The role of pressure anisotropy on the maximum mass of cold compact stars

AbstractWe study the thermodynamic properties of asymmetric quark matter, large mass quark stars (QSs), and proto-quark stars (PQSs) within the quasiparticle model. Considering the effects of temperature within quasiparticle model can significantly influence the EOS and the entropy of strange quark matter (SQM), quark fractions in SQM, as well as the tidal deformability and the maximum mass of PQSs along the star evolution line. Our results indicate that the recent discovered heavy compact stars PSR J0348+0432, MSR J0740+6620, PSR J2215+5135, and especially the GW190814’s secondary component $$m_2$$ m 2 can be well described as QSs within the quasiparticle model. The tidal deformability for the QSs describing the heavy compact stars is extremely large, which can not well describe GW170817 as QSs, and the effects of the temperature in the heating process along the star evolution will further increase the tidal deformability and the maximum mass of PQSs.

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The possibility of twin star solutions in a model based on lattice QCD thermodynamics

The European Physical Journal C ◽

10.1140/epjc/s10052-020-08779-x ◽

2021 ◽

Vol 81 (1) ◽

Author(s):

P. Jakobus ◽

A. Motornenko ◽

R. O. Gomes ◽

J. Steinheimer ◽

H. Stoecker

Keyword(s):

Neutron Stars ◽

Lattice Qcd ◽

Model Equation ◽

Compact Stars ◽

Model Parameters ◽

Bag Model ◽

First Order ◽

Stellar Masses ◽

First Order Phase

AbstractThe properties of compact stars and in particular the existence of twin star solutions are investigated within an effective model that is constrained by lattice QCD thermodynamics. The model is modified at large baryon densities to incorporate a large variety of scenarios of first order phase transitions to a phase of deconfined quarks. This is achieved by matching two different variants of the bag model equation of state, in order to estimate the role of the Bag model parameters on the appearance of a second family of neutron stars. The produced sequences of neutron stars are compared with modern constrains on stellar masses, radii, and tidal deformability from astrophysical observations and gravitational wave analyses. It is found that those scenarios in our analysis, in which a third family of stars appeared due to the deconfinement transition, are disfavored from astrophysical constraints.

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Temperature oscillations of a gas moving close to circular geodesic in Reissner–Nordström spacetime

International Journal of Modern Physics D ◽

10.1142/s0218271819500597 ◽

2019 ◽

Vol 28 (04) ◽

pp. 1950059 ◽

Cited By ~ 1

Author(s):

Leandro Cesar Mehret ◽

Gilberto Medeiros Kremer

Keyword(s):

Black Holes ◽

Electric Charge ◽

Periodic Oscillation ◽

Compact Stars ◽

Quark Stars ◽

Temperature Oscillations ◽

Inverse Effect ◽

Low Mass ◽

X Ray Binaries

The objective of this work is to analyze the temperature oscillations that occur in a gas in a circular motion under the action of a Reissner–Nordström gravitational field, verifying the effect of the charge term of the metric on the oscillations. The expression for temperature oscillations follows from Tolman’s law written in Fermi normal coordinates for a comoving observer. The motion of the gas is close to geodesic so the equation of geodesic deviation was used to obtain the expression for temperature oscillations. Then these oscillations are calculated for some compact stars, quark stars, black holes and white dwarfs, using values of electric charge and mass from models found in the literature. Comparing the various models analyzed, it is possible to verify that the role of the charge is the opposite of the mass. While the increase of the mass produces a reduction in the frequencies, amplitude and, in the ratio between the frequencies, the increase of the electric charge produces the inverse effect. In addition, it is shown that if the electric charge is proportional to the mass, the ratio between the frequencies does not depend on the mass, but only on the proportionality factor between charge and mass. The ratios between the frequencies for all the models analyzed (except for supermassive black holes in the extreme limit situations) are close to the [Formula: see text] ratio for twin peak quasi-periodic oscillation (QPO) frequencies, observed in many galactic black holes and neutron star sources in low-mass X-ray binaries.

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Dark matter with chiral symmetry admixed hadronic matter in compact stars

Chinese Physics C ◽

10.1088/1674-1137/ac3d28 ◽

2021 ◽

Author(s):

SiNa Wei ◽

Zhaoqing Feng

Keyword(s):

