We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chi...We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.展开更多
Research on the properties of neutron stars with dark energy is a particularly interesting yet unresolved problem in astrophysics.We analyze the influence of dark energy on the equation of state,the maximum mass,the s...Research on the properties of neutron stars with dark energy is a particularly interesting yet unresolved problem in astrophysics.We analyze the influence of dark energy on the equation of state,the maximum mass,the surface gravitational redshift and the Keplerian frequency for the traditional neutron star and the hyperon star matter within the relativistic mean field theory,using the GM1 and TM1 parameter sets by considering the two flavor symmetries of SU(6)and SU(3)combined with the observations of PSR J1614-2230,PSR J0348+0432,PSR J0030+0451,RX J0720.4-3125,and 1E 1207.4-5209.It is found that the existence of dark energy leads to the softened equations of the state of the traditional neutron star and the hyperon star.The radius of a fixed-mass traditional neutron star(or hyperon star)with dark energy becomes smaller,which leads to increased compactness.The existence of dark energy can also enhance the surface gravitational redshift and the Keplerian frequency of traditional neutron stars and hyperon stars.The growth of the Keplerian frequency may cause the spin rate to speed up,which may provide a possible way to understand and explain the pulsar glitch phenomenon.Specifically,we infer that the mass and the surface gravitational redshift of PSR J1748-2446ad without dark energy for the GM1(TM1)parameter set are 1.141 M_(☉)(1.309 M_(☉))and 0.095(0.105),respectively.The corresponding values for the GM1(TM1)parameter set are 0.901 M_(☉)(1.072M_(☉))and 0.079(0.091)if PSR J1748-2446ad contains dark energy withα=0.05.PSR J1748-2446ad may be a low-mass pulsar with a lower surface gravitational redshift under our selected models.展开更多
In this paper,we constrain the symmetry energy at high densities in nuclear matter using recent observations of neutron stars based on the calculations of relativistic mean-field models.Using the observations of the n...In this paper,we constrain the symmetry energy at high densities in nuclear matter using recent observations of neutron stars based on the calculations of relativistic mean-field models.Using the observations of the neutron stars,we obtain the constraint on the symmetry energy at high densities,S(2_(ρ_(0)))=40.54±12.47 MeV,and S(3_(ρ_(0)))=44.12±29.38 MeV.展开更多
In this work,we analyze black hole-neutron star(BHNS)events using an astrophysically-motivated prior to derive updated,more tightly constrained estimates for component masses,mass ratios,and effective inspiral spin.Fo...In this work,we analyze black hole-neutron star(BHNS)events using an astrophysically-motivated prior to derive updated,more tightly constrained estimates for component masses,mass ratios,and effective inspiral spin.For most BHNS systems,the mean primary mass shifts to higher values,with significant cases such as GW190426 and GW200115,where the primary mass is entirely excluded from the lower-mass gap.While the primary mass of GW230529 remains within the gap,its mean value shifts slightly upward.In contrast,the secondary mass generally shifts toward the higher end of the mass spectrum.These changes highlight the substantial influence of prior choices-particularly the spin prior-on the inferred mass distributions.Additionally,for all BHNS events,the effective inspiral spin is tightly concentrated around zero,reinforcing the expectation of nearly nonspinning components in these systems.We also discuss the classical common-envelope formation scenario,which is widely considered the dominant channel for BHNS formation,where the BH formed from the more massive progenitor star is typically expected to have negligible spin.展开更多
We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the...We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the deltas can be present and even a first-order phase transition may take place, making the EOS sorer and the maximum mass of neutron stars smaller. The presence of the deltas leads to the rapid decrease of neutrino mean free paths.展开更多
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
In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the st...In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g^2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g^2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed.展开更多
