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Investigating the neutron star physics through observations of several young pulsars in the dipole-field re-emergence scenario

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Science China(Physics,Mechanics & Astronomy) 2024年

作者： Yu-Long Yan Quan Cheng xiao-ping zheng Institute of Astrophysics Central China Normal University Department of Astronomy Huazhong University of Science and Technology

The observed timing data, magnetic tilt angle χ, and age of young pulsars could be used to probe some important issues about neutron star（NS） physics, e.g., the NS internal magnetic field configuration, and the number of precession cycles ξ. Both quantities are critical in studying the continuous gravitational wave emission from pulsars, and the latter generally characterizes the mutual interactions between superfluid neutrons and other particles in the NS interior. The timing behavior of pulsars can be influenced by the dipole field evolution, which instead of decaying, may increase with time. An increase in the dipole field may result from the re-emergence of the initial dipole field Bd,ithat was buried into the NS interior shortly after the birth of the *** this work, the field re-emergence scenario ξ and the internal field configuration of several young pulsars, as well as their Bd,iare investigated by assuming typical accreted masses △M. Moreover, since the Crab pulsar has an exactly known age and its tilt angle change rate can be inferred from observations, we can set stringent constraints on its ξ, Bd,i, and △M. Although for other young pulsars without exactly known ages and tilt angle change rates, these quantities cannot be accurately determined, we find that their ξ are generally within ～10～4-10～6, and some of them probably have magnetar-strength Bd,i. Our work could be important for investigating the transient emissions associated with NSs, the origin of strong magnetic fields of NSs, pulsar population,continuous gravitational wave emission from pulsars, and accretion under extreme conditions in principle.

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Observational Constraints on Quark Matter in Neutron Stars

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Chinese Journal of Astronomy and Astrophysics 2007年第5期7卷 675-684页

作者： Na-Na Pan xiao-ping zheng Institute of Astrophysics Huazhong Normal University Wuhan 430079

We study the observational constraints of mass and redshift on the properties of the equation of state （EOS） for quark matter in compact stars based on the quasi-particle description. We discuss two scenarios; strange stars and hybrid stars. We construct the equations of state utilizing an extended MIT bag model taking the medium effect into account for quark matter and the relativistic mean field theory for hadron matter. We show that quark matter may exist in strange stars and in the interior of neutron stars. The bag constant is a key parameter that affects strongly the mass of strange stars. The medium effect can lead to the stiffer hybrid-star EOS approaching the pure hadronic EOS, due to the reduction of quark matter, and hence the existence of heavy hybrid stars. We find that a middle range coupling constant may be the best choice for the hybrid stars being compatible with the observational constraints.

关键词： dense matter -- gravitation -- stars neutron -- stars rotation -- stars oscillations

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Quark stars with strong magnetic fields: considering different magnetic field geometries

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Research in Astronomy and Astrophysics 2017年第10期17卷 27-32页

作者： Wei Wei Xi-Wei Liu xiao-ping zheng College of Science Huazhong Agricultural University College of Physical Science and Technology Central China Normal University

We calculate the mass-radius relationship of quark stars with the magnetized density- dependent quark mass model in this work, considering two magnetic field geometries： a statistically isotropic, tangled field and a force-free configuration. In both cases, magnetic field production decreases in the case of maximum quark star mass. Furthermore, a tangled, isotropic magnetic field has a relatively smaller impact on the mass and radius, compared to the force-free configuration, which implies that the geometry of the interior magnetic field is at least as important as the field strength itself when the influ- ence of the strong magnetic field on the mass and radius is assessed.

关键词： stars: neutron -- equation of state -- magnetic fields

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A possible origin of the Galactic Center magnetar SGR 1745–2900

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Research in Astronomy and Astrophysics 2017年第6期17卷 47-54页

作者： Quan Cheng Shuang-Nan Zhang xiao-ping zheng Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of Sciences Institute of Astrophysics Central China Normal University

Since there is a large population of massive O/B stars and putative neutron stars （NSs） located in the vicinity of the Galactic Center （GC）, intermediate-mass X-ray binaries （IMXBs） constituted by an NS and a B-type star probably exist there. We investigate the evolutions of accreting NSs in IMXBs （similar to M82 X-2） with a - 5.2 M companion and orbital period 2.53 d. By adopting a mildly super-Eddington rate M = 6 × 10-8 M yr-1 for the early Case B Roche-lobe overflow （RLOF） accretion, we find that only in accreting NSs with quite elastic crusts （slippage factor s = 0.05） can the toroidal magnetic fields be amplified within 1 Myr, which is assumed to be the longest duration of the RLOF. These IMXBs will evolve into NS＋white dwarf （WD） binaries if they are dynamically stable. However, before the formation of NS＋WD binaries, the high stellar density in the GC will probably lead to frequent encounters between the NS＋evolved star binaries （in post-early Case B mass transfer phase） and NSs or exchange encounters with other stars, which may produce single NSs. These NSs will evolve into magnetars when the amplified poloidal magnetic fields diffuse out to the NS surfaces. Consequently, our results provide a possible expianation for the origin of the GC magnetar SGR 1745-2900. Moreover, the accreting NSs with s 〉 0.05 will evolve into millisecond pulsars （MSPs）. Therefore, our model reveals that the GC magnetars and MSPs could both originate from a special kind of IMXB.

