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

MASTER OT J004207.99+405501.1/M31LRN 2015 luminous red nova in M31: Discovery, light curve, hydrodynamics and evolution

We report the discovery and multicolour (VRIW) photometry of the rare explosive star MASTEROT J004207.99+405501.1 - a luminous red nova - in theAndromeda galaxy M31N2015-01a. We use our original light curve acquired with identical MASTER Global Robotic Net telescopes in one photometric system: VRI during the first 30 d and W (unfiltered) during 70 d. Also, we added published multicolour photometry data to estimate the mass and energy of the ejected shell and we discuss the likely formation scenarios of outbursts of this type. We propose an interpretation of the explosion that is consistent with an evolutionary scenario where the merging of stellar components or the disruption of the common envelope of a close binary can explain some luminous red novae. Radiative hydrodynamic simulations of a luminous red nova were carried out in extended parameter space to fit its light curves. We find that the multicolour passband light curves of the luminous red nova are consistent with an initial common envelope radius of 10 R⊙, a merger mass of 3M⊙ and an explosion energy of 3 × 1048 erg. As a result, the phenomenon of novae consists of two classes: classical nuclear novae and more rare events (red novae) connected with the loss of compact common envelopes. © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society

Multiwavelength observations of GRB 140629A: A long burst with an achromatic jet break in the optical and X-ray afterglow

Aims. We investigate the long gamma-ray burst (GRB) 140629A through multiwavelength observations to derive the properties of the dominant jet and its host galaxy. Methods. The afterglow and host galaxy observations were taken in the optical (Swift/UVOT and various facilities worldwide), infrared (Spitzer), and X-rays (Swift/XRT) between 40 s and 3 yr after the burst trigger. Results. Polarisation observations by the MASTER telescope indicate that this burst is weakly polarised. The optical spectrum contains absorption features, from which we confirm the redshift of the GRB as originating at z = 2.276 ± 0.001. We performed spectral fitting of the X-rays to optical afterglow data and find there is no strong spectral evolution. We determine the hydrogen column density NH to be 7.2 × 1021 cm−2 along the line of sight. The afterglow in this burst can be explained by a blast wave jet with a long-lasting central engine expanding into a uniform medium in the slow cooling regime. At the end of energy injection, a normal decay phase is observed in both the optical and X-ray bands. An achromatic jet break is also found in the afterglow light curves ∼0.4 d after trigger. We fit the multiwavelength data simultaneously with a model based on a numerical simulation and find that the observations can be explained by a narrow uniform jet in a dense environment with an opening angle of 6.7◦ viewed 3.8◦ off-axis, which released a total energy of 1.4 × 1054 erg. Using the redshift and opening angle, we find GRB 140629A follows both the Ghirlanda and Amati relations. From the peak time of the light curve, identified as the onset of the forward shock (181s after trigger), the initial Lorentz factor (Γ0) is constrained in the range 82-118. Fitting the host galaxy photometry, we find the host to be a low mass, star-forming galaxy with a star formation rate of log (SFR) = 1.1+−00.94 M yr−1. We obtain a value of the neutral hydrogen density by fitting the optical spectrum, log NHI = 21.0 ± 0.3, classifying this host as a damped Lyman-alpha. High ionisation lines (N v, Si iv) are also detected in the spectrum. © ESO 2019.China Scholarship Council, CSCNational Science Foundation, NSFNational Basic Research Program of China (973 Program): DST/IMRCD/BRICS/Pilotcall/ProFCheap/2017, 2018YFA0404204, NSFC-1183300317-52-80133Agenzia Spaziale Italiana, ASI: 2015-046-R.0Ministry of Education and Science of the Russian Federation, Minobrnauka: 2019-05-595-0001-2496, 2019-05-592-0001-729317-52-80139 BRICS-aAgenzia Spaziale Italiana, ASI201406660015Leverhulme TrustEuropean Regional Development Fund, FEDER: AYA-2015-71718-RNational Research Foundation, NRF: 2018R1A2A1A05022685Horizon 2020 Framework Programme, H2020: 654215★ Research supported by the China Scholarship Council. † Deceased.7 IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation. http://ast.noao.edu/data/softwareAcknowledgements. Acknowledge the support by the program of China Scholarships Council (CSC) under the Grant no. 201406660015. We also acknowledge support from the Spanish MINEICO ministry and European FEDER funds AYA-2015-71718-R. SRO gratefully acknowledges the support of the Leverhulme Trust Early Career Fellowship. RS-R acknowledges support from ASI (Italian Space Agency) through the Contract no. 2015-046-R.0 and from European Union Horizon 2020 Programme under the AHEAD project (grant agreement no. 654215). MASTER equipment is supported by Lomonosov MSU Development Program and by Moscow Union OPTIKA. VL,EG, NT, VK are supported by BRICS RFBR grant 17-52-80133. MASTER-Tunka equipment is supported of Russian Federation Ministry of Science and High Education (grants 2019-05-592-0001-7293 and 2019-05-595-0001-2496). B.-B.Z. acknowledges support from the National Key Research and Development Program of China (2018YFA0404204), and NSFC-11833003. S.B.P. acknowledges BRICS grant DST/IMRCD/BRICS/Pilotcall/ProFCheap/2017(G) for this work. I.D. acknowledges L. Piro his invitation and financial support to visit and work at IAPS (Rome). We also acknowledge the use of the public data from the Swift data archive. We thank the excellent support form the GTC staff which is located at Observatorio del Roque de los Muchachos at Canary Islands (Spain). Thanks to the data support by NASA with Spitzer Space Telescope. SP and RB acknowledge support from RBRF grant 17-52-80139 BRICS-a. IHP acknowledges support from NRF 2018R1A2A1A05022685. Finally, we want to thank the anonymous referee for his/her comments, which have substantially improved the manuscript

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