In the framework of the Thomas-Fermi approximation,we systematically study the EOSs and microscopic structures of neutron star matter in a vast density range with n_(b)≈10^(-10)-2 fm^(-3),where various covariant dens...In the framework of the Thomas-Fermi approximation,we systematically study the EOSs and microscopic structures of neutron star matter in a vast density range with n_(b)≈10^(-10)-2 fm^(-3),where various covariant density functionals are adopted,i.e.,those with nonlinear self couplings(NL3,PK1,TM1,GM1,MTVTC)and density-dependent couplings(DD-LZ1,DDME-X,PKDD,DDME2,DD2,TW99).It is found that the EOSs generally coincide with each other at nb■10^(-4)fm^(-3)and 0.1 fm^(-3)■n_(b)■0.3 fm^(-3),while in other density regions they are sensitive to the effective interactions between nucleons.By adopting functionals with a larger slope of symmetry energy L,the curvature parameter K_(sym)and neutron drip density generally increases,while the droplet size,proton number of nucleus,core-crust transition density,and onset density of non-spherical nuclei,decrease.All functionals predict neutron stars with maximum masses exceeding the two-solar-mass limit,while those of DD2,DD-LZ1,DD-ME2,and DDME-X predict optimum neutron star radii according to the observational constraints.Nevertheless,the corresponding skewness coefficients J are much larger than expected,while only the functionals MTVTC and TW99 meet the start-of-art constraints on J.More accurate measurements on the radius of PSR J0740+6620 and the maximum mass of neutron stars are thus essential to identify the functional that satisfies all constraints from nuclear physics and astrophysical observations.Approximate linear correlations between neutron stars’radii at M=1.4M⊙and 2M⊙,the slope L and curvature parameter K_(sym)of symmetry energy are observed as well,which are mainly attributed to the curvature-slope correlations in the functionals adopted here.The results presented here are applicable for investigations of the structures and evolutions of compact stars in a unified manner.展开更多
β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni（β-）^67Cu and ^62Mn（β-）^62Fe are investigated as examples. The results show that a weak ...β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni（β-）^67Cu and ^62Mn（β-）^62Fe are investigated as examples. The results show that a weak magnetic field has little effect on β decay but a strong magnetic field （B 〉 10^12G） increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.展开更多
The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The inf...The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The influence of the hyperon interactions on hyperon populations in neutron star matter is discussed. The results manifest that when the ratio of the hyperon-to-nucleon couplings increases, all hyperons appear towards low baryon density direction.展开更多
A unified description of finite nuclei and equation of state of neutron stars presents both a major challenge and also opportunities for understanding nuclear interactions.Inspired by the Lee-Huang-Yang formula of har...A unified description of finite nuclei and equation of state of neutron stars presents both a major challenge and also opportunities for understanding nuclear interactions.Inspired by the Lee-Huang-Yang formula of hardsphere gases,we develop effective nuclear interactions with an additional high-order density dependent term.While the original Skyrme force SLy4 is widely used in studies of neutron stars,there are not satisfactory global descriptions of finite nuclei.The refitted SLy4' force can improve descriptions of finite nuclei but slightly reduces the radius of neutron star of 1.4 M_☉ with M_☉ being the solar mass.We find that the extended SLy4 force with a higher-order density dependence can properly describe properties of both finite nuclei and GW170817 binary neutron stars,including the mass-radius relation and the tidal deformability.This demonstrates the essential role of high-order density dependence at ultrahigh densities.Our work provides a unified and predictive model for neutron stars,as well as new insights for the future development of effective interactions.展开更多
I have studied the initial velocity（Maxwellian and exponential distributions） and the scale height of isolated old（aged≥10^9yr） neutron stars（NSs） at different Galactocentric distances R in three population mod...I have studied the initial velocity（Maxwellian and exponential distributions） and the scale height of isolated old（aged≥10^9yr） neutron stars（NSs） at different Galactocentric distances R in three population models. The smooth time-independent 3-D axisymmetric gravitational potentials（MiyamotoNagai and Paczy n′ski models） were also used. The correlation between these quantities significantly affects the shapes of the profiles and distributions of the simulated sample, because the differences in the initial kick can arise from differences in the formation and evolution of NSs with other physical parameters. The scale height of the density distribution increases systematically with R. I have also shown that the distribution of old NSs in these population models agrees with the observed structure of the Galaxy in terms of initial velocities（1-D and 3-D）, as well as the scale height distributions. These distributions tend to have an asymptotic behavior at the point R = 2.75 kpc. This means that the quality of the models can be described in terms of a mean of the fitted Gaussian, and this could also give an overall perspective of the phase space properties of nearby old NSs on a given gravitational potential.展开更多
