Modeling Kilonova Light Curves: Dependence on Nuclear Inputs

Abstract

The mergers of binary neutron stars, as well as black hole-neutron star systems, are expected to produce an electromagnetic counterpart that can be analyzed to infer the element synthesis that occurred in these events. We investigate one source of uncertainties pertinent to lanthanide-rich outflows: the nuclear inputs to rapid neutron capture nucleosynthesis calculations. We begin by examining thirtytwo different combinations of nuclear inputs: eight mass models, two types of spontaneous fission rates and two types of fission daughter product distributions. We find that such nuclear physics uncertainties typically generate at least one order of magnitude uncertainty in key quantities such as the nuclear heating (one and a half orders of magnitude at one day post-merger), the bolometric luminosity (one order of magnitude at five days post-merger), and the inferred mass of material from the bolometric luminosity (factor of eight when considering the eight to ten day region). Since particular nuclear processes are critical for determining the electromagnetic signal, we provide tables of key nuclei undergoing β-decay, α-decay, and spontaneous fission important for heating at different times, identifying decays that are common among the many nuclear input combinations.

Interpolating Detailed Simulations of Kilonovae: Adaptive Learning and Parameter Inference Applications

“…We also find that although our detailed multifrequency opacities yield a more realistic representation of the physics in the system, the assumption of thermalization breaks down much sooner than anticipated. Uncertainties in nuclear physics can play a substantial role in kilonova light curves [7,8]. Given sufficient simulations, surrogate light curves can be constructed for a wide range of nuclear inputs.…”

“…The presence of matter is most unambiguously indicated by electromagnetic emission from nuclear matter ejected during the merger itself, which produces distinctive "kilonova" emission [3][4][5][6] via radioactive heating of this expanding material. Kilonova observations can provide insight into uncertain nuclear physics [7][8][9][10][11] and help constrain the expansion rate of the universe [12][13][14][15], particularly in conjunction with gravitational wave observations [2,[16][17][18][19][20][21][22].…”

The evolution of binary neutron star post-merger remnants: a review

“…Numerical simulations suggest that the total dynamical ejecta in a merger is in the range of 10 −4 − 10 −2 M with velocities in the range 0.1 − 0.3c [see e.g., 50] and a broad electron fraction distribution, Y e ∼ 0.1 − 0.4 [48] which dictates what elements can be synthesised from this ejecta, potentially up to an atomic mass number, A ∼ 195 [151,152]. We note that this is an area of active research, with significant uncertainties in many critical nuclear reaction quantities [153].…”

“…However, there are substantial quantitative uncertainties [e.g., 162] due to simplified neutrino treatments, numerical artifacts from limited resolution, and additional unmodelled processes such as a magnetised neutrino driven wind [e.g., 62]. Moreover, there are significant systematic uncertainties associated with nuclear reaction networks, opacities, etc., that can led to substantial bias in inferring properties of the kilonova from observations [153,163].…”