Suchergebnisse

Context. Long gamma-ray bursts (GRBs) give us the chance to study both their extreme physics and the star-forming galaxies in which they form. Aims. GRB 100418A, at a redshift of z = 0.6239, had a bright optical and radio afterglow, and a luminous star-forming host galaxy. This allowed us to study the radiation of the explosion as well as the interstellar medium of the host both in absorption and emission. Methods. We collected photometric data from radio to X-ray wavelengths to study the evolution of the afterglow and the contribution of a possible supernova (SN) and three X-shooter spectra obtained during the first 60 h. Results. The light curve shows a very fast gamma-ray burst: individual: GRB100418A; supernovae: individual: GRB100418A; galaxies: dwarf; ISM: abundances; ISM: kinematics and dynamicsoptical rebrightening, with an amplitude of ∼3 magnitudes, starting 2.4 h after the GRB onset. This cannot be explained by a standard external shock model and requires other contributions, such as late central-engine activity. Two weeks after the burst we detect an excess in the light curve consistent with a SN with peak absolute magnitude M = -18.5 mag, among the faintest GRB-SNe detected to date. The host galaxy shows two components in emission, with velocities differing by 130 km s, but otherwise having similar properties. While some absorption and emission components coincide, the absorbing gas spans much higher velocities, indicating the presence of gas beyond the star-forming regions. The host has a star formation rate of SFR = 12.2 M yr, a metallicity of 12 + log(O/H) = 8.55, and a mass of 1.6⊙ ×⊙ 10 M. Conclusions. GRB 100418A is a member of a class of afterglow light curves which show a steep rebrightening in the optical during the first day, which cannot be explained by traditional models. Its very faint associated SN shows that GRB-SNe can have a larger dispersion in luminosities than previously seen. Furthermore, we have obtained a complete view of the host of GRB 100418A owing to its spectrum, which contains a remarkable number of both emission and absorption lines.© ESO 2018. ; AdUP, CCT, KB, DAK, LI, and ZC acknowledge support from the Spanish Ministry of Economy and Competitivity under grant number AYA 2014-58381-P; in addition, AdUP and CCT from Ramon y Cajal fellowships (RyC-2012-09975 and RyC-2012-09984). DAK also acknowledges financial support from Juan de la Cierva Incorporacion fellowship IJCI-2015-26153. RF acknowledges support from European Regional Development Fund-Project >Engineering applications of microworld physics> (No. CZ.02.1.01/0.0/0.0/16_019/0000766). IB, IKh, RB, and SM acknowledge TUBITAK, IKI, KFU, and AST for partial support in using RTT150. This work was partially funded by the subsidy 3.6714.2017/8.9 allocated to Kazan Federal University for the state assignment in the sphere of scientific activities. TK acknowledges support from the DFG cluster of excellence >Origin and Structure of the Universe>. PS acknowledges support through the Sofja Kovalevskaja Award from the Alexander von Humboldt Foundation of Germany. RSR acknwoledges support from ASI (Italian Space Agency) through Contract n. 2015-046-R.0 and from European Union Horizon 2020 Programme under the AHEAD project (grant agreement n. 654215). The Cosmic Dawn Center is funded by the DNRF. Based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. This work is based on observations carried out under project number U051 with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. The UKIRT data were pipeline processed at the Cambridge Astronomical Survey Unit, and are archived at the Wide Field Astronomy Unit at the Royal Observatory Edinburgh This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.

We report the discovery and monitoring of the near-infrared counterpart (AT2017gfo) of a binary neutron-star merger event detected as a gravitational wave source by Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo (GW170817) and as a short gamma-ray burst by Fermi Gamma-ray Burst Monitor (GBM) and Integral SPI-ACS (GRB 170817A). The evolution of the transient light is consistent with predictions for the behavior of a "kilonova/macronova" powered by the radioactive decay of massive neutron-rich nuclides created via r-process nucleosynthesis in the neutron-star ejecta. In particular, evidence for this scenario is found from broad features seen in Hubble Space Telescope infrared spectroscopy, similar to those predicted for lanthanide-dominated ejecta, and the much slower evolution in the near-infrared ${K}_{{\rm{s}}}$-band compared to the optical. This indicates that the late-time light is dominated by high-opacity lanthanide-rich ejecta, suggesting nucleosynthesis to the third r-process peak (atomic masses $A\approx 195$). This discovery confirms that neutron-star mergers produce kilo-/macronovae and that they are at least a major—if not the dominant—site of rapid neutron capture nucleosynthesis in the universe. ; HST observations were obtained using programs GO 14771 (PI: Tanvir), GO 14804 (PI: Levan), and GO 14850 (PI: Troja). VLT observations were obtained using programs 099.D-0688, 099.D-0116, and 099.D-0622. N.R.T., K.W., P.T.O., J.L.O., and S.R. acknowledge support from STFC. A.J.L., D.S., and J.D.L. acknowledge support from STFC via grant ST/P000495/1. N.R.T. and A.J.L. have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement No. 725246, TEDE, Levan). Ad.U.P., C.T., Z.C., and D.A.K. acknowledge support from the Spanish project AYA 2014-58381-P. Z.C. also acknowledges support from the Juan de la Cierva Incorporacion fellowship IJCI-2014-21669, and D.A.K. from Juan de la Cierva Incorporacion fellowship IJCI-2015-26153. J.H. is supported by a VILLUM FONDEN Investigator grant (project number 16599). P.D.A., S.C., and A.M. acknowledge support from the ASI grant I/004/11/3. S.R. has been supported by the Swedish Research Council (VR) under grant No. 2016-03657_3, by the Swedish National Space Board under grant No. Dnr. 107/16, and by the research environment grant "Gravitational Radiation and Electromagnetic Astrophysical Transients (GREAT)" funded by the Swedish Research council (VR) under Dnr 2016-06012. P.A.E. acknowledges UKSA support. The VISTA observations were processed by C.G.F. at the Cambridge Astronomy Survey Unit (CASU), which is funded by the UK Science and Technology Research Council under grant ST/N005805/1. This research used resources provided by the Los Alamos National Laboratory Institutional Computing Program, which is supported by the U.S. Department of Energy National Nuclear Security Administration under contract No. DE-AC52-06NA25396. Based on observations made with the Nordic Optical Telescope (program 55-013, PI Pian), operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. ; Peer Reviewed