Exploring the state of ultra-cold supranuclear dense matter that makes up the cores of massive neutron stars is one of the greatest unresolved problems in modern physics. In this letter, we show that when the interior...Exploring the state of ultra-cold supranuclear dense matter that makes up the cores of massive neutron stars is one of the greatest unresolved problems in modern physics. In this letter, we show that when the interiors of pulsars are made of compressible and dissipative normal matter, the commonly used solution procedures combined with the known EOSs yield widely scattered solutions and poorly determined radii. A remarkable agreement emerges, however, if pulsars harbour cores that are made of incompressible entropy-free superfluids (SuSu-matter) embedded in flat spacetimes. Such supranuclear dense matter should condensate to form false vacua as predicated by non-perterbative QCD vacuum. The solutions here are found to be physically consistent and mathematically elegant, irrespective of the object’s mass. Based thereon, we conclude that the true masses of massive NSs may differ significantly from those revealed by direct observation.展开更多
So far among the nineteen pairs of detected double neutron star(DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic...So far among the nineteen pairs of detected double neutron star(DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic age of 113 kyr, is one of the three detected DNS as a non-recycled and second-born NS, which is believed to be formed by an electron capture or a low energy ultra-stripped iron core-collapse supernova(SN) explosion. The SN remnant around PSR J1906+0746 is too dim to be observed by optical telescopes, then its x-ray flux limit has been given by Chandra. A reference pulsar PSR J1509-5850 with the young characteristic age of 154 kyr was chosen as an object of comparison, which has an SN remnant observed by Chandra and is believed to be formed by iron core SN explosion. We impose a restriction on the maximum kinetic energy of electron-capture(EC) SN explosion that induces the formation of PSR J1906+0746. The estimated result is(4–8)×10^(50) erg(1 erg= 10-7 J), which is consistent with that of the published simulations of the EC process, i.e., a lower value than that of the conventional iron core SN explosion of(1–2)×10^(51) erg. As suggested, EC process for NS formation is pertained to the subluminous type Ic SN by the helium star with ONeMg core, thus for the first time we derived the kinetic energy of EC SN explosion of DNS, which may be reconciled with the recent observation of type Ic SN 2014 ft with kinetic energy of 2 × 10^(50) erg.展开更多
LIGO-Virgo has observed the gravitational waves(GWs)from the coalescence of binary black hole(BBH)and binary neutron star(BNS)during O1 and O2,and the ones from NS-BH are expected to be hunted in the operating O3 run....LIGO-Virgo has observed the gravitational waves(GWs)from the coalescence of binary black hole(BBH)and binary neutron star(BNS)during O1 and O2,and the ones from NS-BH are expected to be hunted in the operating O3 run.The population properties and mass distribution of NS-BH mergers are poorly understood now,thus researchers simulated their chirp mass(M)distribution by a synthetic model,in which the BHs and NSs were inferred by LIGO-Virgo(O1/O2),and obtained the values in the range of 2.1 M_(⊙)<M<7.3 M_(⊙).In this paper,we further simulate the GW frequency(fGW)distribution of NS-BH mergers by the above-stated synthetic model,with a basic binary system model through the Monte Carlo method.Our results predict that the median with 90%credible intervals is 165+475-64 Hz in the case of Schwarzschild BH when the system just before merger,and this GW frequency is expected to increase several times in the merger stage,which is lying in the frequency band of LIGO-Virgo,i.e.,about 15 Hz to a few kHz.Our results provide an important reference for hunting the NS-BH mergers by the on-going O3 run of LIGO-Virgo.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
The aspect of formation and evolution of the recycled pulsar(PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram(– diagram) in the double pu...The aspect of formation and evolution of the recycled pulsar(PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram(– diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate(or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.展开更多
Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are ...Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are embedded in Minkowski spacetime, whereas the ambient compressible and dissipative media (CDM) are imbedded in curved spacetime. As pulsars cool down, the equilibrium between both spacetime is altered, thereby triggering the well-observed glitch phenomena. Based thereon and assuming all neutron stars (<em>NSs</em>) to be born with the same initial mass of <img src="Edit_4d2d9e5f-812f-41d7-9422-5cfb3fc10997.bmp" alt="" />, we argue that the remnant of GW170817 should be a relatively faint <em>NS</em> with a massive central core made of SuSu-matter. The effective mass and radius of the remnant are predicted to be <img src="Edit_6702e3a8-abff-41f9-a45b-a2bc1e6c61b0.bmp" alt="" /> and <span style="white-space:nowrap;"><em>R</em><sub><em>rem</em></sub>=10.764 Km</span>, whereas the mass of the enclosed SuSu-core is <img src="Edit_6fe43fca-e33b-45a6-b846-bd7a09d4b8dd.bmp" alt="" />. Here, about 1/2<em>M</em><sub><em>core</em></sub> is an energy enhancement triggered by the phase transition of the gluon-quark-plasma from the microscopic into macroscopic scale. The current compactness of the remnant is <img src="Edit_38ced5f8-6f72-44d8-a3c9-89c2eaf73e0e.bmp" alt="" />, but predicted to increase as the CDM and cools down, rendering the remnant an invisible dark energy object, and therefore to an excellent black hole candidate.展开更多
In 2011, Jun Ni published the solution of the Tolman-Oppenheimer-Volkoff equations describing the structure of stable neutron stars, which implies that 1) there is no upper mass limit of these objects, 2) their outer ...In 2011, Jun Ni published the solution of the Tolman-Oppenheimer-Volkoff equations describing the structure of stable neutron stars, which implies that 1) there is no upper mass limit of these objects, 2) their outer physical surface is always situated above the corresponding event horizon, and 3) the object is a hollow sphere with the inner physical surface and cavity inside. In our paper, we propose to “purify” the general relativity, as the geometrical theory, from the concept of mass. If we get rid of the concept of mass and Newtonian-type potential, then we obtain such the behavior of gravity which results in the above mentioned stable Ni’s object. It is farther pointed out that the distribution of matter, which is observed as spherically symmetric by the observer in its center, is not longer observed as spherically symmetric by an observer aside the center in a curved spacetime of general relativity. This fact implies, in contrast to the Newtonian physics, the non-zero and outward oriented gravitational attraction of upper layers of star. Ni considered positive energy density and pressure. In addition, gravity had everywhere attractive character. No “exotic” assumption was made. Hence, there is no reason why his concept of hollow sphere should not be applicable to the models of real objects.展开更多
In a second-order r-mode theory,Sa' and Tome' found that the r-mode oscillation in neutron stars(NSs) could induce stellar differential rotation,which naturally leads to a saturated state of the oscillation.Ba...In a second-order r-mode theory,Sa' and Tome' found that the r-mode oscillation in neutron stars(NSs) could induce stellar differential rotation,which naturally leads to a saturated state of the oscillation.Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution,we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries,where the viscous damping of the r-modes and its resultant effects are taken into account.The numerical results show that,for both kinds of NSs,the differential rotation can significantly prolong the duration of the r-modes.As a result,the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years.Moreover,the persistent radiation of a quasi-monochromaticgravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation.This increases the detectability of gravitational waves from both young isolated and old accreting NSs.展开更多
The eigen-frequencies of the axial w-modes of neutron star described by a super-soft equation of state(EOS) are investigated,by considering the non-Newtonian gravity.The results show that at the same stellar mass,the ...The eigen-frequencies of the axial w-modes of neutron star described by a super-soft equation of state(EOS) are investigated,by considering the non-Newtonian gravity.The results show that at the same stellar mass,the frequencies of wI and wI2 for our model are lower than that of the typical EOSs(such as APR); and the frequencies increase with the stellar masses,which is contrary to that of the typical EOSs.These characters may provide a probe to testify the super soft symmetry energy and the non-Newtonian gravity in the future.Moreover,our model also has the universal behavior of the mass-scaled eigen-frequencies as a function of the compactness.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
