期刊
ASTROPHYSICAL JOURNAL
卷 815, 期 2, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/0004-637X/815/2/82
关键词
gamma-ray burst: general; gravitational waves; nuclear reactions, nucleosynthesis, abundances; stars: neutron
资金
- NSF MRI award [PHY-0960291]
- NSF/NCSA Blue Waters under allocation jr6 (NSF PRAC award) [ACI-1440083]
- NASA through an Einstein Postdoctoral Fellowship - Chandra X-ray Center [PF3-140114]
- NSF [TCAN AST-1333520, CAREER PHY-1151197, AST-1205732]
- Sherman Fairchild Foundation
- NASA [NAS8-03060]
- Direct For Computer & Info Scie & Enginr
- Office of Advanced Cyberinfrastructure (OAC) [1440083] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1333520] Funding Source: National Science Foundation
- Office of Advanced Cyberinfrastructure (OAC)
- Direct For Computer & Info Scie & Enginr [1440050] Funding Source: National Science Foundation
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 & 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-e, initial specific entropies s, and expansion timescales T. We find that the ejecta is lanthanide-free for Y-e greater than or similar to 0.22-0.30, depending on s and T. The heating rate is insensitive to s and T, but certain, larger values of Y-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-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-e, s, and T to estimate whether or not the ejecta is lanthanide-rich.
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