How strange are compact star interiors?

Blaschke, D.; Klähn, T.; Łastowiecki, R.; Sandin, Fredrik

doi:10.1088/0954-3899/37/9/094063

Cited by 37 publications

(41 citation statements)

References 40 publications

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“…In spite of this softening, the existence of 2M pulsars does not exclude quark cores in NS, but imposes rather tight constraints on the EOS with N-Q transition [100,101]. Two subsequent phase transitions through the intermediate quark phase energetically preferred in a rather narrow range of densities were also considered [102][103][104][105].…”

Section: Hybrid Starsmentioning

confidence: 99%

Rotating neutron stars with exotic cores: masses, radii, stability

Haensel¹,

Bejger²,

Fortin³

et al. 2016

Eur. Phys. J. A

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Abstract.A set of theoretical mass-radius relations for rigidly rotating neutron stars with exotic cores, obtained in various theories of dense matter, is reviewed. Two basic observational constraints are used: the largest measured rotation frequency (716 Hz) and the maximum measured mass (2M ). The present status of measuring the radii of neutron stars is described. The theory of rigidly rotating stars in general relativity is reviewed and limitations of the slow rotation approximation are pointed out. Mass-radius relations for rotating neutron stars with hyperon and quark cores are illustrated using several models. Problems related to the non-uniqueness of the crust-core matching are mentioned. Limits on rigid rotation resulting from the mass-shedding instability and the instability with respect to the axisymmetric perturbations are summarized. The problem of instabilities and of the back-bending phenomenon are discussed in detail. Metastability and instability of a neutron star core in the case of a first-order phase transition, both between pure phases, and into a mixed-phase state, are reviewed. The case of two disjoint families (branches) of rotating neutron stars is discussed and generic features of neutron-star families and of core-quakes triggered by the instabilities are considered.

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Section: Hybrid Starsmentioning

confidence: 99%

Rotating neutron stars with exotic cores: masses, radii, stability

Haensel¹,

Bejger²,

Fortin³

et al. 2016

Eur. Phys. J. A

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“…The description of normal quark matter phases with two and three flavours is straightforward and shows the qualitative difference to bag models of quark matter already: light and strange quark flavours appear sequentially [29] due to the fact that different chemical potentials are required to reach the dynamically generated light and strange quark masses, so that strange quarks appear in cold quark matter only at high densities, eventually too high for CS interiors [30,31,32].…”

Section: Advanced Njl Model For High-density Quark Mattermentioning

confidence: 98%

“…It has been pioneered in 2005 independently by two groups, Blaschke et al [33] and Ruester et al [34] who showed that all previous results for superconducting quark matter in CS interiors (which worked with fixed strange quark mass) were flawed since they could not reveal the feature of sequential deconfinement of strangeness. This code has been developed further to include vector meanfields which provide a stiffening of high-density quark matter and allow to fulfil high-mass pulsar constraints [30,31,32]. It has been further developed to include the coupling to the Polyakov loop (PNJL model) as an implementation of confining effects at finite temperatures to facilitate applications to supernova collapse simulations [35].…”

Section: Advanced Njl Model For High-density Quark Mattermentioning

confidence: 99%

High-mass twins & resolution of the reconfinement, masquerade and hyperon puzzles of compact star interiors

Blaschke

Alvarez-Castillo

2016

AIP Conference Proceedings

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Abstract. We aim at contributing to the resolution of three of the fundamental puzzles related to the still unsolved problem of the structure of the dense core of compact stars (CS): (i) the hyperon puzzle: how to reconcile pulsar masses of 2 M with the hyperon softening of the equation of state (EoS); (ii) the masquerade problem: modern EoS for cold, high density hadronic and quark matter are almost identical; and (iii) the reconfinement puzzle: what to do when after a deconfinement transition the hadronic EoS becomes favorable again? We show that taking into account the compositeness of baryons (by excluded volume and/or quark Pauli blocking) on the hadronic side and confining and stiffening effects on the quark matter side results in an early phase transition to quark matter with sufficient stiffening at high densities which removes all three present-day puzzles of CS interiors. Moreover, in this new class of EoS for hybrid CS falls the interesting case of a strong first order phase transition which results in the observable high mass twin star phenomenon, an astrophysical observation of a critical endpoint in the QCD phase diagram.

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“…A stiff superconducting quark core instead of hyperon core (such stars are called "hybrid stars" because they have baryon (B) and quark-matter (Q) components) could allow for M max > 2 M ⊙ (e.g., [16,17,18,14,19]). However, necessary conditions on the baryon -quark-matter phase transition (B −→ Q), leading to EOS.BQ respecting M max > 2 M ⊙ , are very strong.…”

Section: Eos and Qcdmentioning

confidence: 99%

Maximum pulsar mass, equation of state and structure of neutron-star cores

Haensel

Zdunik

2016

J. Phys.: Conf. Ser.

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Abstract.The structure of neutron stars is determined by the equation of state of dense matter in their interiors. Brief review of the equation of state from neutron star surface to its center is presented. Recent discovery of two two-solar-mass pulsars puts interesting constraints on the poorly known equation of state of neutron-star cores for densities greater than normal nuclear matter density. Namely, this equation of state has to be stiff enough to yield maximum allowable mass of neutron stars greater than two solar masses. There are many models of neutron stars cores involving exclusively nucleons that satisfy this constraint. However, for neutron-star models based on recent realistic baryon interaction, and allowing for the presence of hyperons, the hyperon softening of the equation of state yields maximum masses significantly lower than two solar masses. Proposed ways out from this "hyperon puzzle" are presented. They require a very fine tuning of parameters of dense hadronic matter and quark matter models. Consequences for the mass-radius relation for neutron stars are illustrated. A summary of the present situation and possible perspectives/challenges, as well as possible observational tests, are given. IntroductionThe equation of state (EOS) of neutron stars (NS) is one of their mysteries. For astrophysically interesting masses, M > M ⊙ , and for NS which are older than a year, the effects of temperature, magnetic field, and of rotation, on the NS structure are small [1], and will be neglected here. Then, the structure of NS, and in particular their maximum allowable mass, M max , is determined by the EOS [1].To construct models of NS, from the surface (or rather from an atmosphere, which is however typically only a few cm thick) to the star's center, we need the EOS for density from a fraction of g cm −3 up to some 5 × 10 15 g cm −3 . A general overview of theoretical EOSs for NS, from the surface to the center, is given in Sect. 2.As we stress in Sect. 2, at density larger than 10 6 g cm −3 , matter in NS is strongly degenerate, and therefore pressure becomes a function of the density only, P = P (ρ). Up to the normal nuclear density ρ 0 = 2.7 × 10 14 g cm −3 , corresponding to the baryon (number) density n 0 = 0.16 fm −3 , the EOS is rather well established [2]. However, for ρ > ρ 0 the uncertainty in the EOS increases rapidly with increasing ρ. This uncertainty is reflected in the uncertainty in the theoretical prediction for M max , which is the functional of P (ρ):

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How strange are compact star interiors?

Cited by 37 publications

References 40 publications

Rotating neutron stars with exotic cores: masses, radii, stability

Rotating neutron stars with exotic cores: masses, radii, stability

High-mass twins & resolution of the reconfinement, masquerade and hyperon puzzles of compact star interiors

Maximum pulsar mass, equation of state and structure of neutron-star cores

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