Claudio Carlos. Observatorio Astronmico Félix Aguilar; ArgentinaFil: Lopez, C.. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Informática. Observatorio Astronómico Félix Aguilar; ArgentinaFil: Podesta, F.. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Departamento de Informática. Observatorio Astronómico Félix Aguilar; ArgentinaFil: Vladimirov, V. V.. Lomonosov Moscow State University; Rusia. Sternberg Astronomical Institute, Moscow State University; Rusi