Confronting gravitational-wave observations with modern nuclear physics constraints

Tews, Ingo; Margueron, J.; Reddy, Sanjay

doi:10.1140/epja/i2019-12774-6

Cited by 121 publications

(97 citation statements)

References 83 publications

(172 reference statements)

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“…We also find a preference for EOSs that support multiple stable branches in their M -R and M -Λ relations with our agnostic prior when comparing results using GW and pulsar data against pulsar data alone. While far from conclusive, we note that if the EOS supports multiple stable branches, there is a noticeable preference for dramatic softening around ρ nuc followed by stiffening around 2ρ nuc , consistent with a phase transition and predictions for where chiral effective field theory may break down [25][26][27][28]. However, the exact onset density, pressure, and latent energy remain uncertain by at least a factor of a few.…”

Section: Discussionsupporting

confidence: 63%

“…Remarkably, with the agnostic prior, we find that GW170817 modestly favors EOSs that support a disconnected hybrid star branch, one signature of a strong first-order phase transition. Among such EOSs, GW170817 suggests a possible phase transition with on-set density between ρ nuc and 2ρ nuc , in agreement with chiral effective field theory predictions for the breakdown of perturbations off of asymmetric nuclear matter [25][26][27][28]. Our nonparametric inference attaches no a priori significance to these particular densities; the preference observed a posteriori is entirely driven by data from GW170817 and M max constraints from observations of massive pulsars.…”

Section: Introductionsupporting

confidence: 65%

“…Similarly, including better constraints on the theoretical uncertainty at low densities by matching to chiral effective field theory with theoretical uncertainties from truncating series expansions [25][26][27][28] should further constrain our priors. We note, though, that GW170817 produces posterior processes that already tend to follow the prior relatively closely below ρ nuc (see Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…While we stress that the statistical evidence in favor of EOSs that support multiple stable branches in the M -R relation is weak, GW170817's preference for soft EOSs, in conjunction with the existence of a 2 M pulsar, could be interpreted as evidence for a strong phase transition between ρ nuc and 2ρ nuc , although the precise onset density, pressure, and latent energy associated with such a phase transition are still largely uncertain. Nonetheless, some theoretical studies of chiral effective field theory suggest that the purely hadronic model for the EOS will break down in this density range due to phase transitions [25][26][27][28]. This coincidence is intriguing, especially since none of our input candidate EOSs are computed FIG.…”

Section: Implications For Neutron-star Compositionmentioning

confidence: 98%

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Nonparametric inference of neutron star composition, equation of state, and maximum mass with GW170817

2020

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The detection of GW170817 in gravitational waves provides unprecedented constraints on the equation of state (EOS) of the ultra-dense matter within the cores of neutron stars (NSs). We extend the nonparametric analysis first introduced in Landry & Essick (2019), and confirm that GW170817 favors soft EOSs. We infer macroscopic observables for a canonical 1.4 M NS, including the tidal deformability Λ1.4 = 211 +312 −137 (491 +216 −181 ) and radius R1.4 = 10.86 +2.04 −1.42 (12.51 +1.00 −0.88 ) km, as well as the maximum mass for nonrotating NSs, Mmax = 2.064 +0.260 −0.134 (2.017 +0.238 −0.087 ) M , with nonparametric priors loosely (tightly) constrained to resemble candidate EOSs from the literature. Furthermore, we find weak evidence that GW170817 involved at least one NS based on gravitational-wave data alone (B NS BBH = 3.3 ± 1.4), consistent with the observation of electromagnetic counterparts. We also investigate GW170817's implications for the maximum spin frequency of millisecond pulsars, and find that the fastest known pulsar is spinning at more than 50% of its breakup frequency at 90% confidence. We additionally find modest evidence in favor of quark matter within NSs, and GW170817 favors the presence of at least one disconnected hybrid star branch in the mass-radius relation over a single stable branch by a factor of 2. Assuming there are multiple stable branches, we find a suggestive posterior preference for a sharp softening around nuclear density followed by stiffening around twice nuclear density, consistent with a strong first-order phase transition. While the statistical evidence in favor of new physics within NS cores remains tenuous with GW170817 alone, these tantalizing hints reemphasize the promise of gravitational waves for constraining the supranuclear EOS.

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Section: Discussionsupporting

confidence: 63%

Section: Introductionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Section: Implications For Neutron-star Compositionmentioning

confidence: 98%

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Nonparametric inference of neutron star composition, equation of state, and maximum mass with GW170817

2020

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“…Such a relation has also been derived in Ref. [77] from a very general approach based on a parameterization of the speed of sound. The relation Λ 1.4 × R 1.4 is important, in particular, since there is a range for Λ 1.4 provided by the LVC, namely, Λ 1.4 = 190 +390 −120 .…”

Section: Still Regarding the Values Shown Inmentioning

confidence: 88%

GW170817 constraints analyzed with Gogny forces and momentum-dependent interactions

et al. 2020

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A set of equations of state obtained from finite-range Gogny forces and momentum-dependent interactions is used to investigate the recent observation of gravitational waves from the binary neutron star merger GW170817 event. For this set of interactions, we have calculated the neutron star tidal deformabilities (related to the second Love number), the mass-radius diagram, and the moment of inertia (I). The I-Love relation has been verified. We also have found strong correlations among the tidal deformability of the canonical neutron star, its radius, and the derivatives of the nuclear symmetry energy at the saturation density. Most of the obtained results are located within the constraints of the tidal deformabilities extracted from the GW170817 detection.

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Neutron-star tidal deformability and equation-of-state constraints

2020

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Despite their long history and astrophysical importance, some of the key properties of neutron stars are still uncertain. The extreme conditions encountered in their interiors, involving matter of uncertain composition at extreme density and isospin asymmetry, uniquely determine the stars' macroscopic properties within General Relativity. Astrophysical constraints on those macroscopic properties, such as neutron star masses and radii, have long been used to understand the microscopic properties of the matter that forms them. In this article we discuss another astrophysically observable macroscopic property of neutron stars that can be used to study their interiors: their tidal deformation. Neutron stars, much like any other extended object with structure, are tidally deformed when under the influence of an external tidal field. In the context of coalescences of neutron stars observed through their gravitational wave emission, this deformation, quantified through a parameter termed the tidal deformability, can be measured. We discuss the role of the tidal deformability in observations of coalescing neutron stars with gravitational waves and how it can be used to probe the internal structure of Nature's most compact matter objects. Perhaps inevitably, a large portion of the discussion will be dictated by GW170817, the most informative confirmed detection of a binary neutron star coalescence with gravitational waves as of the time of writing.

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Confronting gravitational-wave observations with modern nuclear physics constraints

Cited by 121 publications

References 83 publications

Nonparametric inference of neutron star composition, equation of state, and maximum mass with GW170817

Nonparametric inference of neutron star composition, equation of state, and maximum mass with GW170817

GW170817 constraints analyzed with Gogny forces and momentum-dependent interactions

Neutron-star tidal deformability and equation-of-state constraints

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