Supermassive neutron stars rule out twin stars

Christian, Jan-Erik; Schaffner-Bielich, J.

doi:10.1103/physrevd.103.063042

Cited by 33 publications

(29 citation statements)

References 65 publications

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“…On the other hand, the possibility for GW190814's secondary as a neutron star can be accomplished by: (1) choosing/constructing stiff EOSs having a maximum mass larger than 2.5 M [76,[141][142][143][144][145][146][147][148][149][150]; (2) considering the effects of fast rotations, which can increase the maximum mass by about 20% when a star rotates at the Kepler frequency (the maximum frequency at which the gravitational attraction is still sufficient to keep matter bound to the pulsar surface) [42,43,139,140,145,[151][152][153][154][155][156][157] ; (3) considering other effects/models that can modify the maximum mass of a neutron star, such as the magnetic field [147], twin star [158], two families of compact stars [142], finite temperature [153], antikaon condensation [159], net electric charge [144], etc.…”

Section: Is Gw190814's Secondary a Superfast And Supermassive Neutron Star Or Something Else?mentioning

confidence: 99%

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Cai²,

Wang

et al. 2021

Universe

147

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The density dependence of nuclear symmetry energy is among the most uncertain parts of the Equation of State (EOS) of dense neutron-rich nuclear matter. It is currently poorly known especially at suprasaturation densities partially because of our poor knowledge about isovector nuclear interactions at short distances. Because of its broad impacts on many interesting issues, pinning down the density dependence of nuclear symmetry energy has been a longstanding and shared goal of both astrophysics and nuclear physics. New observational data of neutron stars including their masses, radii, and tidal deformations since GW170817 have helped improve our knowledge about nuclear symmetry energy, especially at high densities. Based on various model analyses of these new data by many people in the nuclear astrophysics community, while our brief review might be incomplete and biased unintentionally, we learned in particular the following: (1) The slope parameter L of nuclear symmetry energy at saturation density ρ0 of nuclear matter from 24 new analyses of neutron star observables was about L≈57.7±19 MeV at a 68% confidence level, consistent with its fiducial value from surveys of over 50 earlier analyses of both terrestrial and astrophysical data within error bars. (2) The curvature Ksym of nuclear symmetry energy at ρ0 from 16 new analyses of neutron star observables was about Ksym≈−107±88 MeV at a 68% confidence level, in very good agreement with the systematics of earlier analyses. (3) The magnitude of nuclear symmetry energy at 2ρ0, i.e., Esym(2ρ0)≈51±13 MeV at a 68% confidence level, was extracted from nine new analyses of neutron star observables, consistent with the results from earlier analyses of heavy-ion reactions and the latest predictions of the state-of-the-art nuclear many-body theories. (4) While the available data from canonical neutron stars did not provide tight constraints on nuclear symmetry energy at densities above about 2ρ0, the lower radius boundary R2.01=12.2 km from NICER’s very recent observation of PSR J0740+6620 of mass 2.08±0.07M⊙ and radius R=12.2–16.3 km at a 68% confidence level set a tight lower limit for nuclear symmetry energy at densities above 2ρ0. (5) Bayesian inferences of nuclear symmetry energy using models encapsulating a first-order hadron–quark phase transition from observables of canonical neutron stars indicated that the phase transition shifted appreciably both L and Ksym to higher values, but with larger uncertainties compared to analyses assuming no such phase transition. (6) The high-density behavior of nuclear symmetry energy significantly affected the minimum frequency necessary to rotationally support GW190814’s secondary component of mass (2.50–2.67) M⊙ as the fastest and most massive pulsar discovered so far. Overall, thanks to the hard work of many people in the astrophysics and nuclear physics community, new data of neutron star observations since the discovery of GW170817 have significantly enriched our knowledge about the symmetry energy of dense neutron-rich nuclear matter.

