In this work,we perform a Bayesian inference of the crust-core transition density ρ_(t) of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method.Uniform and Gau...In this work,we perform a Bayesian inference of the crust-core transition density ρ_(t) of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method.Uniform and Gaussian distributions for the ρ_(t) prior were adopted in the Bayesian approach.It has a larger probability of having values higher than 0.1 fm^(−3) for ρ_(t) as the uniform prior and neutron-star radius data were used.This was found to be controlled by the curvature K_(sym) of the nuclear symmetry energy.This phenomenon did not occur if K_(sym) was not extremely negative,namely,K_(sym)>−200 MeV.The value ofρ_(t) obtained was 0.075_(−0.01)^(+0.005) fm^(−3) at a confidence level of 68%when both the neutron-star radius and neutron-skin thickness data were considered.Strong anti-correlations were observed between ρ_(t),slope L,and curvature of the nuclear symmetry energy.The dependence of the three L-K_(sym) correlations predicted in the literature on crust-core density and pressure was quantitatively investigated.The most probable value of 0.08 fm^(−3) for ρ_(t) was obtained from the L-K_(sym) relationship proposed by Holt et al.while larger values were preferred for the other two relationships.展开更多
In accreting neutron star (NS) low-mass X-ray binaries (LMXBs), the turbulent flow in accretion disk may show magnetic structures. Its emission will vary in time due to inhomogeneous motions through and with the accre...In accreting neutron star (NS) low-mass X-ray binaries (LMXBs), the turbulent flow in accretion disk may show magnetic structures. Its emission will vary in time due to inhomogeneous motions through and with the accretion flow. These emissions contribute to considerable X-ray variability on a wide range of timescales in all wavelengths, and down to milliseconds. In this article, we give a brief review for quasi-periodic oscillations (QPOs), one of a periodic X-ray variability, in NS/ LMXBs. Firstly, we give a brief introduction to NS/LMXBs and the fruitful QPO components. As an example, the energy dependence of normal branch oscillations in Scorpius X-1 is discussed. We mostly focus on the properties and mechanism of kilohertz QPOs—the fastest variability components that have the same order as the dynamical timescales of the innermost regions of accretion flow. Finally, we discuss the success and questions for theoretical interpretations and present the possible entry for investigation of nature of QPOs.展开更多
随着天文观测数据日益增多,通过数据驱动的方法推断中子星物质的状态方程成为一种可行的方案。本文采用贝叶斯推断和天体物理观测约束相对论平均场(Relativistic Mean Field,RMF)模型,并以此为基础,研究了核状态方程(Equation of State,...随着天文观测数据日益增多,通过数据驱动的方法推断中子星物质的状态方程成为一种可行的方案。本文采用贝叶斯推断和天体物理观测约束相对论平均场(Relativistic Mean Field,RMF)模型,并以此为基础,研究了核状态方程(Equation of State,EOS)和中子星结构。通过分析不同交点密度下与耦合常数密度依赖行为,发现较高的交点密度加强了天体物理观测数据对物态方程的约束,导致大质量中子星的中等密度行为变软,中心能量密度增加。特别地,我们发现包括在大质量中子星核中,声速平方超过共形极限(v_(s)^(2)>1/3)的概率很高。推断的最大中子星质量(M_(max)≥2.5 M⊙)与引力波事件(如GW190814)的解释一致,即其小质量伴星很可能对应于大质量中子星。此外,极端密度下的对称能和压强也表现出交点密度依赖性,符合多信使约束。展开更多
The central compact object XMMU J173203.3-344518 in the supernova remnant HESS J1731-347 challenges conventional neutron star models due to its low mass M=0.77_(-0.17)^(+0.20)M■and high redshifted surface temperature...The central compact object XMMU J173203.3-344518 in the supernova remnant HESS J1731-347 challenges conventional neutron star models due to its low mass M=0.77_(-0.17)^(+0.20)M■and high redshifted surface temperature T_(s)^(∞)=156_(-6)^(+6)e V (1.81_(-0.07)^(+0.07)×10^(6)K).We investigate the observational properties of XMMU J173203.3-344518 within a color-flavor-locked(CFL) phase strange star model.We construct a thermal evolution model of the CFL phase strange star,along with heating due to the viscous dissipation of r-mode oscillations.Employing one of th most widely used quark matter equations of state,we characterize the star properties by the strange quark mas(ms),effective bag constant (Beff),perturbative QCD correction (a4),and pairing gap (Δ).Our analysi demonstrates that the observed properties of XMMU J173203.3344518 can be explained by r-mode heating with CFL strange star,provided that the initial spin period is shorter than 18 ms.We constrain the r-mode saturation amplitude to 8×10^(-3)–1.4×10^(-2)and predict a current spin period of 6–9 ms for an initial period of 1 ms.Thi rapid rotation is consistent with the absence of detected pulsations.The r-mode instability window remains robus across a wide range of pairing gap values (5–200 MeV),providing a reliable framework for interpretation regardless of microscopic uncertainties.Our results support the identification of XMMU J173203.3344518 as rapidly rotating,low-mass CFL phase strange star,demonstrating the importance of r-mode heating in the therma evolution of compact objects with exotic dense matter.展开更多