When a daughter nucleus produced by electron capture takes part in a level transition from an excited state to its ground state in accreting neutron star crusts, thermal energy will be released and heat the crust, inc...When a daughter nucleus produced by electron capture takes part in a level transition from an excited state to its ground state in accreting neutron star crusts, thermal energy will be released and heat the crust, increasing crust temperature and changing subsequent carbon ignition conditions. Previous studies show that the theoretical carbon ignition depth is deeper than the value inferred from observations because the thermal energy is not sufficient. In this paper, we present the de-excited energy from electron capture of rp-process ash before carbon ignition, especially for the initial evolution stage of rp-process ash, by using a level-to-level transition method. We find the theoretical column density of carbon ignition in the resulting superbursts and compare it with observations. The calculation of the electron capture process is based on a more reliable level-to-level transition, adopting new data from experiments or theoretical models(e.g., large-scale shell model and proton-neutron quasi-particle random phase approximation). The new carbon ignition depth is estimated by fitting from previous results of a nuclear reaction network. Our results show the average de-excited energy from electron capture before carbon ignition is ~0.026 Me V/u, which is significantly larger than the previous results. This energy is beneficial for enhancing the crust’s temperature and decreasing the carbon ignition depth of superbursts.展开更多
The deconfinement phase transition from hadronic matter to quark matter in the interior of compact stars is investigated. The hadronic phase is described in the framework of relativistic mean-field theory, where the s...The deconfinement phase transition from hadronic matter to quark matter in the interior of compact stars is investigated. The hadronic phase is described in the framework of relativistic mean-field theory, where the scalar-isovector δ-meson effective field is also taken into account. The MIT bag model for describing a quark phase is used. The changes of the parameters of phase transition caused by the presence of a δ-meson field are explored. Finally, alterations in the integral and structural parameters of hybrid stars due to both a deconfinement phase transition and inclusion of a δ-meson field are discussed.展开更多
We review theoretical relations between macroscopic properties of neutron stars and microscopic quantities of nuclear matter, such as consistency of hadronic nuclear models and observed masses of neutron stars. The re...We review theoretical relations between macroscopic properties of neutron stars and microscopic quantities of nuclear matter, such as consistency of hadronic nuclear models and observed masses of neutron stars. The relativistic hadronic field theory, quantum hadrodynamics (QHD), and mean-field approximations of the theory are applied to saturation properties of symmetric nuclear and neutron matter. The equivalence between mean-field approximations and Hartree approximation is emphasized in terms of renormalized effective masses and effective coupling constants of hadrons. This is important to prove that the direct application of mean-field (Hartree) approximation to nuclear and neutron matter is inadequate to examine physical observables. The equations of state (EOS), binding energies of nuclear matter, self-consistency of nuclear matter, are reviewed, and the result of chiral Hartree-Fock ?approximation is shown. Neutron stars and history of nuclear astrophysics, nuclear model and nuclear matter, possibility of hadron and hadron-quark neutron stars are briefly reviewed. The hadronic models are very useful and practical for understanding astrophysical phenomena, nuclear matter and radiation phenomena of nuclei.展开更多
We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its s...We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.展开更多
Resonant cyclotron scattering(RCS) in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation) for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations s...Resonant cyclotron scattering(RCS) in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation) for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations show that there exist not only up scattering but also down scattering of RCS,depending on the parameter space.RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars(INSs) are pointed out.The optical/UV excess of INSs may be caused by the down scattering of RCS.The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data.In our model,the INSs are proposed to be normal neutron stars,although the quark star hypothesis is still possible.The low pulsation amplitude of INSs is a natural consequence in the RCS model.展开更多
