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The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera

Soares-Santos, M. and Eifler, T. F. (2017) The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Discovery of the Optical Counterpart Using the Dark Energy Camera. Astrophysical Journal Letters, 848 (2). Art. No. L16. ISSN 2041-8213.

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We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational-wave emission, GW170817. Our observations commenced 10.5 hr post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hr post-merger we detected a bright optical transient located 10.”6 from the nucleus of NGC 4993 at redshift z = 0.0098, consistent (for H_0 = 70 km s^(−1) Mpc^(−1)) with the distance of 40 ± 8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes of I = 17.3 and z = 17.4, and thus an absolute magnitude of M_i = -15.7, in the luminosity range expected for a kilonova. We identified 1500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC 4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC 4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources.

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Soares-Santos, M.0000-0001-6082-8529
Eifler, T. F.0000-0002-1894-3301
Additional Information:© 2017 The American Astronomical Society. Received 2017 September 29; revised 2017 September 30; accepted 2017 October 1; published 2017 October 16. Funding for the DES Projects has been provided by the DOE and NSF (USA), MEC/MICINN/MINECO (Spain), STFC (UK), HEFCE (UK). NCSA (UIUC), KICP (U. Chicago), CCAPP (Ohio State), MIFPA (Texas A&M), CNPQ, FAPERJ, FINEP (Brazil), DFG (Germany), and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne Lab, UC Santa Cruz, University of Cambridge, CIEMAT-Madrid, University of Chicago, University College London, DES-Brazil Consortium, University of Edinburgh, ETH Zürich, Fermilab, University of Illinois, ICE (IEEC-CSIC), IFAE Barcelona, Lawrence Berkeley Lab, LMU München and the associated Excellence Cluster Universe, University of Michigan, NOAO, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Lab, Stanford University, University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES Data Management System is supported by the NSF under grant numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-88861, FPA2015-68048, and Centro de Excelencia SEV-2012-0234, SEV-2016-0597 and MDM-2015-0509. Research leading to these results has received funding from the ERC under the EU's 7th Framework Programme including grants ERC 240672, 291329 and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020. This Letter has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. H.Y.C., Z.D., B.F., M.F., and D.E.H. were partially supported by NSF CAREER grant PHY-1151836 and NSF grant PHYS-1708081. They were also supported by the Kavli Institute for Cosmological Physics at the University of Chicago through NSF grant PHY-1125897 and an endowment from the Kavli Foundation. The Berger Time-Domain Group at Harvard is supported in part by the NSF through grants AST-1411763 and AST-1714498, and by NASA through grants NNX15AE50G and NNX16AC22G. We thank the University of Copenhagen, DARK Cosmology Centre, and the Niels Bohr International Academy for hosting R.J.F., Z.D., and B.F. during the discovery of GW170817/SSS17a, where they were participating in the Kavli Summer Program in Astrophysics, "Astrophysics with gravitational wave detections." This program was supported by the Kavli Foundation, Danish National Research Foundation, the Niels Bohr International Academy, and the DARK Cosmology Centre. The UCSC group is supported in part by NSF grant AST–1518052, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, generous donations from many individuals through a UCSC Giving Day grant, and from fellowships from the Alfred P. Sloan Foundation and the David and Lucile Packard Foundation to R.J.F. We thank the CTIO director, Stephen Heathcote, for being supportive of our target of opportunity program using DECam. We also thank the CTIO staff for providing a great experience to observers on-site and remotely.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Ministerio de Educación y Ciencia (MEC)UNSPECIFIED
Ministerio de Ciencia e Innovación (MICINN)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
National Center for Supercomputing Applications (NCSA)UNSPECIFIED
Kavli Institute for Cosmological PhysicsUNSPECIFIED
Ohio State University Center for Cosmology and Astro-Particle PhysicsUNSPECIFIED
Mitchell Institute for Fundamental Physics and AstronomyUNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)UNSPECIFIED
Financiadora de Estudos e Projetos (FINEP)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
Collaborating Institutions in the Dark Energy SurveyUNSPECIFIED
Ministerio de Economía y Competitividad (MINECO)AYA2015-71825
Ministerio de Economía y Competitividad (MINECO)ESP2015-88861
Ministerio de Economía y Competitividad (MINECO)FPA2015-68048
Centro de Excelencia Severo OchoaSEV-2012-0234
Centro de Excelencia Severo OchoaSEV-2016-0597
Ministerio de Economía y Competitividad (MINECO)MDM-2015-0509
European Research Council (ERC)240672
European Research Council (ERC)291329
European Research Council (ERC)306478
Australian Research CouncilCE110001020
Department of Energy (DOE)DE-AC02-07CH11359
Kavli FoundationUNSPECIFIED
Danish National Research FoundationUNSPECIFIED
Niels Bohr International AcademyUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
University of California, Santa CruzUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:binaries: close – catalogs – gravitational waves – stars: neutron – surveys
Issue or Number:2
Record Number:CaltechAUTHORS:20171020-145145428
Persistent URL:
Official Citation:M. Soares-Santos et al 2017 ApJL 848 L16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82548
Deposited By: Tony Diaz
Deposited On:20 Oct 2017 22:28
Last Modified:09 Mar 2020 13:19

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