Special point on the mass-radius diagram of hybrid stars

Yudin, A. V.; Razinkova, T. L.; Nadyozhin, D. K.; Dolgov, A. D.

doi:10.1134/s1063773714040069

Cited by 32 publications

(42 citation statements)

References 14 publications

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“…As the transition density rises the radius of a 1.4 M star decreases at first, but then increases again. This is related to the previously noted fact [30] that when one fixes the speed of sound of quark matter and increases the bag constant (which increases p trans /ε trans and also varies ∆ ε/ε trans in a correlated way) the resultant family of mass-radius curves all pass through the same small region in the M-R plane: the M(R) curves "rotate" counter-clockwise around this hub (see Fig. 2 of Ref.…”

Section: Radius Of a 14 M Starmentioning

confidence: 58%

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Characteristics of hybrid compact stars with a sharp hadron-quark interface

Alford

Han

2016

Eur. Phys. J. A

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We describe two aspects of the physics of hybrid stars that have a sharp interface between a core of quark matter and a mantle of nuclear matter. Firstly, we analyze the mass-radius relation. We describe a generic "Constant-Speed-of-Sound" (CSS) parameterization of the quark matter equation of state (EoS), in which the speed of sound is independent of density. In terms of the three parameters of the CSS EoS we obtain the phase diagram of possible forms of the hybrid star mass-radius relation, and we show how observational constraints on the maximum mass and typical radius of neutron stars can be expressed as constraints on the CSS parameters. Secondly, we propose a mechanism for the damping of density oscillations, including r-modes, in hybrid stars with a sharp interface. The dissipation arises from the periodic conversion between quark matter and nuclear matter induced by the pressure oscillations in the star. We find the damping grows nonlinearly with the amplitude of the oscillation and is powerful enough to saturate an r-mode at very low saturation amplitude, of order 10 −10 , which is compatible with currently-available observations of neutron star spin frequencies and temperatures.PACS. 25.75.Nq Quark deconfinement, quark-gluon plasma production, and phase transitions -26.60.-c Nuclear matter aspects of neutron stars -97.60.Jd Neutron stars arXiv:1508.01261v2 [nucl-th]

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Section: Radius Of a 14 M Starmentioning

confidence: 58%

“…2 of Ref. [30]). In our case we are varying p trans /ε trans at fixed ∆ ε/ε trans , so the hub itself also moves.…”

Section: Radius Of a 14 M Starmentioning

confidence: 88%

Characteristics of hybrid compact stars with a sharp hadron-quark interface

Alford

Han

2016

Eur. Phys. J. A

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“…As the transition density rises the radius of a 1.4 M star decreases at first, but then increases again. This is related to the previously noted fact [27] that when one fixes the speed of sound of quark matter and increases the bag constant (which increases p trans /ε trans and also varies ∆ε/ε trans in a correlated way) the resultant family of mass-radius curves all pass through the same small region in the M-R plane: the M(R) curves "rotate" counterclockwise around this hub (see Fig. 2 of Ref.…”

Section: Typical Radius Of Hybrid Starsmentioning

confidence: 60%

“…2 of Ref. [27]). In our case we are varying p trans /ε trans at fixed ∆ε/ε trans , so the hub itself also moves.…”

Section: Typical Radius Of Hybrid Starsmentioning

confidence: 88%

Constraining and applying a generic high-density equation of state

et al. 2015

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We discuss the "constant speed of sound" (CSS) parameterization of the equation of state of high density matter and its application to the Field Correlator Method (FCM) model of quark matter. We show how observational constraints on the maximum mass and typical radius of neutron stars are expressed as constraints on the CSS parameters. We find that the observation of a 2 M star already severely constrains the CSS parameters, and is particularly difficult to accommodate if the squared speed of sound in the high density phase is assumed to be around 1/3 or less.We show that the FCM equation of state can be accurately represented by the CSS parameterization, which assumes a sharp transition to a high-density phase with density-independent speed of sound. We display the mapping between the FCM and CSS parameters, and see that FCM only allows equations of state in a restricted subspace of the CSS parameters.

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“…[29]). A recent study [30] has found, that EoS from the class of CSS models share the property that all M-R curves, regardless of the hybrid star onset density, must cross a small region in the M-R diagram, the SP. We would like to extend this study to a wider range of EoS with additional microscopic features, such as vector repulsion, and investigate the possibility that the existence of a SP is a universal property of hybrid neutron star models.…”

Section: Introductionmentioning

confidence: 99%

The special point on the hybrid star mass–radius diagram and its multi–messenger implications

Cierniak

Blaschke

2020

Eur. Phys. J. Spec. Top.

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We show the existence and investigate the location of the special point (SP) in which hybrid neutron star mass-radius (M-R) curves have to cross each other when they belong to a class of hybrid equation of state (EoS) constructed with generic constant–speed–of–sound (CSS) quark matter models for which the onset deconfinement is varied. We demonstrate that for a three-parameter CSS model the position of the SP in the M-R diagram is largely independent of the choice of the hadronic EoS, but in dependence on the stiffness of the quark matter EoS it spans a region that we identify. We find that the difference between the maximum mass and the SP mass depends on the mass at the onset of deconfinement so that an upper limit of 0.19 M⊙ for this difference is obtained from which a lower limit on the radius of hybrid stars is deduced. Together with a lower limit on the radius of hadronic stars, derived from a class of reasonably soft hadronic EoS including hyperons, we identify a region in the M-R diagram which can be occupied only by hybrid stars. Accordingly, we suggest that a NICER radius measurement on the massive pulsar PSR J0740 + 6620 in the range of 8.6-11.9 km would indicate that this pulsar is a hybrid neutron star with deconfined quark matter in the inner core.

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Special point on the mass-radius diagram of hybrid stars

Abstract: An analytical study that explains the existence of a very small region on the mass-radius

Cited by 32 publications

References 14 publications

Characteristics of hybrid compact stars with a sharp hadron-quark interface

Characteristics of hybrid compact stars with a sharp hadron-quark interface

Constraining and applying a generic high-density equation of state

The special point on the hybrid star mass–radius diagram and its multi–messenger implications

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