The impact of symmetry energy slope L on the axial w-mode oscillations is explored, where the range of the constrained slope L of symmetry energy at saturation density is adopted from 25 MeV to 115 MeV while keeping t...The impact of symmetry energy slope L on the axial w-mode oscillations is explored, where the range of the constrained 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 w I -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 the framework of relativistic mean field theory,the condensations of K^- and (?)~0 in neutron star matterincluding baryon octet and Δ quartet are studied.We find that in this case K^- and (?)~0 condensations can o...In the framework of relativistic mean field theory,the condensations of K^- and (?)~0 in neutron star matterincluding baryon octet and Δ quartet are studied.We find that in this case K^- and (?)~0 condensations can occur atrelative shallow optical potential depth of (?) from -80 MeV to -160 MeV.Both K^- and (?)~0 condensations favor theappearances of Δ resonances.With (?) condensations all the Δ quartet can appear well inside the maximum mass stars.The appearances of Δ resonances change the composition and distribution of particles at high densities.The populationsof Δ resonances can enhance K^- condensation.It is found that in the core of massive neutron stars,neutron star matterincludes rich particle species,such as antikaons,baryon octet,and Δ quartet.In the presence of Δ resonances and (?)condensation,the EOS becomes softer and results in smaller maximum mass stars.Furthermore the impact of antikaoncondensations,hyperons,and Δ resonances on direct Urca process with nucleons is also discussed briefly.展开更多
We examine the effect of adding mesons fo(975) and Ф(1020) as well as the variety of UΞ^(N) (the potential well depth ofΞ in nuclear matter) from -10 MeV to -28 MeV on the extent of the particles participation and ...We examine the effect of adding mesons fo(975) and Ф(1020) as well as the variety of UΞ^(N) (the potential well depth ofΞ in nuclear matter) from -10 MeV to -28 MeV on the extent of the particles participation and the properties of the neutron star in the relativistic mean field model. We find that considering the contribution of fo and Ф mesons, the equation of state of the neutron star turns soft, the maximum mass reduces while the corresponding radius increases. Ξ- hyperons appear at lower density as UΞ^(N) becomes deeper, and the variety of UΞ^(N) has little effect on the equation of state and the properties of the neutron star.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 of Fus...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 < 109 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B > 109 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 × 106 mol/cm3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B < 109 T . But the difference will be increased with increasing SMF.展开更多
文摘Exploring the state of ultra-cold supranuclear dense matter that makes up the cores of massive neutron stars is one of the greatest unresolved problems in modern physics. In this letter, we show that when the interiors of pulsars are made of compressible and dissipative normal matter, the commonly used solution procedures combined with the known EOSs yield widely scattered solutions and poorly determined radii. A remarkable agreement emerges, however, if pulsars harbour cores that are made of incompressible entropy-free superfluids (SuSu-matter) embedded in flat spacetimes. Such supranuclear dense matter should condensate to form false vacua as predicated by non-perterbative QCD vacuum. The solutions here are found to be physically consistent and mathematically elegant, irrespective of the object’s mass. Based thereon, we conclude that the true masses of massive NSs may differ significantly from those revealed by direct observation.
基金supported by the National Natural Science Foundation of China (Grant Nos. U1938117, U1731238, 11703003, and 11647114)the International Partnership Program of Chinese Academy of Sciences (Grant No. 114A11KYSB20160008)+4 种基金the National Key Research and Development Program of China(Grant No. 2016YFA0400702)the Guizhou Provincial Science and Technology Foundation (Grant No.[2020]1Y019)the Project of Guizhou Provincial Education Department (Grant No.[2018]058)the Doctoral Project of Guizhou Education University (Grant No. 2020BS021)the Key Support Disciplines of Theoretical Physics of Department of Education of Guizhou Province,China (Grant No. ZDXK[2015]38)。
文摘So far among the nineteen pairs of detected double neutron star(DNS) systems, it is a usual fact that the first-born recycled pulsar is detected, however the youngest DNS system PSR J1906+0746, with the characteristic age of 113 kyr, is one of the three detected DNS as a non-recycled and second-born NS, which is believed to be formed by an electron capture or a low energy ultra-stripped iron core-collapse supernova(SN) explosion. The SN remnant around PSR J1906+0746 is too dim to be observed by optical telescopes, then its x-ray flux limit has been given by Chandra. A reference pulsar PSR J1509-5850 with the young characteristic age of 154 kyr was chosen as an object of comparison, which has an SN remnant observed by Chandra and is believed to be formed by iron core SN explosion. We impose a restriction on the maximum kinetic energy of electron-capture(EC) SN explosion that induces the formation of PSR J1906+0746. The estimated result is(4–8)×10^(50) erg(1 erg= 10-7 J), which is consistent with that of the published simulations of the EC process, i.e., a lower value than that of the conventional iron core SN explosion of(1–2)×10^(51) erg. As suggested, EC process for NS formation is pertained to the subluminous type Ic SN by the helium star with ONeMg core, thus for the first time we derived the kinetic energy of EC SN explosion of DNS, which may be reconciled with the recent observation of type Ic SN 2014 ft with kinetic energy of 2 × 10^(50) erg.