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Title: r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE

Abstract

r-process nucleosynthesis in material ejected during neutron star mergers may lead to radioactively powered transients called kilonovae. The timescale and peak luminosity of these transients depend on the composition of the ejecta, which determines the local heating rate from nuclear decays and the opacity. Kasen et al. and Tanaka and Hotokezaka pointed out that lanthanides can drastically increase the opacity in these outflows. We use the new general-purpose nuclear reaction network SkyNet to carry out a parameter study of r-process nucleosynthesis for a range of initial electron fractions Y{sub e}, initial specific entropies s, and expansion timescales τ. We find that the ejecta is lanthanide-free for Y{sub e} ≳ 0.22−0.30, depending on s and τ. The heating rate is insensitive to s and τ, but certain, larger values of Y{sub e} lead to reduced heating rates, due to individual nuclides dominating the heating. We calculate approximate light curves with a simplified gray radiative transport scheme. The light curves peak at about a day (week) in the lanthanide-free (-rich) cases. The heating rate does not change much as the ejecta becomes lanthanide-free with increasing Y{sub e}, but the light-curve peak becomes about an order of magnitude brighter because it peaks muchmore » earlier when the heating rate is larger. We also provide parametric fits for the heating rates between 0.1 and 100 days, and we provide a simple fit in Y{sub e}, s, and τ to estimate whether or not the ejecta is lanthanide-rich.« less

Authors:
;  [1]
  1. TAPIR, Walter Burke Institute for Theoretical Physics, California Institute of Technology, MC 350-17, 1200 E California Boulevard, Pasadena CA 91125 (United States)
Publication Date:
OSTI Identifier:
22521772
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 815; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC ELECTRONS; COSMIC GAMMA BURSTS; COSMIC NEUTRONS; DIAGRAMS; ENTROPY; GRAVITATIONAL WAVES; HEATING RATE; LUMINOSITY; NEUTRON STARS; NUCLEAR DECAY; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; OPACITY; R PROCESS; RARE EARTHS; TRANSIENTS; VISIBLE RADIATION

Citation Formats

Lippuner, Jonas, and Roberts, Luke F., E-mail: jlippuner@tapir.caltech.edu. r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE. United States: N. p., 2015. Web. doi:10.1088/0004-637X/815/2/82.
Lippuner, Jonas, & Roberts, Luke F., E-mail: jlippuner@tapir.caltech.edu. r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE. United States. doi:10.1088/0004-637X/815/2/82.
Lippuner, Jonas, and Roberts, Luke F., E-mail: jlippuner@tapir.caltech.edu. Sun . "r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE". United States. doi:10.1088/0004-637X/815/2/82.
@article{osti_22521772,
title = {r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE},
author = {Lippuner, Jonas and Roberts, Luke F., E-mail: jlippuner@tapir.caltech.edu},
abstractNote = {r-process nucleosynthesis in material ejected during neutron star mergers may lead to radioactively powered transients called kilonovae. The timescale and peak luminosity of these transients depend on the composition of the ejecta, which determines the local heating rate from nuclear decays and the opacity. Kasen et al. and Tanaka and Hotokezaka pointed out that lanthanides can drastically increase the opacity in these outflows. We use the new general-purpose nuclear reaction network SkyNet to carry out a parameter study of r-process nucleosynthesis for a range of initial electron fractions Y{sub e}, initial specific entropies s, and expansion timescales τ. We find that the ejecta is lanthanide-free for Y{sub e} ≳ 0.22−0.30, depending on s and τ. The heating rate is insensitive to s and τ, but certain, larger values of Y{sub e} lead to reduced heating rates, due to individual nuclides dominating the heating. We calculate approximate light curves with a simplified gray radiative transport scheme. The light curves peak at about a day (week) in the lanthanide-free (-rich) cases. The heating rate does not change much as the ejecta becomes lanthanide-free with increasing Y{sub e}, but the light-curve peak becomes about an order of magnitude brighter because it peaks much earlier when the heating rate is larger. We also provide parametric fits for the heating rates between 0.1 and 100 days, and we provide a simple fit in Y{sub e}, s, and τ to estimate whether or not the ejecta is lanthanide-rich.},
doi = {10.1088/0004-637X/815/2/82},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 815,
place = {United States},
year = {2015},
month = {12}
}