We investigate the ^3PF2 neutron superfluidity in H-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a ...We investigate the ^3PF2 neutron superfluidity in H-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the threebody force effect on the ^3PF2 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the ^3PF2 neutron superfluidity in neutron star matter and neutron stars.展开更多
We study the properties of dense matter at finite temperature with various proton fractions for use in supernova simulations. The relativistic mean-field theory is used to describe homogeneous nuclear matter, while th...We study the properties of dense matter at finite temperature with various proton fractions for use in supernova simulations. The relativistic mean-field theory is used to describe homogeneous nuclear matter, while the Thomas-Fermi approximation is adopted to describe inhomogeneous matter. We also discuss the equation of state of neutron star matter at zero temperature in a wide density range. The equation of state at high densities can be significantly softened by the inclusion of hyperons.展开更多
The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor...The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.展开更多
The impact of symmetry energy slope L on the axial w-mode oscillations is explored, where the range of the con- strained slope L of symmetry energy at saturation density is adopted from 25 MeV to 115 MeV while keeping...The impact of symmetry energy slope L on the axial w-mode oscillations is explored, where the range of the con- strained slope L of symmetry energy at saturation density is adopted from 25 MeV to 115 MeV while keeping the equation of state （EOS） of symmetric nuclear matter fixed. Based on the range of the symmetry energy slope, a constraint on the frequency and damping time of the wi-mode of the neutron star is given. It is found that there is a perfect linear relation between the frequency and the stellar mass for a fixed slope L, and the softer symmetry energy corresponds to a higher frequency. Moreover, it is confirmed that both the frequencies and damping times have a perfect universal scaling behavior for the EOSs with different symmetry energy slopes at saturation density.展开更多
In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates ...In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10^5 - 10^13g on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10^13 to 10^18 G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.展开更多
The imprints of the neutron star crust on the gravitational waves emitted from the axial w-modes are investigated by adopting two typical equations of state （EOSs） of the crust matter and two representative EOSs of ...The imprints of the neutron star crust on the gravitational waves emitted from the axial w-modes are investigated by adopting two typical equations of state （EOSs） of the crust matter and two representative EOSs of the core matter. It is shown that there is a significant effect of the crust EOSs on the gravitational waves from the axial w-mode oscillation for a stiff core EOS.展开更多
In the framework of the relativistic mean field theory, the isovector scalar interaction is considered by exchanging δ meson to study the influence of δ meson on the cooling properties of neutron star matter. The ca...In the framework of the relativistic mean field theory, the isovector scalar interaction is considered by exchanging δ meson to study the influence of δ meson on the cooling properties of neutron star matter. The calculation results show that with the inclusion of δ meson, the neutrino emissivity of the direct Urca processes increases, and thus enhances the cooling of neutron star matter. When strong proton superfluidity is considered, the theoretical cooling curves agree with the observed thermal radiation for isolated neutron stars.展开更多
The influences of electron screening （ES） and electron energy correction （EEC） are investigated by superstrong magnetic field （SMF）. We also discuss in detail the discrepant factor between our results and those ...The influences of electron screening （ES） and electron energy correction （EEC） are investigated by superstrong magnetic field （SMF）. We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick （FGP） in SMF. The results show that SMF has only a slight effect on ES when B 〈 10^9 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B 〉 10^9 T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μe = 1.0 × 10^6 mol/cm^3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP＇s when B 〈 10^9 T . But the difference will be increased with increasing SMF.展开更多
文摘We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.