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11988101,11773005,U2031203,U1631236,11703001,U1731238,U1938117,11725313,and 11721303)the International Partnership Program of Chinese Academy of Sciences(Grant No.114A11KYSB20160008)+1 种基金the National Key R&D Program of China(Grant No.2016YFA0400702)the Subsidy Project of the National Natural Science Foundation of China(Grant No.2021GZJ006)。
文摘LIGO-Virgo has observed the gravitational waves(GWs)from the coalescence of binary black hole(BBH)and binary neutron star(BNS)during O1 and O2,and the ones from NS-BH are expected to be hunted in the operating O3 run.The population properties and mass distribution of NS-BH mergers are poorly understood now,thus researchers simulated their chirp mass(M)distribution by a synthetic model,in which the BHs and NSs were inferred by LIGO-Virgo(O1/O2),and obtained the values in the range of 2.1 M_(⊙)<M<7.3 M_(⊙).In this paper,we further simulate the GW frequency(fGW)distribution of NS-BH mergers by the above-stated synthetic model,with a basic binary system model through the Monte Carlo method.Our results predict that the median with 90%credible intervals is 165+475-64 Hz in the case of Schwarzschild BH when the system just before merger,and this GW frequency is expected to increase several times in the merger stage,which is lying in the frequency band of LIGO-Virgo,i.e.,about 15 Hz to a few kHz.Our results provide an important reference for hunting the NS-BH mergers by the on-going O3 run of LIGO-Virgo.
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.
基金Supported by the National Program on Key Research and Development Project under Grant No 2016YFA0400801the National Natural Science Foundation of China under Grant Nos 11173034,11673023 and 11364007+2 种基金the Fundamental Research Funds for the Central Universitythe Key Support Disciplines of Theoretical Physics of Guizhou Province Education Bureau under Grant No ZDXK[2015]38the Youth Talents Project of Science and Technology in Education Bureau of Guizhou Province under Grant No KY[2017]204
文摘The aspect of formation and evolution of the recycled pulsar(PSR J0737-3039 A/B) is investigated, taking into account the contributions of accretion rate, radius and spin-evolution diagram(– diagram) in the double pulsar system. Accepting the spin-down age as a rough estimate(or often an upper limit) of the true age of the neutron star, we also impose the restrictions on the radius of this system. We calculate the radius of the recycled pulsar PSR J0737-3039 A ranges approximately from 8.14 to 25.74 km, and the composition of its neutron star nuclear matters is discussed in the mass-radius diagram.
文摘Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are embedded in Minkowski spacetime, whereas the ambient compressible and dissipative media (CDM) are imbedded in curved spacetime. As pulsars cool down, the equilibrium between both spacetime is altered, thereby triggering the well-observed glitch phenomena. Based thereon and assuming all neutron stars (<em>NSs</em>) to be born with the same initial mass of <img src="Edit_4d2d9e5f-812f-41d7-9422-5cfb3fc10997.bmp" alt="" />, we argue that the remnant of GW170817 should be a relatively faint <em>NS</em> with a massive central core made of SuSu-matter. The effective mass and radius of the remnant are predicted to be <img src="Edit_6702e3a8-abff-41f9-a45b-a2bc1e6c61b0.bmp" alt="" /> and <span style="white-space:nowrap;"><em>R</em><sub><em>rem</em></sub>=10.764 Km</span>, whereas the mass of the enclosed SuSu-core is <img src="Edit_6fe43fca-e33b-45a6-b846-bd7a09d4b8dd.bmp" alt="" />. Here, about 1/2<em>M</em><sub><em>core</em></sub> is an energy enhancement triggered by the phase transition of the gluon-quark-plasma from the microscopic into macroscopic scale. The current compactness of the remnant is <img src="Edit_38ced5f8-6f72-44d8-a3c9-89c2eaf73e0e.bmp" alt="" />, but predicted to increase as the CDM and cools down, rendering the remnant an invisible dark energy object, and therefore to an excellent black hole candidate.
基金supported,in part,by the VEGA—the Slovak Grant Agency for Science,grant No.2/0031/14by the Slovak Research and Development Agency under the contract No.APVV-0158-11.
