Correlations of r-Process Elements in Very Metal-Poor Stars as Clues to their Nucleosynthesis Sites

Farouqi, Khalil; Thielemann, Friedrich-Karl; Rosswog, Stephan; Kratz, Karl-Ludwig

doi:10.48550/arxiv.2107.03486

Cited by 9 publications

(14 citation statements)

References 174 publications

(283 reference statements)

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“…The lighter r -process as observed in metal-poor stars, exhibits variation on the order of 1 dex, while the "strong" r -process pattern varies by only about 0.3 dex [9]. An investigation with more accurate numbers based on careful statistical analysis of observations will be the subject of future studies [52].…”

Section: Resultsmentioning

confidence: 92%

Constraining inputs to realistic kilonova simulations through comparison to observed r-process abundances

Ristic¹,

Holmbeck²,

Wollaeger³

et al. 2022

Preprint

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Kilonovae, one source of electromagnetic emission associated with neutron star mergers, are powered by the decay of radioactive isotopes in the neutron-rich merger ejecta. Models for kilonova emission consistent with available modeling and the electromagnetic counterpart to GW170817 also predict characteristic abundance patterns, determined by the relative balance of different types of material in the outflow. Assuming the observed source is prototypical, this inferred abundance pattern in turn must match r -process abundances deduced by other means, such as what is observed in the solar system. We report on analysis comparing the input mass-weighted elemental compositions adopted in our radiative transfer simulations to the mass fractions of elements in the Sun. We characterise the extent to which our parameter inference results depend on our assumed composition for the dynamical and wind ejecta and examine how the new results compare to previous work. We find that a mass ratio of Mw/M d = 2.81 reproduces the observed AT2017gfo kilonova light curves while also producing the abundance of neutron-capture elements in the solar system.

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Section: Resultsmentioning

confidence: 92%

Constraining inputs to realistic kilonova simulations through comparison to observed r-process abundances

Ristic¹,

Holmbeck²,

Wollaeger³

et al. 2022

Preprint

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show abstract

“…Overall, the small amount of ejecta underlines the need for additional ejection channels such as torus unbinding or neutrino-driven winds in order to reach the ejecta masses estimated for GW170817. The matter being predominantly ejected via shocks probably means that its electron fraction is increased with respect to the cold, β-equilibrium values inside the original neutron stars (∼ 0.05; see, e.g., Figure 21 in [120]). Again consistent with earlier studies, we found that the softer equation of state cases eject more mass and also reducing the exponent γ th seems to enhance mass ejection.…”

Section: Discussionmentioning

confidence: 99%

Thinking Outside the Box: Numerical Relativity with Particles

2022

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The observation of gravitational waves from compact objects has now become an active part of observational astronomy. For a sound interpretation, one needs to compare such observations against detailed Numerical Relativity simulations, which are essential tools to explore the dynamics and physics of compact binary mergers. To date, essentially all simulation codes that solve the full set of Einstein’s equations are performed in the framework of Eulerian hydrodynamics. The exception is our recently developed Numerical Relativity code SPHINCS_BSSN which solves the commonly used BSSN formulation of the Einstein equations on a structured mesh and the matter equations via Lagrangian particles. We show here, for the first time, SPHINCS_BSSN neutron star merger simulations with piecewise polytropic approximations to four nuclear matter equations of state. In this set of neutron star merger simulations, we focus on perfectly symmetric binary systems that are irrotational and have 1.3 M⊙ masses. We introduce some further methodological refinements (a new way of steering dissipation, an improved particle–mesh mapping), and we explore the impact of the exponent that enters in the calculation of the thermal pressure contribution. We find that it leaves a noticeable imprint on the gravitational wave amplitude (calculated via both quadrupole approximation and the Ψ4 formalism) and has a noticeable impact on the amount of dynamic ejecta. Consistent with earlier findings, we only find a few times 10−3M⊙ as dynamic ejecta in the studied equal mass binary systems, with softer equations of state (which are more prone to shock formation) ejecting larger amounts of matter. In all of the cases, we see a credible high-velocity (∼0.5…0.7c) ejecta component of ∼10−4M⊙ that is launched at contact from the interface between the two neutron stars. Such a high-velocity component has been suggested to produce an early, blue precursor to the main kilonova emission, and it could also potentially cause a kilonova afterglow.

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“…Fig. 21 in [109]). Again consistent with earlier studies, we find that the softer equation of state cases eject more mass and also reducing the exponent γ th seems to enhance mass ejection.…”

Section: Discussionmentioning

confidence: 97%

Thinking outside the box: Numerical Relativity with particles

Rosswog¹,

Diener²,

Torsello³

2022

Preprint

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The observation of gravitational waves from compact objects has now become an active part of observational astronomy. For a sound interpretation, one needs to compare such observations against detailed Numerical Relativity simulations, which are essential tools to explore the dynamics and physics of compact binary mergers. To date, essentially all simulation codes that solve the full set of Einstein's equations are performed in the framework of Eulerian hydrodynamics. The exception is our recently developed Numerical Relativity code SPHINCS_BSSN which solves the commonly used BSSN formulation of Einstein equations on a structured mesh and the matter equations via Lagrangian particles. We show here, for the first time, SPHINCS_BSSN neutron star merger simulations with piecewise polytropic approximations to four nuclear matter equations of state. We introduce some further methodological refinements (a new way of steering dissipation, an improved particlemesh mapping) and we explore the impact of the exponent that enters in the calculation of the thermal pressure contribution. We find that it leaves a noticeable imprint on the gravitational wave amplitude (calculated via both quadrupole approximation and the Ψ 4 -formalism) and has a noticeable impact on the amount of dynamic ejecta. Consistent with earlier findings, we only find a few times 10 −3 M as dynamic ejecta in the studied equal mass binary systems, with softer equations of state (which are more prone to shock formation) ejecting larger amounts of matter. We also see a credible high-velocity (∼ 0.5..0.7c) ejecta component of ∼ 10 −4 M in all our cases. Such a high-velocity component has been suggested to produce an early, blue precursor to the main kilonova emission and it could also potentially cause a kilonova afterglow.

show abstract

Correlations of r-Process Elements in Very Metal-Poor Stars as Clues to their Nucleosynthesis Sites

Cited by 9 publications

References 174 publications

Constraining inputs to realistic kilonova simulations through comparison to observed r-process abundances

Constraining inputs to realistic kilonova simulations through comparison to observed r-process abundances

Thinking Outside the Box: Numerical Relativity with Particles

Thinking outside the box: Numerical Relativity with particles

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