基金partially funded by the Horizontal Scientific Research Project of the National Astronomical Observatories of CAS(Grant No.E0900501)and the Theoretical Fundamental Research Special Project of the Changchun Observatory,National Astronomical Observatories,CAS(Grant No.Y990000205)。
文摘Research on the properties of neutron stars with dark energy is a particularly interesting yet unresolved problem in astrophysics.We analyze the influence of dark energy on the equation of state,the maximum mass,the surface gravitational redshift and the Keplerian frequency for the traditional neutron star and the hyperon star matter within the relativistic mean field theory,using the GM1 and TM1 parameter sets by considering the two flavor symmetries of SU(6)and SU(3)combined with the observations of PSR J1614-2230,PSR J0348+0432,PSR J0030+0451,RX J0720.4-3125,and 1E 1207.4-5209.It is found that the existence of dark energy leads to the softened equations of the state of the traditional neutron star and the hyperon star.The radius of a fixed-mass traditional neutron star(or hyperon star)with dark energy becomes smaller,which leads to increased compactness.The existence of dark energy can also enhance the surface gravitational redshift and the Keplerian frequency of traditional neutron stars and hyperon stars.The growth of the Keplerian frequency may cause the spin rate to speed up,which may provide a possible way to understand and explain the pulsar glitch phenomenon.Specifically,we infer that the mass and the surface gravitational redshift of PSR J1748-2446ad without dark energy for the GM1(TM1)parameter set are 1.141 M_(☉)(1.309 M_(☉))and 0.095(0.105),respectively.The corresponding values for the GM1(TM1)parameter set are 0.901 M_(☉)(1.072M_(☉))and 0.079(0.091)if PSR J1748-2446ad contains dark energy withα=0.05.PSR J1748-2446ad may be a low-mass pulsar with a lower surface gravitational redshift under our selected models.
基金supported by the National Natural Science Foundation of China(Nos.12275359,12375129,11875323,and 11961141003)the National Key R&D Program of China(No.2023YFA1606402)+2 种基金the Continuous Basic Scientific Research Project,the China Institute of Atomic Energy(Nos.YZ222407001301 and YZ232604001601)the Leading Innovation Project of the CNNC(Nos.LC192209000701 and LC202309000201)the computing server SCATP in China Institute of Atomic Energy and Basic Research Special Zone.
文摘In this paper,we constrain the symmetry energy at high densities in nuclear matter using recent observations of neutron stars based on the calculations of relativistic mean-field models.Using the observations of the neutron stars,we obtain the constraint on the symmetry energy at high densities,S(2_(ρ_(0)))=40.54±12.47 MeV,and S(3_(ρ_(0)))=44.12±29.38 MeV.
基金support of the undergraduate Innovation and Entrepreneurship Training Program(No.S202410370441)the Undergraduate Outstanding Thesis Cultivation Program(No.pyjh2024291)+2 种基金support from Anhui Provincial Natural Science Foundation(grant No.2308085MA29)supported by the National Natural Science Foundation of China(grant Nos.12473036 and 12103003)supported by Jiangxi Provincial Natural Science Foundation(grant Nos.20242BAB26012 and 20224ACB211001)。
文摘In this work,we analyze black hole-neutron star(BHNS)events using an astrophysically-motivated prior to derive updated,more tightly constrained estimates for component masses,mass ratios,and effective inspiral spin.For most BHNS systems,the mean primary mass shifts to higher values,with significant cases such as GW190426 and GW200115,where the primary mass is entirely excluded from the lower-mass gap.While the primary mass of GW230529 remains within the gap,its mean value shifts slightly upward.In contrast,the secondary mass generally shifts toward the higher end of the mass spectrum.These changes highlight the substantial influence of prior choices-particularly the spin prior-on the inferred mass distributions.Additionally,for all BHNS events,the effective inspiral spin is tightly concentrated around zero,reinforcing the expectation of nearly nonspinning components in these systems.We also discuss the classical common-envelope formation scenario,which is widely considered the dominant channel for BHNS formation,where the BH formed from the more massive progenitor star is typically expected to have negligible spin.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10575005 and 10435080the Key Grant Project of the Ministry of Education under Grant No.305001
文摘We have investigated the possibility of the presence of the deltas in neutron star matter and their effects on neutron stars. Δ-meson couplings of the theoretical predictions are only restricted in a region where the deltas can be present and even a first-order phase transition may take place, making the EOS sorer and the maximum mass of neutron stars smaller. The presence of the deltas leads to the rapid decrease of neutrino mean free paths.