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Section: Is Gw190814's Secondary a Superfast And Supermassive Neutron Star Or Something Else?mentioning

confidence: 99%

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Cai²,

Wang

et al. 2021

Universe

147

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“…in Refs. [11,12,20,21], twin star configurations arise when a sharp phase transition of the QCD matter occurs. In our analysis, we will assume that hadronic matter (HM) is described by the stiffest EoS of Hebeler et al [39] which is obtained from effective chiral field theory, used between baryon densities of n B ∈ [0.6, 1.1]n 0 , and being supplemented by the BPS EoS [40] for the outer crust with n B < 0.6n 0 .…”

Section: Equations Of Statementioning

confidence: 99%

“…If such a phase transition is sharp, a third family of compact stars can be present in the mass-radius diagram, with smaller radii but similar masses to those predicted for the disconnected second family branch [2][3][4][5][6][7][8][9]. The description of these twin star configurations has been a theme of debate in recent years [10][11][12][13][14][15][16][17][18][19][20][21], mainly motivated by the perspective that future X-ray astronomy will be able to measure the masses and radii of compact stars with a high precision. The studies performed, e.g., in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…The studies performed, e.g., in Refs. [11,12,20,21] indicate that the properties of the twin stars is strongly sensitive to the treatment of the phase transition in ultra dense matter. As a a e-mail: barros@ufpel.edu.br (corresponding author) consequence, a future discovery of twin stars will be important to improve our understanding about the equation of state (EoS) of compact objects.…”

Section: Introductionmentioning

confidence: 99%

“…2 Very recently, the analysis of these supermassive compact stars has been considered to constrain twin stars, with the results derived in Ref. [20] pointing out that a mass constraint of 2.5 M ruled out all twin star solutions, while Ref. [21] concluded that these ultra heavy NSs can be in a twin-mass configuration but the two stable branches must be connected.…”

Section: Introductionmentioning

confidence: 99%

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Electrically charged supermassive twin stars

2022

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By assuming that ultra dense hybrid neutron stars are endowed with a distribution of electric charge, we study the corresponding twin star solutions and their properties resulting from a sharp first order transition from confined hadronic to a deconfined quark phase. Two distinct quark matter equations of state with increasing stiffness are considered and the values for the maximum gravitational masses of the hadronic and hybrid twin configurations are obtained for different values of the total electric charge. Interestingly, our calculations indicate that sharp transitions make charged twin hybrid stars more massive than their neutral counterparts, and that the $${2}\,{\hbox {M}_{\odot }}$$ 2 M ⊙ constraint from PSR J0740+6620 is surpassed for standard values of electric charge and can be considered stable only satisfying $$\partial M/\partial \epsilon _0 > 0$$ ∂ M / ∂ ϵ 0 > 0 . In particular, our charged stellar models reach masses even higher than the unknown compact object measured in the GW190814 event.

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Studying the onset of deconfinement with multi‐messenger astronomy of neutron stars

Blaschke

Cierniak

2021

Astron Nachr

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With the first multi‐messenger observation of a binary neutron star merger (GW170817), new constraints became available for masses and radii of neutron stars. We introduce a class of hybrid EoS that fulfills all these constraints and predicts a region in the mass‐radius diagram that could be populated only by hybrid neutron stars with quark matter cores. A confirmation of this conjecture would be provided when the NICER radius measurement for the high‐mass pulsar PSR J0740 + 6620 yields a radius significantly less than 11 km. Would this radius measurement yield a result in excess of 12 km, this would allow for both, a purely hadronic and a hybrid nature of this star. In the latter case, the maximum mass could reach 2.6 M⊙ so that the lighter object in the asymmetric binary merger GW190814 could have been a hybrid star. We demonstrate that this high mass can be compatible with an early onset of deconfinement for stars with masses below 1 M⊙ and the occurrence of low‐mass twin stars. In such a case, the remnant of GW170817 could be a long‐lived hypermassive pulsar.

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Supermassive neutron stars rule out twin stars

Cited by 33 publications

References 65 publications

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817

Electrically charged supermassive twin stars

Studying the onset of deconfinement with multi‐messenger astronomy of neutron stars

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