Short-duration gamma-ray bursts (SGRBs) are mysterious gamma-ray flashes with durations less than two seconds, which occur at the cosmological distances. Some of them usually not only have very tenuous medium gases an...Short-duration gamma-ray bursts (SGRBs) are mysterious gamma-ray flashes with durations less than two seconds, which occur at the cosmological distances. Some of them usually not only have very tenuous medium gases and old host galaxies but also are in the outskirts of the galaxies, suggesting an origin of binary neutron star (NS) mergers (1)This origin was confirmed undoubtedly thanks to the discoveries of a gravitational wave event namedGW170817 and its electromagnetic counterparts (an SGRB, a multiwavelengthkilo-nova, and a broadband afterglow) [2].展开更多
With the support by the National Natural Science Foundation of China and other grants,the research team led by Prof.Xue YongQuan(薛永泉)at the Department of Astronomy,University of Science and Technology of China,disc...With the support by the National Natural Science Foundation of China and other grants,the research team led by Prof.Xue YongQuan(薛永泉)at the Department of Astronomy,University of Science and Technology of China,discovered the first X-ray transient that was powered by a magnetar formed during a binary neutron-star merger,which was published in Nature(2019,568:198—201).展开更多
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
In this paper, we show that massive envelopes made of highly compressed normal matter surrounding dark objects (DEOs) can curve the surrounding spacetime and make the systems observationally indistinguishable from the...In this paper, we show that massive envelopes made of highly compressed normal matter surrounding dark objects (DEOs) can curve the surrounding spacetime and make the systems observationally indistinguishable from their massive black hole counterparts. DEOs are new astrophysical objects that are made up of entropy-free incompressible supranuclear dense superfluid (SuSu-matter), embedded in flat spacetimes and invisible to outside observers, practically trapped in false vacua. Based on highly accurate numerical modelling of the internal structures of pulsars and massive neutron stars, and in combination with using a large variety of EOSs, we show that the mass range of DEOs is practically unbounded from above: it spans those of massive neutron stars, stellar and even supermassive black holes: thanks to the universal maximum density of normal matter, , beyond which normal matter converts into SuSu-matter. We apply the scenario to the Crab and Vela pulsars, the massive magnetar PSR J0740 6620, the presumably massive NS formed in GW170817, and the SMBHs in Sgr A* and M87*. Our numerical results also reveal that DEO-Envelope systems not only mimic massive BHs nicely but also indicate that massive DEOs can hide vast amounts of matter capable of turning our universe into a SuSu-matter-dominated one, essentially trapped in false vacua.展开更多
Supermassive DEOs (SMDEOs) are cosmologically evolved objects made of irreducible incompressible supranuclear dense superfluids: The state we consider to govern the matter inside the cores of massive neutron stars. Th...Supermassive DEOs (SMDEOs) are cosmologically evolved objects made of irreducible incompressible supranuclear dense superfluids: The state we consider to govern the matter inside the cores of massive neutron stars. These cores are practically trapped in false vacua, rendering their detection by outside observers impossible. Based on massive parallel computations and theoretical investigations, we show that SMDEOs at the centres of spiral galaxies that are surrounded by massive rotating torii of normal matter may serve as powerful sources for gravitational waves carrying away roughly 1042 erg/s. Due to the extensive cooling by GWs, the SMDEO-Torus systems undergo glitching, through which both rotational and gravitational energies are abruptly ejected into the ambient media, during which the topologies of the embedding spacetimes change from curved into flatter ones, thereby triggering a burst gravitational energy of order 1059 erg. Also, the effects of glitches found to alter the force balance of objects in the Lagrangian-L1 region between the central SMDEO-Torus system and the bulge, enforcing the enclosed objects to develop violent motions, that may explain the origin of the rotational curve irregularities observed in the innermost part of spiral galaxies. Our study shows that the generated GWs at the centres of galaxies, which traverse billions of objects during their outward propagations throughout the entire galaxy, lose energy due to repeatedly squeezing and stretching the objects. Here, we find that these interactions may serve as damping processes that give rise to the formation of collective forces f∝m(r)/r, that point outward, endowing the objects with the observed flat rotation curves. Our approach predicts a correlation between the baryonic mass and the rotation velocities in galaxies, which is in line with the Tully-Fisher relation. The here-presented self-consistent approach explains nicely the observed rotation curves without invoking dark matter or modifying Newtonian gravitation in the low-field approximation.展开更多
