Neutron star merger remnants

Bernuzzi, Sebastiano

doi:10.1007/s10714-020-02752-5

Cited by 131 publications

(87 citation statements)

References 301 publications

(595 reference statements)

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“…The latter is crucial, as the neutrinos are thought to be necessary to trigger the supernova explosion. -The final problem setting-attracting a lot of interest at the present time (Baiotti and Rezzolla 2017;Bernuzzi 2020)-involves the inspiral and merger of binary neutron stars. Many of the challenges, regarding the physics, are the same as in the case of core-collapse simulations.…”

Section: The State Of the Artmentioning

confidence: 99%

Relativistic fluid dynamics: physics for many different scales

Andersson

Comer

2021

Living Rev Relativ

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The relativistic fluid is a highly successful model used to describe the dynamics of many-particle systems moving at high velocities and/or in strong gravity. It takes as input physics from microscopic scales and yields as output predictions of bulk, macroscopic motion. By inverting the process—e.g., drawing on astrophysical observations—an understanding of relativistic features can lead to insight into physics on the microscopic scale. Relativistic fluids have been used to model systems as “small” as colliding heavy ions in laboratory experiments, and as large as the Universe itself, with “intermediate” sized objects like neutron stars being considered along the way. The purpose of this review is to discuss the mathematical and theoretical physics underpinnings of the relativistic (multi-) fluid model. We focus on the variational principle approach championed by Brandon Carter and collaborators, in which a crucial element is to distinguish the momenta that are conjugate to the particle number density currents. This approach differs from the “standard” text-book derivation of the equations of motion from the divergence of the stress-energy tensor in that one explicitly obtains the relativistic Euler equation as an “integrability” condition on the relativistic vorticity. We discuss the conservation laws and the equations of motion in detail, and provide a number of (in our opinion) interesting and relevant applications of the general theory. The formalism provides a foundation for complex models, e.g., including electromagnetism, superfluidity and elasticity—all of which are relevant for state of the art neutron-star modelling.

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Section: The State Of the Artmentioning

confidence: 99%

Relativistic fluid dynamics: physics for many different scales

Andersson

Comer

2021

Living Rev Relativ

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“…Observations of the most massive NSs, such as J0740 þ 6620, have important implications beyond the EoS. They inform the NS mass distribution [57][58][59][60][61][62][63][64], the classification of the heaviest NS candidates observed with GWs [30], our understanding of the proposed mass gap between NSs and black holes [65,66], and the characteristics of NS merger remnants [67] that influence electromagnetic counterpart emission [68,69]. The properties of the high-density EoS are also connected to the properties at other density scales through correlations shaped by causality considerations [70,71].…”

Section: Introductionmentioning

confidence: 96%

Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter

et al. 2021

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X-ray pulse profile modeling of PSR J0740 þ 6620, the most massive known pulsar, with data from the NICER and XMM-Newton observatories recently led to a measurement of its radius. We investigate this measurement's implications for the neutron star equation of state (EoS), employing a nonparametric EoS model based on Gaussian processes and combining information from other x-ray, radio and gravitationalwave observations of neutron stars. Our analysis mildly disfavors EoSs that support a disconnected hybrid star branch in the mass-radius relation, a proxy for strong phase transitions, with a Bayes factor of 6.9. For such EoSs, the transition mass from the hadronic to the hybrid branch is constrained to lie outside ð1; 2Þ M ⊙ . We also find that the conformal sound-speed bound is violated inside neutron star cores, which implies that the core matter is strongly interacting. The squared sound speed reaches a maximum of 0.75 þ0.25 −0.24 c 2 at 3.60 þ2.25 −1.89 times nuclear saturation density at 90% credibility. Since all but the gravitational-wave observations prefer a relatively stiff EoS, PSR J0740 þ 6620's central density is only 3.57 þ1.3 −1.3 times nuclear saturation, limiting the density range probed by observations of cold, nonrotating neutron stars in β-equilibrium.

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“…The dynamics of the BNSM have frequently been modeled in the past to guide observation [187][188][189][190][191]. Modern general relativity (GR)-based hydrodynamic simulations have been reported [192,193] since the observation (for reviews, see [194,195]).…”

Section: Gravitational Waves 421 Observationmentioning

confidence: 99%

Nuclear Physics and Astrophysics Constraints on the High Density Matter Equation of State

Stone

2021

Universe

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(1) This review has been written in memory of Steven Moszkowski who unexpectedly passed away in December 2020. It has been inspired by our many years of discussions. Steven’s enthusiasm, drive and determination to understand atomic nuclei in simple terms of basic laws of physics was infectious. He sought the fundamental origin of nuclear forces in free space, and their saturation and modification in nuclear medium. His untimely departure left our job unfinished but his legacy lives on. (2) Focusing on the nuclear force acting in nuclear matter of astrophysical interest and its equation of state (EoS), we take several typical snapshots of evolution of the theory of nuclear forces. We start from original ideas in the 1930s moving through to its overwhelming diversity today. The development is supported by modern observational and terrestrial data and their inference in the multimessenger era, as well as by novel mathematical techniques and computer power. (3) We find that, despite the admirable effort both in theory and measurement, we are facing multiple models dependent on a large number of variable correlated parameters which cannot be constrained by data, which are not yet accurate, nor sensitive enough, to identify the theory closest to reality. The role of microphysics in the theories is severely limited or neglected, mostly deemed to be too difficult to tackle. (4) Taking the EoS of high-density matter as an example, we propose to develop models, based, as much as currently possible, on the microphysics of the nuclear force, with a minimal set of parameters, chosen under clear physical guidance. Still somewhat phenomenological, such models could pave the way to realistic predictions, not tracing the measurement, but leading it.

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Neutron star merger remnants

Cited by 131 publications

References 301 publications

Relativistic fluid dynamics: physics for many different scales

Relativistic fluid dynamics: physics for many different scales

Impact of the PSR J0740+6620 radius constraint on the properties of high-density matter

Nuclear Physics and Astrophysics Constraints on the High Density Matter Equation of State

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