Spitzer mid-infrared detections of neutron star merger GW170817 suggests synthesis of the heaviest elements
Abstract
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.
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 (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_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.Attached Files
Published - slz007.pdf
Submitted - 1812.08708.pdf
Supplemental Material - slz007_supplemental_file.zip
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Additional details
- Eprint ID
- 96450
- Resolver ID
- CaltechAUTHORS:20190614-134342384
- OISE-1545949
- NSF
- PHY-1748958
- NSF
- DE-AC02-05CH11231
- Department of Energy (DOE)
- DE-SC0017616
- Department of Energy (DOE)
- DE-SC0018297
- Department of Energy (DOE)
- GBMF5076
- Gordon and Betty Moore Foundation
- 2016227
- Binational Science Foundation (USA-Israel)
- Created
-
2019-06-14Created from EPrint's datestamp field
- Updated
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2021-12-17Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC), Astronomy Department