Composition Effects on Kilonova Spectra and Light Curves. I

Journal Article · Fri Aug 07 00:00:00 EDT 2020 · The Astrophysical Journal (Online)

DOI:https://doi.org/10.3847/1538-4357/ab70b9· OSTI ID:1711378

Even, Wesley ^[1]; Korobkin, Oleg ^[2]; Fryer, Christopher L. ^[3]; Fontes, Christopher J. ^[4]; Wollaeger, R. T. ^[4]; Hungerford, Aimee ^[5]; Lippuner, Jonas ^[2]; Miller, Jonah ^[6]; Mumpower, Matthew R. ^[5]; Misch, G. Wendell ^[5]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Joint Inst. for Nuclear Astrophysics (JINA), East Lansing, MI (United States). Center for the Evolution of the Elements (JINA-CEE); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Southern Utah Univ., Cedar City, UT (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Joint Inst. for Nuclear Astrophysics (JINA), East Lansing, MI (United States). Center for the Evolution of the Elements (JINA-CEE); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Joint Inst. for Nuclear Astrophysics (JINA), East Lansing, MI (United States). Center for the Evolution of the Elements (JINA-CEE); Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Arizona, Tucson, AZ (United States); George Washington Univ., Washington, DC (United States); Univ. of New Mexico, Albuquerque, NM (United States)
4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Joint Inst. for Nuclear Astrophysics (JINA), East Lansing, MI (United States). Center for the Evolution of the Elements (JINA-CEE)
6. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Theoretical Astrophysics; Joint Inst. for Nuclear Astrophysics (JINA), East Lansing, MI (United States). Center for the Evolution of the Elements (JINA-CEE); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Nonlinear Studies (CNLS)

The merger of neutron star binaries is believed to eject a wide range of heavy elements into the universe. By observing the emission from this ejecta, scientists can probe the ejecta properties (mass, velocity, and composition distributions). The emission (a.k.a. kilonova) is powered by the radioactive decay of the heavy isotopes produced in the merger and this emission is reprocessed by atomic opacities to optical and infrared wavelengths. Understanding the ejecta properties requires calculating the dependence of this emission on these opacities. The strong lines in the optical and infrared in lanthanide opacities have been shown to significantly alter the light curves and spectra in these wavelength bands, arguing that the emission in these wavelengths can probe the composition of this ejecta. In this work, we study variations in the kilonova emission by varying individual lanthanide (and the actinide uranium) concentrations in the ejecta. The broad forest of lanthanide lines makes it difficult to determine the exact fraction of individual lanthanides. Nd is an exception. Its opacities above 1 μm are higher than other lanthanides and observations of kilonovae can potentially probe increased abundances of Nd. Similarly, at early times when the ejecta is still hot (first day), the U opacity is strong in the 0.2–1 μm wavelength range and kilonova observations may also be able to constrain these abundances.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1711378
• Alternate ID(s): OSTI ID: 23028397
• Report Number(s): LA-UR--19-23935
• Journal Information: The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 1 Vol. 899; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

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79 ASTRONOMY AND ASTROPHYSICS