MASTER Global Robotic Net is supported in part by the Development Programme of Lomonosov Moscow State University. This work was also supported in part by RFBR 15-02-07875 grant. This work is also partially supported by the Russian Federation Ministry of Education and Science (agreement 14.B25.31.0010 and government assignment 2014/51, project 1366) and by state order No. 3.615.2014/K in relation to scientific activity (design part). The Fermi GBM collaboration acknowledges support for GBM development, operations, and data analysis from NASA in the U.S.A and BMWi/DLR in Germany. AG is supported by an appointment to the NASA Postdoctoral Program at MSFC, administered by Oak Ridge Associated Universities through a contract with NASA. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. This research has made use of NASA's Astrophysics Data System. The Fermi GBM collaboration acknowledges support for GBM development, operations, and data analysis from NASA in the United States and BMWi/DLR in Germany. AG is supported by an appointment to the NASA Postdoctoral Program at MSFC, administered by Oak Ridge Associated Universities through a contract with NASA. This work was supported in part by Russian Foundation of Fundamental Research, grant RFBR 14-02-31546, 14-02-91172. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. This research has made use of NASA's Astrophysics Data System. The KW experiment is partially supported by a Russian Space Agency contract, RFBR grants 15-02-00532a and 13-02-12017 ofi-m. Part of the funding for GROND (both hardware and personnel) was generously granted from the Leibniz-Prize to Professor G. Hasinger (DFG grant HA 1850/28-1). AJC acknowledges support from the Spanish Ministry Grant AYA 2012-39727-C03-01. The data presented here were obtained in part with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. CD acknowledges support through EXTraS, funded from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 607452. DAK, SK, and SS acknowledge support by DFG grants Kl 766/16-1 and 766/16-3. In addition, SS acknowledges support by the Thüringer Ministerium für Bildung, Wissenschaft und Kultur under FKZ 12010-514. We acknowledge A. Burenkov, V. Vlasyuk and T. Fatkhullin for the help in observations. AM, VK and TS are partially supported by the Research Program OFN-17 of the Division of Physics, Russian Academy of Sciences. AM is also partially supported by the grant MK-1699.2014.2 of the President of Russian Federation and by RFBR 14-32-50547. SS acknowledges support from CONICYT-Chile FONDECYT 3140534, Basal-CATA PFB-06/2007, and Project IC120009 ‘Millennium Institute of Astrophysics (MAS) of Iniciativa Científica Milenio del Ministerio de Economía, Fomento y Turismo’.

We report the early discovery of the optical afterglow of gamma-ray burst (GRB) 140801A in the 137 deg 3-σ error-box of the Fermi Gamma-ray Burst Monitor (GBM). MASTER is the only observatory that automatically reacts to all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart was discovered solely from its GBM localization. The optical afterglow of GRB 140801A was found by MASTER Global Robotic Net 53 s after receiving the alert, making it the fastest optical detection of a GRB from a GBM error-box. Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m Big Telescope Alt-azimuth of the Special Astrophysical Observatory of the Russian Academy of Sciences reveals a redshift of z = 1.32. We performed optical and near-infrared photometry of GRB 140801A using different telescopes with apertures ranging from 0.4 to 10.4 m. GRB 140801A is a typical burst in many ways. The rest-frame bolometric isotropic energy release and peak energy of the burst are E = 5.54 × 10 erg and E ≃280 keV, respectively, which is consistent with the Amati relation. The absence of a jet break in the optical light curve provides a lower limit on the half-opening angle of the jet θ = 6.° 1. The observed E is consistent with the limit derived from the Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis show that GRB 140801A could belong to the class of intermediate duration. The rapid detection of the optical counterpart of GRB 140801A is especially important regarding the upcoming experiments with large coordinate error-box areas. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Lipunov, V. M. et al.--Full list of authors: Lipunov, V. M.; Gorosabel, J.; Pruzhinskaya, M. V.; de Ugarte Postigo, A.; Pelassa, V.; Tsvetkova, A. E.; Sokolov, I. V.; Kann, D. A.; Xu, Dong; Gorbovskoy, E. S.; Krushinski, V. V.; Kornilov, V. G.; Balanutsa, P. V.; Boronina, S. V.; Budnev, N. M.; Cano, Z.; Castro-Tirado, A. J.; Chazov, V. V.; Connaughton, V.; Delvaux, C.; Frederiks, D. D.; Fynbo, J. F. U.; Gabovich, A. V.; Goldstein, A.; Greiner, J.; Gress, O. A.; Ivanov, K. I.; Jakobsson, P.; Klose, S.; Knust, F.; Komarova, V. N.; Konstantinov, E.; Krylov, A. V.; Kuvshinov, D. A.; Kuznetsov, A. S.; Lipunova, G. V.; Moskvitin, A. S.; Pal'shin, V. D.; Pandey, S. B.; Poleshchuk, V. A.; Schmidl, S.; Sergienko, Yu. P.; Sinyakov, E. V.; Schulze, S.; Sokolov, V. V.; Sokolova, T. N.; Sparre, M.; Thöne, C. C.; Tlatov, A. G.; Tyurina, N. V.; Ulanov, M. V.; Yazev, S. A.; Yurkov, V. V.

Peer reviewed