Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis

Creators: Drout, M. R.; Piro, A. L.; Shappee, B. J.; Kilpatrick, C. D.; Simon, J. D.; Contreras, C.; Coulter, D. A.; Foley, R. J.; Siebert, M. R.; Morrell, N.; Boutsia, K.; Di Mille, F.; Holoien, T. W.-S.; Kasen, D.; Kollmeier, J. A.; Madore, B. F.; Monson, A. J.; Murguia-Berthier, A.; Pan, Y.-C.; Prochaska, J. X.; Ramirez-Ruiz, E.; Rest, A.; Adams, C.; Alatalo, K.; Bañados, E.; Baughman, J.; Beers, T. C.; Bernstein, R. A.; Bitsakis, T.; Campillay, A.; Hansen, T. T.; Higgs, C. R.; Ji, A. P.; Maravelias, G.; Marshall, J. L.; Bidin, C. Moni; Prieto, J. L.; Rasmussen, K. C.; Rojas-Bravo, C.; Strom, A. L.; Ulloa, N.; Vargas-González, J.; Wan, Z.; Whitten, D. D.

Abstract

On 17 August 2017, gravitational waves were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identified as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days post-merger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in r-process nucleosynthesis in the universe.

Additional Information

© 2017 American Association for the Advancement of Science. Received for publication September 20, 2017. Accepted for publication October 11, 2017. We thank J. Mulchaey (Carnegie Observatories), L. Infante (Las Campanas Observatory), and the entire Las Campanas Observatory staff for their dedication, professionalism, and excitement, which were all critical in obtaining the observations used in this study. We also thank I. Thompson and the Carnegie Observatory Time Allocation Committee for approving the Swope Supernova Survey and scheduling our program. We thank the University of Copenhagen, Dark Cosmology Centre, and the Niels Bohr International Academy for hosting D.A.C., R.J.F., A.M.B., E.R., and M.R.S. during this work. R.J.F., A.M.B., and E.R. 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. M.R.D., B.J.S., K.A.A., and A.P.J. were supported by NASA through Hubble Fellowships awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. M.R.D. is a Hubble and Carnegie-Dunlap Fellow. M.R.D. acknowledges support from the Dunlap Institute at the University of Toronto, and thanks M. W. B. Wilson, L. Z. Kelly, C. McCully, and R. Margutti for helpful discussions. The University of California, Santa Cruz (UCSC) group is supported in part by NSF grant AST-1518052; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; generous donations from many individuals through a UCSC Giving Day grant; and fellowships from the Alfred P. Sloan Foundation (R.J.F), the David and Lucile Packard Foundation (R.J.F. and E.R.), and the Niels Bohr Professorship from the DNRF (E.R.). D.K. is supported in part by a Department of Energy (DOE) Early Career award DE-SC0008067, a DOE Office of Nuclear Physics award DE-SC0017616, and a DOE SciDAC award DE-SC0018297, and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Divisions of Nuclear Physics, of the U.S. Department of Energy under contract No.DE-AC02-05CH11231. Support for J.L.P. is in part provided by FONDECYT through grant 1151445 and by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. C.M.B. was supported by FONDECYT through regular project 1150060. G.M. acknowledges support from CONICYT, Programa de Astronomía/PCI, FONDO ALMA 2014, Proyecto no. 31140024. A.M.B. acknowledges support from a UCMEXUS-CONACYT Doctoral Fellowship. C.A. was supported by the California Institute of Technology through a Summer Undergraduate Research Fellowship (SURF) with funding from the Associates SURF Endowment. T.C.B., K.C.R., and D.D.W. acknowledge partial support for this work from grant PHY 14-30152; Physics Frontier Center/Joint Institute for Nuclear Astrophysics Center for the Evolution of the Elements (JINA-CEE), awarded by the U.S. National Science Foundation, and from the Luksic Foundation. J.X.P. is also affiliated with the Kavli Institute for the Physics and Mathematics of the Universe. This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. This work is based in part on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, as part of PESSTO (the Public ESO Spectroscopic Survey for Transient Objects Survey) through ESO program 199.D-0143. 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 NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very important cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and NSF. The Magellan/du Pont data presented in this work and code used to perform the analysis are available via http or anonymous ftp at http://data.obs.carnegiescience.edu/SSS17a. The Swope data of SSS17a are available at https://ziggy.ucolick.org/sss17a/. ESO and Swift-UVOT data analyzed in this work are available at http://archive.eso.org/eso/eso_archive_main.html (program ID 199.D-0143) and https://archive.stsci.edu/swiftuvot/search.php (target IDs 12167, 12978, and 12979), respectively. Reduced photometry is presented in table S1 and is also available on the Open Kilonova Catalog (53) (https://kilonova.space).

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