文摘In 2011, Jun Ni published the solution of the Tolman-Oppenheimer-Volkoff equations describing the structure of stable neutron stars, which implies that 1) there is no upper mass limit of these objects, 2) their outer physical surface is always situated above the corresponding event horizon, and 3) the object is a hollow sphere with the inner physical surface and cavity inside. In our paper, we propose to “purify” the general relativity, as the geometrical theory, from the concept of mass. If we get rid of the concept of mass and Newtonian-type potential, then we obtain such the behavior of gravity which results in the above mentioned stable Ni’s object. It is farther pointed out that the distribution of matter, which is observed as spherically symmetric by the observer in its center, is not longer observed as spherically symmetric by an observer aside the center in a curved spacetime of general relativity. This fact implies, in contrast to the Newtonian physics, the non-zero and outward oriented gravitational attraction of upper layers of star. Ni considered positive energy density and pressure. In addition, gravity had everywhere attractive character. No “exotic” assumption was made. Hence, there is no reason why his concept of hollow sphere should not be applicable to the models of real objects.
基金Supported by the National Natural Science Foundation of China(Grant Nos.10603002 and 10773004)
文摘In a second-order r-mode theory,Sa' and Tome' found that the r-mode oscillation in neutron stars(NSs) could induce stellar differential rotation,which naturally leads to a saturated state of the oscillation.Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution,we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries,where the viscous damping of the r-modes and its resultant effects are taken into account.The numerical results show that,for both kinds of NSs,the differential rotation can significantly prolong the duration of the r-modes.As a result,the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years.Moreover,the persistent radiation of a quasi-monochromaticgravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation.This increases the detectability of gravitational waves from both young isolated and old accreting NSs.
基金Supported by National Natural Science Foundation of China(Nos.10947023,11275073 and 11205061)Fundamental Research Funds for the Central University,China(No.2012ZZ0079)sponsored by SRF for ROCS,SEM
文摘The eigen-frequencies of the axial w-modes of neutron star described by a super-soft equation of state(EOS) are investigated,by considering the non-Newtonian gravity.The results show that at the same stellar mass,the frequencies of wI and wI2 for our model are lower than that of the typical EOSs(such as APR); and the frequencies increase with the stellar masses,which is contrary to that of the typical EOSs.These characters may provide a probe to testify the super soft symmetry energy and the non-Newtonian gravity in the future.Moreover,our model also has the universal behavior of the mass-scaled eigen-frequencies as a function of the compactness.
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.G2000-0774-07
the 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 Natural Science Foundation of China (Grant Nos. 11273020, 11305133 and U1331121)China Scholarship (Grant No. 2011851096)the Science Foundation of China West Normal University (Grant No. 11B007)
文摘When a daughter nucleus produced by electron capture takes part in a level transition from an excited state to its ground state in accreting neutron star crusts, thermal energy will be released and heat the crust, increasing crust temperature and changing subsequent carbon ignition conditions. Previous studies show that the theoretical carbon ignition depth is deeper than the value inferred from observations because the thermal energy is not sufficient. In this paper, we present the de-excited energy from electron capture of rp-process ash before carbon ignition, especially for the initial evolution stage of rp-process ash, by using a level-to-level transition method. We find the theoretical column density of carbon ignition in the resulting superbursts and compare it with observations. The calculation of the electron capture process is based on a more reliable level-to-level transition, adopting new data from experiments or theoretical models(e.g., large-scale shell model and proton-neutron quasi-particle random phase approximation). The new carbon ignition depth is estimated by fitting from previous results of a nuclear reaction network. Our results show the average de-excited energy from electron capture before carbon ignition is ~0.026 Me V/u, which is significantly larger than the previous results. This energy is beneficial for enhancing the crust’s temperature and decreasing the carbon ignition depth of superbursts.
基金supported by the Ministry of Education and Sciences of the Republic of Armenia under grant 2008-130
文摘The deconfinement phase transition from hadronic matter to quark matter in the interior of compact stars is investigated. The hadronic phase is described in the framework of relativistic mean-field theory, where the scalar-isovector δ-meson effective field is also taken into account. The MIT bag model for describing a quark phase is used. The changes of the parameters of phase transition caused by the presence of a δ-meson field are explored. Finally, alterations in the integral and structural parameters of hybrid stars due to both a deconfinement phase transition and inclusion of a δ-meson field are discussed.