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Supported by Jiangsu Province Natural Science Foundation Youth Fund of China under Grant No.Bk20140982National Natural Science Foundation of China under Grant No.11447165+1 种基金Youth Innovation Promotion Association,Chinese Academy of Sciences under Grant No.2016056the Development Project of Science and Technology of Jilin Province under Grant No.20180520077JH
文摘In the framework of the relativistic mean field theory including the hyperon-hyperon(YY) interactions,protoneutron stars with a weakly interacting light U boson are studied. The U-boson leads to the increase of the star maximum mass. The modification to the maximum mass by the U-boson with the strong YY interaction is larger than that with the weak YY interaction. The maximum mass of the protoneutron star is less sensitive to the U-boson than that of the neutron star. The inclusion of the U-boson narrows down the mass window for the hyperonized protoneutron stars. As g^2/μ~2 increases, the species of hyperons, which can appear in a stable protoneutron star decrease. The rotation frequency, the red shift, the momentum of inertia and the total neutrino fraction of PSR J1903-0327 are sensitive to the U-boson and change with g^2/μ~2 in an approximate linear trend. The possible way to constrain the coupling constants of the U-boson is discussed.
基金supported by National SKA Program of China No.2020SKA0120300National Natural Science Foundation of China(Grant No.11875052,No.11873040,No.11705163,and No.11525524)+3 种基金the science research grants from the China Manned Space Project(No.CMS-CSST-2021-B11)the Youth Innovation Fund of Xiamen(No.3502Z20206061)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2021-sp36)the National Key R&D Program of China No.2018YFA0404402
文摘In the framework of the Thomas-Fermi approximation,we systematically study the EOSs and microscopic structures of neutron star matter in a vast density range with n_(b)≈10^(-10)-2 fm^(-3),where various covariant density functionals are adopted,i.e.,those with nonlinear self couplings(NL3,PK1,TM1,GM1,MTVTC)and density-dependent couplings(DD-LZ1,DDME-X,PKDD,DDME2,DD2,TW99).It is found that the EOSs generally coincide with each other at nb■10^(-4)fm^(-3)and 0.1 fm^(-3)■n_(b)■0.3 fm^(-3),while in other density regions they are sensitive to the effective interactions between nucleons.By adopting functionals with a larger slope of symmetry energy L,the curvature parameter K_(sym)and neutron drip density generally increases,while the droplet size,proton number of nucleus,core-crust transition density,and onset density of non-spherical nuclei,decrease.All functionals predict neutron stars with maximum masses exceeding the two-solar-mass limit,while those of DD2,DD-LZ1,DD-ME2,and DDME-X predict optimum neutron star radii according to the observational constraints.Nevertheless,the corresponding skewness coefficients J are much larger than expected,while only the functionals MTVTC and TW99 meet the start-of-art constraints on J.More accurate measurements on the radius of PSR J0740+6620 and the maximum mass of neutron stars are thus essential to identify the functional that satisfies all constraints from nuclear physics and astrophysical observations.Approximate linear correlations between neutron stars’radii at M=1.4M⊙and 2M⊙,the slope L and curvature parameter K_(sym)of symmetry energy are observed as well,which are mainly attributed to the curvature-slope correlations in the functionals adopted here.The results presented here are applicable for investigations of the structures and evolutions of compact stars in a unified manner.
