The Chandrasekhar-Friedmann-Schutz （CFS） instabilities of r-modes for canonical neutron stars （1.4 Me） with rigid crusts are investigated by using an equation of state of asymmetric nuclear matter with super-soft ...The Chandrasekhar-Friedmann-Schutz （CFS） instabilities of r-modes for canonical neutron stars （1.4 Me） with rigid crusts are investigated by using an equation of state of asymmetric nuclear matter with super-soft symmetry energy, where the non-Newtonian gravity proposed in the grand unification theories is also considered. Constrained by the observations of the masses and the spin frequencies for neutron stars, the boundary of the r-mode instability window for a canonical neutron star is obtained, and the results show that the observed neutron stars are all outside the instability window, which is consistent with the theoretical expectation. In addition, an upper limit of the non-Newtonian gravity parameters is also given.展开更多
The bulk viscosity of interacting strange quark matter in a strong external magnetic field B m with a real equation of state is investigated.It is found that interquark interactions can significantly increase the bulk...The bulk viscosity of interacting strange quark matter in a strong external magnetic field B m with a real equation of state is investigated.It is found that interquark interactions can significantly increase the bulk viscosity,and the magnetic field B_(m) can cause irregular oscillations in both components of the bulk viscosity,ξ||(parallel to B_(m))and ξ⊥(perpendicular to B_(m)).A comparison with non-interacting strange quark matter reveals that when B_(m) is sufficiently large,ξ⊥is more affected by interactions than ξ||.Additionally,the quasi-oscillation of the bulk viscosity with changes in density may facilitate the for-mation of magnetic domains.Moreover,the resulting r-mode instability windows are in good agreement with observational data for compact stars in low-mass X-ray binaries.Specifically,the r-mode instability window for interacting strange quark matter in high magnetic fields has a minimum rotation frequency exceeding 1050 Hz,which may explain the observed very high spin frequency of a pulsar with V=1122 Hz.展开更多
We investigate the bulk viscosity of strange quark matter in the framework of the equivparticle model,where analytical formulae are obtained for certain temperature ranges,which can be readily applied to those with va...We investigate the bulk viscosity of strange quark matter in the framework of the equivparticle model,where analytical formulae are obtained for certain temperature ranges,which can be readily applied to those with various quark mass scalings.In the case of adopting a quark mass scaling with both linear confinement and perturbative interactions,the obtained bulk viscosity increases by 1-2 orders of magnitude compared with those in bag model scenarios.Such an enhancement is mainly due to the large quark equivalent masses adopted in the equivparticle model,which are essentially attributed to the strong interquark interactions and are related to the dynamical chiral symmetry breaki ng.Due to the high bulk viscosity,the predicted damping time of oscillatio ns for a can on ical 1.4 M⊙ strange star is less than one millisecond,which is shorter than previous findings.Consequently,the obtained r-mode instability window for the canonical strange stars well accommodates the observational frequencies and temperatures for pulsars in low-mass X-ray binaries(LMXBs).展开更多
The magnetic damping rate was introduced in the evolution equations of r-modes,which shows that r-modes can generate strong toroidal magnetic fields in the core of accreting millisecond pulsars inducing by differentia...The magnetic damping rate was introduced in the evolution equations of r-modes,which shows that r-modes can generate strong toroidal magnetic fields in the core of accreting millisecond pulsars inducing by differential rotation.With consideration of the coupling evolution of r-modes,spin and thermal evolution,we investigated the influence of the magnetic damping on the differential rotation of nonlinear r-modes of accreting neutron stars.We derived the coupling evolution equations of the star involving the magnetic damping rate in the framework of second-order r-mode theory.The numerical results show that the magnetic damping suppressed the nonlinear evolution of r-modes since the saturation amplitude is reduced to a great extent.In particular,because of the presence of the generated toroidal magnetic field,the spin-down of the stars is terminated and the viscous heating effects are also weakened.Moreover,we could obtain a stronger generated toroidal magnetic field in the second-order r-mode theory.The gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation is small when the r-mode instability becomes active and the accretion rate is not very high.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10947023 and 11275073the Fundamental Research Funds for the Central Universities under Grant No. 2012ZZ0079the Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘The Chandrasekhar-Friedmann-Schutz （CFS） instabilities of r-modes for canonical neutron stars （1.4 Me） with rigid crusts are investigated by using an equation of state of asymmetric nuclear matter with super-soft symmetry energy, where the non-Newtonian gravity proposed in the grand unification theories is also considered. Constrained by the observations of the masses and the spin frequencies for neutron stars, the boundary of the r-mode instability window for a canonical neutron star is obtained, and the results show that the observed neutron stars are all outside the instability window, which is consistent with the theoretical expectation. In addition, an upper limit of the non-Newtonian gravity parameters is also given.