基金supported by the Shanxi Provincial Foundation for Returned Overseas Scholars (No. 20220037)Natural Science Foundation of Shanxi Province (No. 20210302123085)Discipline Construction Project of Yuncheng University
文摘In this work,we perform a Bayesian inference of the crust-core transition density ρ_(t) of neutron stars based on the neutron-star radius and neutron-skin thickness data using a thermodynamical method.Uniform and Gaussian distributions for the ρ_(t) prior were adopted in the Bayesian approach.It has a larger probability of having values higher than 0.1 fm^(−3) for ρ_(t) as the uniform prior and neutron-star radius data were used.This was found to be controlled by the curvature K_(sym) of the nuclear symmetry energy.This phenomenon did not occur if K_(sym) was not extremely negative,namely,K_(sym)>−200 MeV.The value ofρ_(t) obtained was 0.075_(−0.01)^(+0.005) fm^(−3) at a confidence level of 68%when both the neutron-star radius and neutron-skin thickness data were considered.Strong anti-correlations were observed between ρ_(t),slope L,and curvature of the nuclear symmetry energy.The dependence of the three L-K_(sym) correlations predicted in the literature on crust-core density and pressure was quantitatively investigated.The most probable value of 0.08 fm^(−3) for ρ_(t) was obtained from the L-K_(sym) relationship proposed by Holt et al.while larger values were preferred for the other two relationships.
文摘In accreting neutron star (NS) low-mass X-ray binaries (LMXBs), the turbulent flow in accretion disk may show magnetic structures. Its emission will vary in time due to inhomogeneous motions through and with the accretion flow. These emissions contribute to considerable X-ray variability on a wide range of timescales in all wavelengths, and down to milliseconds. In this article, we give a brief review for quasi-periodic oscillations (QPOs), one of a periodic X-ray variability, in NS/ LMXBs. Firstly, we give a brief introduction to NS/LMXBs and the fruitful QPO components. As an example, the energy dependence of normal branch oscillations in Scorpius X-1 is discussed. We mostly focus on the properties and mechanism of kilohertz QPOs—the fastest variability components that have the same order as the dynamical timescales of the innermost regions of accretion flow. Finally, we discuss the success and questions for theoretical interpretations and present the possible entry for investigation of nature of QPOs.
文摘随着天文观测数据日益增多,通过数据驱动的方法推断中子星物质的状态方程成为一种可行的方案。本文采用贝叶斯推断和天体物理观测约束相对论平均场(Relativistic Mean Field,RMF)模型,并以此为基础,研究了核状态方程(Equation of State,EOS)和中子星结构。通过分析不同交点密度下与耦合常数密度依赖行为,发现较高的交点密度加强了天体物理观测数据对物态方程的约束,导致大质量中子星的中等密度行为变软,中心能量密度增加。特别地,我们发现包括在大质量中子星核中,声速平方超过共形极限(v_(s)^(2)>1/3)的概率很高。推断的最大中子星质量(M_(max)≥2.5 M⊙)与引力波事件(如GW190814)的解释一致,即其小质量伴星很可能对应于大质量中子星。此外,极端密度下的对称能和压强也表现出交点密度依赖性,符合多信使约束。
基金supported in part by the Natural Science Foundation of Xinjiang Uygur Autonomous Region (No.2023D01E20)the National Key R&D Program of China (No.2022YFA1603104)+3 种基金the National Natural Science Foundation of China (Nos.12288102,12273028 and 12033001)the Tianshan talents program (2023TSYCTD0013)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region (No.2022A03013-1)the Urumqi Nanshan Astronomy and Deep Space Exploration Observation and Research Station of Xinjiang (XJYWZ2303)。
文摘The central compact object XMMU J173203.3-344518 in the supernova remnant HESS J1731-347 challenges conventional neutron star models due to its low mass M=0.77_(-0.17)^(+0.20)M■and high redshifted surface temperature T_(s)^(∞)=156_(-6)^(+6)e V (1.81_(-0.07)^(+0.07)×10^(6)K).We investigate the observational properties of XMMU J173203.3-344518 within a color-flavor-locked(CFL) phase strange star model.We construct a thermal evolution model of the CFL phase strange star,along with heating due to the viscous dissipation of r-mode oscillations.Employing one of th most widely used quark matter equations of state,we characterize the star properties by the strange quark mas(ms),effective bag constant (Beff),perturbative QCD correction (a4),and pairing gap (Δ).Our analysi demonstrates that the observed properties of XMMU J173203.3344518 can be explained by r-mode heating with CFL strange star,provided that the initial spin period is shorter than 18 ms.We constrain the r-mode saturation amplitude to 8×10^(-3)–1.4×10^(-2)and predict a current spin period of 6–9 ms for an initial period of 1 ms.Thi rapid rotation is consistent with the absence of detected pulsations.The r-mode instability window remains robus across a wide range of pairing gap values (5–200 MeV),providing a reliable framework for interpretation regardless of microscopic uncertainties.Our results support the identification of XMMU J173203.3344518 as rapidly rotating,low-mass CFL phase strange star,demonstrating the importance of r-mode heating in the therma evolution of compact objects with exotic dense matter.