基金Project suoported by the National Natural Science Foundation of China （Grant No 10347008）.
文摘β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni（β-）^67Cu and ^62Mn（β-）^62Fe are investigated as examples. The results show that a weak magnetic field has little effect on β decay but a strong magnetic field （B 〉 10^12G） increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10047001 and 10275029+2 种基金the State Key Basic Research Development Program under Grant No.G2000-0774-07the CAS Knowledge Innovation Project under Contract No.KJCX2-SW-N02
文摘The numerical results of the populations for the baryon octet in neutron star matter have been presented by solving a set transcendental equations in the framework of the relativistic mean field approximation. The influence of the hyperon interactions on hyperon populations in neutron star matter is discussed. The results manifest that when the ratio of the hyperon-to-nucleon couplings increases, all hyperons appear towards low baryon density direction.
基金Supported by the National Key R&D Program of China (Grant No.2018YFA0404403)the National Natural Science Foundation of China (Grant Nos.11975032,11835001,11790325,and 11961141003)。
文摘A unified description of finite nuclei and equation of state of neutron stars presents both a major challenge and also opportunities for understanding nuclear interactions.Inspired by the Lee-Huang-Yang formula of hardsphere gases,we develop effective nuclear interactions with an additional high-order density dependent term.While the original Skyrme force SLy4 is widely used in studies of neutron stars,there are not satisfactory global descriptions of finite nuclei.The refitted SLy4' force can improve descriptions of finite nuclei but slightly reduces the radius of neutron star of 1.4 M_☉ with M_☉ being the solar mass.We find that the extended SLy4 force with a higher-order density dependence can properly describe properties of both finite nuclei and GW170817 binary neutron stars,including the mass-radius relation and the tidal deformability.This demonstrates the essential role of high-order density dependence at ultrahigh densities.Our work provides a unified and predictive model for neutron stars,as well as new insights for the future development of effective interactions.
文摘I have studied the initial velocity（Maxwellian and exponential distributions） and the scale height of isolated old（aged≥10^9yr） neutron stars（NSs） at different Galactocentric distances R in three population models. The smooth time-independent 3-D axisymmetric gravitational potentials（MiyamotoNagai and Paczy n′ski models） were also used. The correlation between these quantities significantly affects the shapes of the profiles and distributions of the simulated sample, because the differences in the initial kick can arise from differences in the formation and evolution of NSs with other physical parameters. The scale height of the density distribution increases systematically with R. I have also shown that the distribution of old NSs in these population models agrees with the observed structure of the Galaxy in terms of initial velocities（1-D and 3-D）, as well as the scale height distributions. These distributions tend to have an asymptotic behavior at the point R = 2.75 kpc. This means that the quality of the models can be described in terms of a mean of the fitted Gaussian, and this could also give an overall perspective of the phase space properties of nearby old NSs on a given gravitational potential.
基金supported in part by the National Natural Science Foundation of China (Grant Nos 10575119 and 10775061)the Knowledge Innovation Project (Grant No KJCX3-SYW-N2) of Chinese Academy of Sciences+2 种基金the Major State Basic Research Developing Program of China (Grant No 2007CB815004)CAS/SAFEA International Partnership Program for Creative Research Teams(Grant No CXTD-J2005-1)the Asia-Link project (Grant No CN/ASIA-LINK/008(94791)) of the European Commission
文摘We investigate the ^3PF2 neutron superfluidity in H-stable neutron star matter and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the threebody force effect on the ^3PF2 neutron pairing gap. It is found that the three-body force effect is to enhance remarkably the ^3PF2 neutron superfluidity in neutron star matter and neutron stars.