基金This work was supported by the National Natural Science Foundation of China(Nos.12005005,11947098)Key Research Projects of Universities in Henan Province(No.20A140003)。
文摘The bulk viscosity of interacting strange quark matter in a strong external magnetic field B m with a real equation of state is investigated.It is found that interquark interactions can significantly increase the bulk viscosity,and the magnetic field B_(m) can cause irregular oscillations in both components of the bulk viscosity,ξ||(parallel to B_(m))and ξ⊥(perpendicular to B_(m)).A comparison with non-interacting strange quark matter reveals that when B_(m) is sufficiently large,ξ⊥is more affected by interactions than ξ||.Additionally,the quasi-oscillation of the bulk viscosity with changes in density may facilitate the for-mation of magnetic domains.Moreover,the resulting r-mode instability windows are in good agreement with observational data for compact stars in low-mass X-ray binaries.Specifically,the r-mode instability window for interacting strange quark matter in high magnetic fields has a minimum rotation frequency exceeding 1050 Hz,which may explain the observed very high spin frequency of a pulsar with V=1122 Hz.
基金Supported by National Natural Science Foundation of China(12005005,11947098,11705163,11875052,No.11575190)key research projects of universities in Henan province(20A140003)。
文摘We investigate the bulk viscosity of strange quark matter in the framework of the equivparticle model,where analytical formulae are obtained for certain temperature ranges,which can be readily applied to those with various quark mass scalings.In the case of adopting a quark mass scaling with both linear confinement and perturbative interactions,the obtained bulk viscosity increases by 1-2 orders of magnitude compared with those in bag model scenarios.Such an enhancement is mainly due to the large quark equivalent masses adopted in the equivparticle model,which are essentially attributed to the strong interquark interactions and are related to the dynamical chiral symmetry breaki ng.Due to the high bulk viscosity,the predicted damping time of oscillatio ns for a can on ical 1.4 M⊙ strange star is less than one millisecond,which is shorter than previous findings.Consequently,the obtained r-mode instability window for the canonical strange stars well accommodates the observational frequencies and temperatures for pulsars in low-mass X-ray binaries(LMXBs).
基金supported by the West Light Foundation of Chinese Academy of Sciences(Grant No.ZD201302)National Natural Science Foundation of China(Grant Nos.11373006 and11003034)the Key Laboratory of Radio Astronomy,Chinese Academy of Sciences
文摘The magnetic damping rate was introduced in the evolution equations of r-modes,which shows that r-modes can generate strong toroidal magnetic fields in the core of accreting millisecond pulsars inducing by differential rotation.With consideration of the coupling evolution of r-modes,spin and thermal evolution,we investigated the influence of the magnetic damping on the differential rotation of nonlinear r-modes of accreting neutron stars.We derived the coupling evolution equations of the star involving the magnetic damping rate in the framework of second-order r-mode theory.The numerical results show that the magnetic damping suppressed the nonlinear evolution of r-modes since the saturation amplitude is reduced to a great extent.In particular,because of the presence of the generated toroidal magnetic field,the spin-down of the stars is terminated and the viscous heating effects are also weakened.Moreover,we could obtain a stronger generated toroidal magnetic field in the second-order r-mode theory.The gravitational radiation may be detected by the advanced laser interferometer detector LIGO if the amount of differential rotation is small when the r-mode instability becomes active and the accretion rate is not very high.
