Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger
Abstract
The merger of two neutron stars has been predicted to produce an optical–infrared transient (lasting a few days) known as a 'kilonova', powered by the radioactive decay of neutron-rich species synthesized in the merger. Evidence that short γ-ray bursts also arise from neutron-star mergers has been accumulating. In models of such mergers, a small amount of mass (10^(−4)–10^(−2) solar masses) with a low electron fraction is ejected at high velocities (0.1–0.3 times light speed) or carried out by winds from an accretion disk formed around the newly merged object. This mass is expected to undergo rapid neutron capture (r-process) nucleosynthesis, leading to the formation of radioactive elements that release energy as they decay, powering an electromagnetic transient. A large uncertainty in the composition of the newly synthesized material leads to various expected colours, durations and luminosities for such transients. Observational evidence for kilonovae has so far been inconclusive because it was based on cases of moderate excess emission detected in the afterglows of γ-ray bursts. Here we report optical to near-infrared observations of a transient coincident with the detection of the gravitational-wave signature of a binary neutron-star merger and with a low-luminosity short-duration γ-ray burst20. Our observations, taken roughly every eight hours over a few days following the gravitational-wave trigger, reveal an initial blue excess, with fast optical fading and reddening. Using numerical models, we conclude that our data are broadly consistent with a light curve powered by a few hundredths of a solar mass of low-opacity material corresponding to lanthanide-poor (a fraction of 10^(−4.5) by mass) ejecta.
Additional Information
© 2017 Macmillan Publishers Limited, part of Springer Nature. Received 12 September; accepted 21 September 2017. Published online 16 October 2017. We are indebted to W. Rosing and the LCO staff for making these observations possible, and to the LIGO and Virgo science collaborations. We thank L. Singer, T. Piran and W. Fong for assistance with planning the LCO observing program. We appreciate assistance and guidance from the LIGO–Virgo Collaboration—Electromagnetic follow-up liaisons. We thank B. Tafreshi and G. M. Árnason for helping to secure Internet connections in Iceland while this paper was being reviewed. Support for I.A. and J.B. was provided by the National Aeronautics and Space Administration (NASA) through the Einstein Fellowship Program (via grant numbers PF6-170148 and PF7-180162, respectively). G.H., D.A.H. and C.M. are supported by US National Science Foundation (NSF) grant AST-1313484. D.P. and D.M. acknowledge support by Israel Science Foundation grant number 541/17. 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 US Department of Energy under contract number DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under contract number DE AC02-05CH11231. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The Digitized Sky Surveys were produced at the Space Telescope Science Institute (STScI) under US Government grant number NAG W-2166. The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council), until June 1988, and thereafter by the Anglo-Australian Observatory. Supplementary funding for sky-survey work at the STScI is provided by the European Southern Observatory. Author Contributions: I.A. is Principal Investigator of the LCO gravitational-wave follow-up program; he initiated and analysed the observations presented here and wrote the manuscript. G.H. helped with the LCO alert listener and ingestion pipeline, with follow-up observations and image analysis, and performed the blackbody fits. D.A.H. is the LCO–LIGO liaison, head of the LCO supernova group, and helped with the manuscript. C.M. assisted with obtaining and analysing data, and helped with the LCO alert listener. D.P. helped design the LCO follow-up program, assisted with the galaxy prioritization pipeline and contributed to the manuscript. D.K. and J.B. developed theoretical models and interpretations. M.Z. built the galaxy prioritization pipeline. S. Vasylyev built the LCO alert listener and ingestion pipeline. D.M. helped in discussions and with the manuscript. S. Valenti helped with image analysis and with the manuscript. Data availability: The photometric data that support the findings of this study are available in the Open Kilonova Catalog, https://kilonova.space. Source Data for Fig. 3 are provided with the online version of the paper. The authors declare no competing financial interests. Nature thanks R. Chevalier, C. Miller and the other anonymous reviewer(s) for their contribution to the peer review of this work.Attached Files
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Additional details
- Eprint ID
- 82420
- DOI
- 10.1038/nature24291
- Resolver ID
- CaltechAUTHORS:20171017-111646733
- NASA Einstein Fellowship
- PF6-170148
- NASA Einstein Fellowship
- PF7-180162
- NSF
- AST-1313484
- Israel Science Foundation
- 541/17
- Department of Energy (DOE)
- DE-SC0008067
- Department of Energy (DOE)
- DE-SC0017616
- Department of Energy (DOE)
- DE-SC0018297
- Department of Energy (DOE)
- DE-AC02-05CH11231
- NASA/JPL/Caltech
- NASA
- NAG W-2166
- Created
-
2017-10-17Created from EPrint's datestamp field
- Updated
-
2021-11-15Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)