Extreme matter meets extreme gravity: Ultraheavy neutron stars with phase transitions

Tan, Hung; Dore, Travis; Dexheimer, V.; Noronha-Hostler, Jacquelyn; Yunes, Nicolás

doi:10.1103/physrevd.105.023018

Cited by 56 publications

(31 citation statements)

References 178 publications

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“…The orange line marks again the outer envelope spanned by sub-conformal EOSs, whose maximum mass is M ≈ 2.1 M , also seen in [46,61]. This behaviour confirms on rather general grounds the tension between c 2 s,max < 1/3 and the observation of stars with M > ∼ 2 M , already been pointed out, for example, in [8,[62][63][64].…”

supporting

confidence: 83%

On the Sound Speed in Neutron Stars

Altiparmak¹,

Ecker²,

Rezzolla³

2022

Preprint

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Determining the sound speed cs in compact stars is an important open question with numerous implications on the behaviour of matter at large densities and hence on gravitational-wave emission from neutron stars. To this scope, we construct more than 10 7 equations of state (EOSs) with continuous sound speed and build more than 10 8 nonrotating stellar models consistent not only with nuclear theory and perturbative QCD, but also with astronomical observations. In this way, we find that EOSs with sub-conformal sound speeds, i.e., with c 2 s < 1/3 within the stars, are possible in principle but very unlikely in practice, being only 0.03% of our sample. Hence, it is natural to expect that c 2 s > 1/3 somewhere in the stellar interior. Using our large sample, we obtain estimates at 95% credibility of neutron-star radii for representative stars with 1.4 and 2.0 solar masses, R1.4 = 12.42 +0.52 −0.99 km, R2.0 = 12.12 +1.11 −1.23 km, and for the binary tidal deformability of the GW170817 event, Λ1.186 = 485 +225 −211 . Interestingly, our lower-bounds on the radii are in very good agreement with the prediction derived from very different arguments, namely, the threshold mass. Finally, we provide simple analytic expressions to determine the minimum and maximum values of Λ as a function of the chirp mass.

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supporting

confidence: 83%

On the Sound Speed in Neutron Stars

Altiparmak¹,

Ecker²,

Rezzolla³

2022

Preprint

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“…For example, Refs. [56,57] study EoS with complex speedof-sound phenomenology, while Refs. [51,[58][59][60][61][62] consider strong first-order phase transitions that result in a discontinuity in the speed of sound and multiple stable branches.…”

Section: Discussionmentioning

confidence: 99%

Implicit correlations within phenomenological parametric models of the neutron star equation of state

2022

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The rapid increase in the number and precision of astrophysical probes of neutron stars in recent years allows for the inference of their equation of state. Observations target different macroscopic properties of neutron stars which vary from star to star, such as mass and radius, but the equation of state allows for a common description of all neutron stars. To connect these observations and infer the properties of dense matter and neutron stars simultaneously, models for the equation of state are introduced. Parametric models rely on carefully engineered functional forms that reproduce a large array of realistic equations of state. Such models benefit from their simplicity but are limited because any finite-parameter model cannot accurately approximate all possible equations of state. Nonparametric methods overcome this by increasing model freedom at the cost of increased complexity. In this study, we compare common parametric and nonparametric models, quantify the limitations of the former, and study the impact of modeling on our current understanding of high-density physics. We show that parametric models impose strongly model-dependent, and sometimes opaque, correlations between density scales. Such interdensity correlations result in tighter constraints that are unsupported by data and can lead to biased inference of the equation of state and of individual neutron star properties.

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“…Finally, in the neutron star case, the maximum sound velocity can reach ∼ 0.8c [75] if one takes the observational constraints into consideration (mainly the ∼ 2 M TOV-mass constraint [76][77][78][79][80]). Lately there are various studies [81][82][83][84][85][86][87][88][89][90] regarding its complicated density-dependence at the density region of several times of the saturation density ρ 0 . We mention here that the high peak value of the sound velocity in neutron star matter [91], compared to that in pure quark matter, can naturally be understood as a correspondence of low surface density that has been demonstrated previously in Fig.…”

Section: B Stability Of Self-bound Quark Matter and The Equation Of S...mentioning

confidence: 99%

Interacting $ud$ and $uds$ quark matter at finite densities and quark stars

Yuan,

Li,

Miao

et al. 2022

Preprint

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The stability and equation of state of quark matter are studied within both two-flavor and (2+1)-flavor Nambu-Jona-Lasinio (NJL) models including the vector interactions. With a free parameter α, the Lagrangian is constructed by two parts, the original NJL Lagrangian and the Fierz transformation of it, as L = (1 − α)LNJL + αLFierz. We find that there is a possibility for both ud nonstrange and uds strange matter being absolute stable, depending on the interplay of the confinement with quark vector interaction and the exchange interaction channels. The calculated quark star properties can reconcile with the recently measured masses and radii of PSR J0030+0451 and PSR J0740+6620, as well as the tidal deformability of GW170817. Furthermore, the more strongly-interacting quark matter in the nonstrange stars allows a stiffer equation of state and consequently a higher maximum mass (∼ 2.7 M ) than the strange ones (∼ 2.1 M ). The sound velocities in strange and nonstrange quark star matter are briefly discussed compared to those of neutron star matter.

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Extreme matter meets extreme gravity: Ultraheavy neutron stars with phase transitions

Cited by 56 publications

References 178 publications

On the Sound Speed in Neutron Stars

On the Sound Speed in Neutron Stars

Implicit correlations within phenomenological parametric models of the neutron star equation of state

Interacting $ud$ and $uds$ quark matter at finite densities and quark stars

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