νbhlight: Radiation GRMHD for Neutrino-driven Accretion Flows

Miller, Jonah; Ryan, Benjamin R.; Dolence, Joshua C.

doi:10.3847/1538-4365/ab09fc

Cited by 37 publications

(44 citation statements)

References 59 publications

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“…We captured the output flux from the accretion disk simulations with νbhlight [16] as initial data for the kilonova expansion. [15]. The velocity is sampled at the times when particles exit the outflow boundary of the spherical grid.…”

Section: Astrophysical Modelmentioning

confidence: 99%

“…There are several mechanisms that can unbind neutron-rich matter from a BNS merger [14]. Here, we focus on the wind ejecta from a post-merger accretion disk [15]. Such a disk is left after the central hypermassive merger remnant collapses to a BH.…”

Section: Introductionmentioning

confidence: 99%

“…Our pipeline incorporates several state-of-the art tools developed at Los Alamos National Laboratory (LANL) to tackle different facets of the problem. The most realistic, state-ofthe art morphologies for accretion disk wind and ejecta to date have been recently provided by Miller et al [15] who used the νbhlight code [16] to simulate the disk dynamics in a fixed general-relativistic background including Monte-Carlo neutrino transport. This simulation required approximately 400 cores for 3 weeks of walltime.…”

Section: Introductionmentioning

confidence: 99%

“…Figure1: Initial distribution of the electron fraction (number of electrons per nucleon) for accretion disk ejecta in velocity space[15]. The velocity is sampled at the times when particles exit the outflow boundary of the spherical grid.…”

mentioning

confidence: 99%

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Realistic Kilonova Up Close

Stewart¹,

Lo²,

Korobkin³

et al. 2022

Preprint

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Neutron star mergers are cosmic catastrophes that produce some of the most energetic observed phenomena: short gamma-ray bursts, gravitational wave signals, and kilonovae. The latter are optical transients, powered by radioactive nuclides which are synthesized when the neutron-rich ejecta of a disrupted neutron star undergoes decompression. We model this decompression phase using data from simulations of post-merger accretion disk winds. We use smoothed particle hydrodynamics with realistic nuclear heating to model the expansion over multiple scales, from initially several thousand km to billions of km. We then render a realistic image of a kilonova ejecta as it would appear for a nearby observer. This is the first time such a visualization is performed using input from state-of-the-art accretion disk simulations, nuclear physics and atomic physics. The volume rendering in our model computes an opacity transfer function on the basis of the physical opacity, varying significantly with the inhomogeneity of the neutron richness in the ejecta. Other physical quantities such as temperature or electron fraction can be visualized using an independent color transfer function. We discuss several difficulties with the ParaView application that we encountered during the visualization process, and give descriptions of our solutions and workarounds which could be used for future improvements.

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Section: Astrophysical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Realistic Kilonova Up Close

Stewart¹,

Lo²,

Korobkin³

et al. 2022

Preprint

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“…The relevant radiation transfer problem must be solved, taking into account frequency dependence and directionality. In current models this is done at different levels of sophistication, starting from some kind of leakage scheme alongside a suitable closure condition for the moment expansion of the radiation stresses (recent examples include [31][32][33] with, in particular [34] paying attention to the multi-frequency aspects), increasing realism by considering the angular dependency (as in [35,36]) or taking a full-blown Monte-Carlo approach (as in [37][38][39]). In essence, the problem is complex and extremely expensive computationally.…”

Section: Going Furthermentioning

confidence: 99%

Thermal aspects of neutron star mergers

2021

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In order to extract maximal information from neutron-star merger signals, both gravitational and electromagnetic, we need to ensure that our theoretical models/numerical simulations faithfully represent the extreme physics involved. This involves a range of issues, with the finite temperature effects regulating many of the relevant phenomena. As a step towards understanding these issues, we explore the conditions for β-equilibrium in neutron star matter for the densities and temperatures reached in a binary neutron star merger. Using the results from our out-of-equilibrium merger simulation, we consider how different notions of equilibrium may affect the merger dynamics, raising issues that arise when attempting to account for these conditions in future simulations. These issues are both computational and conceptual. We show that the effects lead to, in our case, a softening of the equation of state in some density regions, and to composition changes that affect processes that rely on deviation from equilibrium, such as bulk viscosity, both in terms of the magnitude and the equilibration timescales inherent to the relevant set of reactions. We also demonstrate that it is difficult to determine exactly which equilibrium conditions are relevant in which regions of the matter due to the dependence on neutrino absorption, further complicating the calculation of the reactions that work to restore the matter to equilibrium.

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Heavy Elements and Electromagnetic Transients from Neutron Star Mergers

Rosswog

Korobkin

2022

Annalen der Physik

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Compact binary mergers involving neutron stars can eject a fraction of their mass to space. Being extremely neutron rich, this material undergoes rapid neutron capture nucleosynthesis, and the resulting radioactivity powers fast, short‐lived electromagnetic transients known as kilonova or macronova. Such transients are exciting probes of the most extreme physical conditions and their observation signals the enrichment of the Universe with heavy elements. Here the current understanding of the mass ejection mechanisms, the properties of the ejecta, and the resulting radioactive transients are reviewed. The first well‐observed event in the aftermath of GW170817 delivered a wealth of insights, but much of today's picture of such events is still based on a patchwork of theoretical studies. Apart from summarizing the current understanding, questions where no consensus has been reached yet are also pointed out, and possible directions for the future research are sketched. In an appendix, a publicly available heating rate library based on the WinNet nuclear reaction network is described, and a simple fit formula to alleviate the implementation in hydrodynamic simulations is provided.

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νbhlight: Radiation GRMHD for Neutrino-driven Accretion Flows

Cited by 37 publications

References 59 publications

Realistic Kilonova Up Close

Realistic Kilonova Up Close

Thermal aspects of neutron star mergers

Heavy Elements and Electromagnetic Transients from Neutron Star Mergers

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