Dark Matter ◽

Energy Density ◽

Chiral Symmetry ◽

Density Ratio ◽

Compact Stars ◽

Hadronic Matter ◽

Meson Exchange ◽

Maximum Mass ◽

Central Energy ◽

Two Fluid

Abstract With the two-fluid TOV equation, the properties of dark matter (DM) admixed NSs (DANSs) have been studied. Different from previous studies, we found that increase of the maximum mass and decrease of the radius of 1.4 $M_\odot$ can occur simultaneously in DANS. This stems from the fact that the equation of state (EOS) of DM can be very soft at low density but very stiff at high density. It is well known that the IU-FSU and XS models can not reproduce the neutron star (NS) with a maximum mass greater than 2.0 $M_\odot$. However, considering IU-FSU and XS models in DANS, there are always mass and interactions of DM that can reproduce a maximum mass greater than 2.0 $M_\odot$ and the radius of 1.4 $M_\odot$ below 13.7km. The difference of DANS between the DM with chiral symmetry (DMC) and the DM with meson exchange (DMM) becomes obvious when the central energy density ratio of the DM is greater than one of the NM. When the central energy density ratio of the DM is greater than one of the NM, the DMC model with the DM mass of 1000 MeV still can reproduce a maximum mass greater than 2.0 $M_\odot$ and the radius of 1.4 $M_\odot$ below 13.7km. In the same case, although the maximum mass of DANS with the DMM model is greater than 2.0 $M_\odot$ , the radius of 1.4 $M_\odot$ with the DMM model will surpass 13.7km obviously. \com{In two-fluid system, it is worth noting that the maximum mass of DANS can be larger than 3.0 $M_\odot$. As a consequence, the dimensionless tidal deformability $\Lambda_{CP}$ of DANS with 1.4 $M_\odot$, which increase with increasing the maximum mass of DANS, could be larger than 800 when the radius of DANS with 1.4 $M_\odot$ is about 13.0km.}

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Disk heating and bending instability in galaxies with counterrotation

Astronomy and Astrophysics ◽

10.1051/0004-6361/201629032 ◽

2017 ◽

Vol 597 ◽

pp. A103 ◽

Cited By ~ 7

Author(s):

Sergey Khoperskov ◽

Giuseppe Bertin

Keyword(s):

Vertical Direction ◽

Disk Galaxies ◽

Unusual Behavior ◽

Bending Waves ◽

Integral Field Spectroscopy ◽

Pressure Anisotropy ◽

Disk Plane ◽

A Minor ◽

Dispersion Ratio

With the help of high-resolution long-slit and integral-field spectroscopy observations, the number of confirmed cases of galaxies with counterrotation is increasing rapidly. The evolution of such counterrotating galaxies remains far from being well understood. In this paper we study the dynamics of counterrotating collisionless stellar disks by means of N-body simulations. We show that, in the presence of counterrotation, an otherwise gravitationally stable disk can naturally generate bending waves accompanied by strong disk heating across the disk plane, that is in the vertical direction. Such a conclusion is found to hold even for dynamically warm systems with typical values of the initial vertical-to-radial velocity dispersion ratio σz/σR ≈ 0.5, for which the role of pressure anisotropy should be unimportant. We note that, during evolution, the σz/σR ratio tends to rise up to values close to unity in the case of locally Jeans-stable disks, whereas in disks that are initially Jeans-unstable it may reach even higher values, especially in the innermost regions. This unusual behavior of the σz/σR ratio in galaxies with counterrotation appears not to have been noticed earlier. Our investigations of systems made of two counterrotating components with different mass-ratios suggest that even apparently normal disk galaxies (i.e., with a minor counterrotating component so as to escape detection in current observations) might be subject to significant disk heating especially in the vertical direction.

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I-Love-Q anisotropically: Universal relations for compact stars with scalar pressure anisotropy

Physical Review D ◽

10.1103/physrevd.91.123008 ◽

2015 ◽

Vol 91 (12) ◽

Cited By ~ 23

Author(s):

Kent Yagi ◽

Nicolás Yunes

Keyword(s):

Compact Stars ◽

Pressure Anisotropy

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Nonlinear oscillations of compact stars in the vicinity of the maximum mass configuration

EPL (Europhysics Letters) ◽

10.1209/0295-5075/111/29001 ◽

2015 ◽

Vol 111 (2) ◽

pp. 29001 ◽

Cited By ~ 1

Author(s):

A. Brillante ◽

I. N. Mishustin

Keyword(s):

Nonlinear Oscillations ◽

Compact Stars ◽

Maximum Mass

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H-cluster stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312024416 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 435-437

Author(s):

X. Y. Lai ◽

R. X. Xu

Keyword(s):

Low Temperature ◽

Experimental Evidence ◽

Lattice Qcd ◽

Dense Matter ◽

Experimental Tests ◽

Degree Of Freedom ◽

Compact Stars ◽

Maximum Mass ◽

Cold Dense Matter ◽

Stiffening Effect

AbstractThe study of dense matter at ultra-high density has a very long history, which is meaningful for us to understand not only cosmic events in extreme circumstances but also fundamental laws of physics. In compact stars at only a few nuclear densities but low temperature, quarks could be interacting strongly with each other. That might produce quarks grouped in clusters, although the hypothetical quark-clusters in cold dense matter have not been confirmed due to the lack of both theoretical and experimental evidence. A so-called H-cluster matter is proposed in this paper as the nature of dense matter in reality.Motivated by recent lattice QCD simulations of the H-dibaryons (with structure uuddss), we are therefore considering here a possible kind of quark-clusters, H-clusters, that could emerge inside compact stars during their initial cooling, as the dominant components inside (the degree of freedom could then be H-clusters there). We study the stars composed of H-clusters, i.e., H-cluster stars, and derive the dependence of their maximum mass on the in-medium stiffening effect, showing that the maximum mass could be well above 2 M⊙ as observed and that the resultant mass-radius relation fits the measurement of the rapid burster under reasonable parameters. Besides a general understanding of different manifestations of compact stars, we expect further observational and experimental tests for the H-cluster stars in the future.

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