基金supported by National Natural Science Foundation of China(Nos.10675064,11075082)
文摘We study the properties of dense matter at finite temperature with various proton fractions for use in supernova simulations. The relativistic mean-field theory is used to describe homogeneous nuclear matter, while the Thomas-Fermi approximation is adopted to describe inhomogeneous matter. We also discuss the equation of state of neutron star matter at zero temperature in a wide density range. The equation of state at high densities can be significantly softened by the inclusion of hyperons.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11447165,11373047 and 11265009the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2016056
文摘The relativistic neutrino emissivity of the nucleonic direct URCA processes in neutron star matter is investigated within the relativistic Hartree-Fock approximation. We particularly study the influences of the tensor couplings of vector mesons ω and ρ on the nucleonic direct URCA processes. It is found that the inclusion of the tensor couplings of vector mesons w and p can slightly increase the maximum mass of neutron stars. In addition, the results indicate that the tensor couplings of vector mesons ω and ρ lead to obvious enhancement of the total neutrino emissivity for the nucleonic direct URCA processes, which must accelerate the cooling rate of the non- superfluid neutron star matter. However, when considering only the tensor coupling of vector meson ρ, the neutrino emissivity for the nucleonic direct URCA processes slightly declines at low densities and significantly increases at high densities. That is, the tensor coupling of vector meson ρ leads to the slow cooling rate of a low-mass neutron star and rapid cooling rate of a massive neutron star.
基金supported by the National Natural Science Foundation of China(Grant Nos.10947023 and 11275073)the Fundamental Research Funds for the Central Universities(Grant No.2012ZZ0079)sponsored by SRF for ROCS,SEM
文摘The impact of symmetry energy slope L on the axial w-mode oscillations is explored, where the range of the con- strained slope L of symmetry energy at saturation density is adopted from 25 MeV to 115 MeV while keeping the equation of state （EOS） of symmetric nuclear matter fixed. Based on the range of the symmetry energy slope, a constraint on the frequency and damping time of the wi-mode of the neutron star is given. It is found that there is a perfect linear relation between the frequency and the stellar mass for a fixed slope L, and the softer symmetry energy corresponds to a higher frequency. Moreover, it is confirmed that both the frequencies and damping times have a perfect universal scaling behavior for the EOSs with different symmetry energy slopes at saturation density.
基金Project supported by the National Natural Science Foundation of China （Grant No 10347008）.
文摘In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10^5 - 10^13g on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10^13 to 10^18 G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10947023)the Fundamental Research Funds for the Central University, China (Grant No. 2009ZM0193)
文摘The imprints of the neutron star crust on the gravitational waves emitted from the axial w-modes are investigated by adopting two typical equations of state （EOSs） of the crust matter and two representative EOSs of the core matter. It is shown that there is a significant effect of the crust EOSs on the gravitational waves from the axial w-mode oscillation for a stiff core EOS.
基金supported by National Natural Science Foundation of China (Nos.10675024,11075063)National Fundamental Fund Project of Subsidy Funds of Personnel Training of China (J0730311)
文摘In the framework of the relativistic mean field theory, the isovector scalar interaction is considered by exchanging δ meson to study the influence of δ meson on the cooling properties of neutron star matter. The calculation results show that with the inclusion of δ meson, the neutrino emissivity of the direct Urca processes increases, and thus enhances the cooling of neutron star matter. When strong proton superfluidity is considered, the theoretical cooling curves agree with the observed thermal radiation for isolated neutron stars.
基金supported by the Natural Science Foundation of Hainan Province,China (Grant No.109004)the Scientific Research and Foundation of Hainan Provincial Education Department,China (Grant No.Hjkj2010-42)the Special Foundation of Institutions for Higher Education of Sanya (Grant No.YD09047)
文摘The influences of electron screening （ES） and electron energy correction （EEC） are investigated by superstrong magnetic field （SMF）. We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick （FGP） in SMF. The results show that SMF has only a slight effect on ES when B 〈 10^9 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B 〉 10^9 T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μe = 1.0 × 10^6 mol/cm^3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP＇s when B 〈 10^9 T . But the difference will be increased with increasing SMF.