文摘We review theoretical relations between macroscopic properties of neutron stars and microscopic quantities of nuclear matter, such as consistency of hadronic nuclear models and observed masses of neutron stars. The relativistic hadronic field theory, quantum hadrodynamics (QHD), and mean-field approximations of the theory are applied to saturation properties of symmetric nuclear and neutron matter. The equivalence between mean-field approximations and Hartree approximation is emphasized in terms of renormalized effective masses and effective coupling constants of hadrons. This is important to prove that the direct application of mean-field (Hartree) approximation to nuclear and neutron matter is inadequate to examine physical observables. The equations of state (EOS), binding energies of nuclear matter, self-consistency of nuclear matter, are reviewed, and the result of chiral Hartree-Fock ?approximation is shown. Neutron stars and history of nuclear astrophysics, nuclear model and nuclear matter, possibility of hadron and hadron-quark neutron stars are briefly reviewed. The hadronic models are very useful and practical for understanding astrophysical phenomena, nuclear matter and radiation phenomena of nuclei.
基金supported by theNational Key Research and Development Program ofChina (2016YFA0400803)the National Natural Science Foundation of China (NSFC) (Grant Nos. 11333004,11773015 and 11573016)+1 种基金Project U1838201 supported by NSFC and CASthe Program for Innovative Research Team (in Science and Technology) at the University of Henan Province
文摘We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.
基金Supported by the National Natural Science Foundation of China
文摘Resonant cyclotron scattering(RCS) in pulsar magnetospheres is considered.The photon diffusion equation(Kompaneets equation) for RCS is derived.The photon system is modeled three dimensionally.Numerical calculations show that there exist not only up scattering but also down scattering of RCS,depending on the parameter space.RCS's possible applications to spectral energy distributions of magnetar candidates and radio quiet isolated neutron stars(INSs) are pointed out.The optical/UV excess of INSs may be caused by the down scattering of RCS.The calculations for RX J1856.5-3754 and RX J0720.4-3125 are presented and compared with their observational data.In our model,the INSs are proposed to be normal neutron stars,although the quark star hypothesis is still possible.The low pulsation amplitude of INSs is a natural consequence in the RCS model.
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 constrained 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 w I -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Supported in part by National Natural Science Foundation of China under Grant Nos.10275029 and 10675054
文摘In the framework of relativistic mean field theory,the condensations of K^- and (?)~0 in neutron star matterincluding baryon octet and Δ quartet are studied.We find that in this case K^- and (?)~0 condensations can occur atrelative shallow optical potential depth of (?) from -80 MeV to -160 MeV.Both K^- and (?)~0 condensations favor theappearances of Δ resonances.With (?) condensations all the Δ quartet can appear well inside the maximum mass stars.The appearances of Δ resonances change the composition and distribution of particles at high densities.The populationsof Δ resonances can enhance K^- condensation.It is found that in the core of massive neutron stars,neutron star matterincludes rich particle species,such as antikaons,baryon octet,and Δ quartet.In the presence of Δ resonances and (?)condensation,the EOS becomes softer and results in smaller maximum mass stars.Furthermore the impact of antikaoncondensations,hyperons,and Δ resonances on direct Urca process with nucleons is also discussed briefly.
基金The project supported in part by the Postdoctoral Science Foundation of China under Grant No.2002032169+2 种基金
National Natural Science Foundation of China under Grant No.10275037
the Foundation for Doctorate Training Program of China under Grant No.2001005
文摘We examine the effect of adding mesons fo(975) and Ф(1020) as well as the variety of UΞ^(N) (the potential well depth ofΞ in nuclear matter) from -10 MeV to -28 MeV on the extent of the particles participation and the properties of the neutron star in the relativistic mean field model. We find that considering the contribution of fo and Ф mesons, the equation of state of the neutron star turns soft, the maximum mass reduces while the corresponding radius increases. Ξ- hyperons appear at lower density as UΞ^(N) becomes deeper, and the variety of UΞ^(N) has little effect on the equation of state and the properties of the neutron star.
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 < 109 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B > 109 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 × 106 mol/cm3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B < 109 T . But the difference will be increased with increasing SMF.
