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Spitzer mid-infrared detections of neutron star merger GW170817 suggests synthesis of the heaviest elements

Kasliwal, Mansi M. and Kasen, Daniel and Lau, Ryan M. and Perley, Daniel A. and Rosswog, Stephan and Ofek, Eran O. and Hotokezaka, Kenta and Chary, Ranga-Ram and Sollerman, Jesper and Goobar, Ariel and Kaplan, David L. (2022) Spitzer mid-infrared detections of neutron star merger GW170817 suggests synthesis of the heaviest elements. Monthly Notices of the Royal Astronomical Society: Letters, 510 (1). L7-L12. ISSN 1745-3925. doi:10.1093/mnrasl/slz007.

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We report our Spitzer Space Telescope observations and detections of the binary neutron star merger GW170817. At 4.5 μm, GW170817 is detected at 21.9  mag AB at +43 days and 23.9 mag AB at +74 days after merger. At 3.6 μm, GW170817 is not detected to a limit of 23.2 mag AB at +43 days and 23.1 mag AB at +74 days. Our detections constitute the latest and reddest constraints on the kilonova/macronova emission and composition of heavy elements. The 4.5 μm luminosity at this late phase cannot be explained by elements exclusively from the first abundance peak of the r-process. Moreover, the steep decline in the Spitzer band, with a power-law index of 3.4 ± 0.2, can be explained by a few of the heaviest isotopes with half-life around 14  d dominating the luminosity (e.g. ¹⁴⁰Ba, ¹⁴³Pr, ¹⁴⁷Nd, ¹⁵⁶Eu, ¹⁹¹Os, ²²³Ra, ²²⁵Ra, ²³³Pa, ²³⁴Th) or a model with lower deposition efficiency. This data offers evidence that the heaviest elements in the second and third r-process abundance peak were indeed synthesized. Our conclusion is verified by both analytics and network simulations and robust despite intricacies and uncertainties in the nuclear physics. Future observations with Spitzer and James Webb Space Telescope will further illuminate the relative abundance of the synthesized heavy elements.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kasliwal, Mansi M.0000-0002-5619-4938
Perley, Daniel A.0000-0001-8472-1996
Ofek, Eran O.0000-0002-6786-8774
Hotokezaka, Kenta0000-0002-2502-3730
Chary, Ranga-Ram0000-0001-7583-0621
Sollerman, Jesper0000-0003-1546-6615
Goobar, Ariel0000-0002-4163-4996
Kaplan, David L.0000-0001-6295-2881
Additional Information:© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Received: 13 October 2018; Revision received: 03 January 2019; Accepted: 03 January 2019; Published: 15 January 2019. This work was supported by the GROWTH (Global Relay of Observatories Watching Transients Happen) project funded by the National Science Foundation Partnership in International Research Program under NSF PIRE grant number 1545949. MMK and DK acknowledge stimulating discussions at KITP; this research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. DK is supported in part by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02–05CH11231 and DE-SC0017616, and by a SciDAC award DE-SC0018297. This research was supported in part by the Gordon and Betty Moore Foundation through Grant GBMF5076. MMK and EOO thank the United States-Israel Binational Science Foundation for BSF 2016227. We thank the anonymous referee for constructive feedback. We thank B. Metzger, J. L. Barnes, D. Siegel, G. Martinez-Pinedo, M. Wu, and R. Surman for valuable discussions.
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-05CH11231
Department of Energy (DOE)DE-SC0017616
Department of Energy (DOE)DE-SC0018297
Gordon and Betty Moore FoundationGBMF5076
Binational Science Foundation (USA-Israel)2016227
Subject Keywords:nucleosynthesis – gravitational waves – stars: neutron – infrared – gamma-ray burst: individual: GRB170817 – stars: individual: GW170817
Issue or Number:1
Record Number:CaltechAUTHORS:20190614-134342384
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Official Citation:Mansi M Kasliwal, Daniel Kasen, Ryan M Lau, Daniel A Perley, Stephan Rosswog, Eran O Ofek, Kenta Hotokezaka, Ranga-Ram Chary, Jesper Sollerman, Ariel Goobar, David L Kaplan, Spitzer mid-infrared detections of neutron star merger GW170817 suggests synthesis of the heaviest elements, Monthly Notices of the Royal Astronomical Society: Letters, Volume 510, Issue 1, February 2022, Pages L7–L12,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96450
Deposited By: George Porter
Deposited On:14 Jun 2019 21:55
Last Modified:17 Dec 2021 21:10

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