文摘Short-duration gamma-ray bursts (SGRBs) are mysterious gamma-ray flashes with durations less than two seconds, which occur at the cosmological distances. Some of them usually not only have very tenuous medium gases and old host galaxies but also are in the outskirts of the galaxies, suggesting an origin of binary neutron star (NS) mergers (1)This origin was confirmed undoubtedly thanks to the discoveries of a gravitational wave event namedGW170817 and its electromagnetic counterparts (an SGRB, a multiwavelengthkilo-nova, and a broadband afterglow) [2].
文摘With the support by the National Natural Science Foundation of China and other grants,the research team led by Prof.Xue YongQuan(薛永泉)at the Department of Astronomy,University of Science and Technology of China,discovered the first X-ray transient that was powered by a magnetar formed during a binary neutron-star merger,which was published in Nature(2019,568:198—201).
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.
文摘In this paper, we show that massive envelopes made of highly compressed normal matter surrounding dark objects (DEOs) can curve the surrounding spacetime and make the systems observationally indistinguishable from their massive black hole counterparts. DEOs are new astrophysical objects that are made up of entropy-free incompressible supranuclear dense superfluid (SuSu-matter), embedded in flat spacetimes and invisible to outside observers, practically trapped in false vacua. Based on highly accurate numerical modelling of the internal structures of pulsars and massive neutron stars, and in combination with using a large variety of EOSs, we show that the mass range of DEOs is practically unbounded from above: it spans those of massive neutron stars, stellar and even supermassive black holes: thanks to the universal maximum density of normal matter, , beyond which normal matter converts into SuSu-matter. We apply the scenario to the Crab and Vela pulsars, the massive magnetar PSR J0740 6620, the presumably massive NS formed in GW170817, and the SMBHs in Sgr A* and M87*. Our numerical results also reveal that DEO-Envelope systems not only mimic massive BHs nicely but also indicate that massive DEOs can hide vast amounts of matter capable of turning our universe into a SuSu-matter-dominated one, essentially trapped in false vacua.
文摘Supermassive DEOs (SMDEOs) are cosmologically evolved objects made of irreducible incompressible supranuclear dense superfluids: The state we consider to govern the matter inside the cores of massive neutron stars. These cores are practically trapped in false vacua, rendering their detection by outside observers impossible. Based on massive parallel computations and theoretical investigations, we show that SMDEOs at the centres of spiral galaxies that are surrounded by massive rotating torii of normal matter may serve as powerful sources for gravitational waves carrying away roughly 1042 erg/s. Due to the extensive cooling by GWs, the SMDEO-Torus systems undergo glitching, through which both rotational and gravitational energies are abruptly ejected into the ambient media, during which the topologies of the embedding spacetimes change from curved into flatter ones, thereby triggering a burst gravitational energy of order 1059 erg. Also, the effects of glitches found to alter the force balance of objects in the Lagrangian-L1 region between the central SMDEO-Torus system and the bulge, enforcing the enclosed objects to develop violent motions, that may explain the origin of the rotational curve irregularities observed in the innermost part of spiral galaxies. Our study shows that the generated GWs at the centres of galaxies, which traverse billions of objects during their outward propagations throughout the entire galaxy, lose energy due to repeatedly squeezing and stretching the objects. Here, we find that these interactions may serve as damping processes that give rise to the formation of collective forces f∝m(r)/r, that point outward, endowing the objects with the observed flat rotation curves. Our approach predicts a correlation between the baryonic mass and the rotation velocities in galaxies, which is in line with the Tully-Fisher relation. The here-presented self-consistent approach explains nicely the observed rotation curves without invoking dark matter or modifying Newtonian gravitation in the low-field approximation.