关键词： stars neutron - stars magnetars - stars magnetic field - pulsars individual (SGR1745-2900)

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Thermal evolution of neutron stars with decaying magnetic fields

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Research in Astronomy and Astrophysics 2015年第9期15卷 1475-1482页

作者： Wei Wei xiao-ping zheng Xi-Wei Liu College of Science Huazhong Agricultural University College of Physical Science and Technology Central China Normal University

Rotochemical heating originates in the deviation from beta equilibrium due to spin-down compression, which is closely related to the dipole magnetic field. We numerically calculate the deviation from chemical equilibrium and thermal evolution of neutron stars with decaying magnetic fields. We find that the power-law long term decay of the magnetic field slightly affects the deviation from chemical equilibrium and surface temperature. However, the magnetic decay leads to older neutron stars that could have a different surface temperature with the same magnetic field strength. That is, older neutron stars with a low magnetic field （10^8 G） could have a lower temper- ature even with rotochemical heating in operation, which probably explains the lack of other observations on older millisecond pulsars with higher surface temperature, except millisecond pulsar J0437-4715.

关键词： stars: neutron -- stars: magnetic field -- radiation mechanisms: thermal

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Long-term evolution and gravitational wave radiation of neutron stars with differential rotation induced by r-modes

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Research in Astronomy and Astrophysics 2009年第9期9卷 1024-1034页

作者： Yun-Wei Yu xiao-Feng Cao xiao-ping zheng Institute of Astrophysics Huazhong Normal University Wuhan 430079 China

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-monochromatic gravitational 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.

关键词： stars: neutron -- stars: evolution -- stars: rotation -- gravitational waves

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R-mode instability of strange stars and observations of neutron stars in LMXBs

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Research in Astronomy and Astrophysics 2015年第6期15卷 871-878页

作者： Chun-Mei Pi Shu-Hua Yang xiao-ping zheng Department of Physics and Engineering Hubei University of Education Institute of Astrophysics Central China Normal University

Using a realistic equation of state （EOS） of strange quark matter, namely, the modified bag model, and considering the constraints on the parameters of EOS by the observational mass limit of neutron stars, we investigate the r-mode instability window of strange stars, and find the same result as in the brief study of Haskell, Degenaar and Ho in 2012 that these instability windows are not consistent with the spin frequency and temperature observations of neutron stars in low mass X-ray binaries.

关键词： dense matter -- stars: neutron -- stars: oscillations

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Effect of time interval on microstructure evolution of medium carbon steel during warm deformation

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Journal of Iron and Steel Research International 2019年第6期26卷 602-610页

作者： Hong-bin Li xiao-ping zheng De-cheng Wan Lian-sheng Chen College of Metallurgy and Energy North China University of Science and Technology Tangshan 063009 Hebei China Modem Metallurgy of Hebei Province Key Laboratory Tangshan 063009 Hebei China

The thermal mechanical simulator system (Gleeble-3500) was used to carry out the double passes compression tests. The microstructure evolution of medium carbon steel with different time intervals during warm deformation was investigated by scanning electron microscopy, transmission electron microscopy and electron back-scattered diffraction. The results show that the effects of time interval on microstructure evolution are very important. The low-angle boundaries transform into high-angle boundaries (HABs) during interval. The fraction of HABs and homogeneity of particle carbides increase with increasing time interval. In addition, the homogeneity of carbides also increases with the strain. However, the effects of time interval on the microstructure evolution are negligible when it exceeds 100 s.

关键词： Double-pass deformation Warm deformation Microstructure evolution Misorientation

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First-order phase transitions in rotating hybrid stars and pulsar glitches

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Research in Astronomy and Astrophysics 2011年第6期11卷 679-686页

作者： Fei xiao Chun-Mei Shu-Hua Yang Ai-Zhi Zhou xiao-ping zheng Department of Physics and Electronics Hubei University of Education Wuhan 430205 China Institute of Astrophysics Huazhong Normal University Wuhan 430079 China

The first order deconfinement phase transitions in rotating hybrid stars are studied and it is found that if the surface tension is sufficiently large, the transition from metastable hadron matter to stable mixed hadr... 详细信息

关键词： dense matter-stars: rotation-pulsars: general

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Contrast-enhanced ultrasound predicts microvascular invasion in patients with hepatocellular carcinoma

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Hepatobiliary & Pancreatic Diseases International 2022年第6期21卷 609-613页

作者： Jing-Yuan Huang Zhi-Liang Huang Zhe Yang xiao-ping zheng Department of Ultrasound Shulan(Hangzhou)Hospital Affiliated to Zhejiang Shuren University Shulan International Medical CollegeHangzhou 310022China Department of Hepatobiliary and Pancreatic Surgery Shulan(Hangzhou)Hospital Affiliated to Zhejiang Shuren University Shulan International Medical CollegeHangzhou 310022China Department of Pathology Shulan(Hangzhou)Hospital Affiliated to Zhejiang Shuren University Shulan International Medical CollegeHangzhou 310022China

To the Editor:The presence of microvascular invasion(MVI)in hepatocellular carcinoma(HCC)is an important indicator for HCC recurrence and poor prognosis[1].Determining the preoperative MVI status is helpful for guiding clinical treatment and improving ***,MVI diagnosis is achieved primarily by postoperative histopathology,which makes it difficult to provide a definite diagnosis before ***,significant advancements in imaging technology have begun to allow clinicians to make a diagnosis of HCC MVI prior to *** this study,we used contrast-enhanced ultrasound(CEUS)to observe the characteristics of HCC enhancement patterns and quantitatively analyze the changes in HCC blood perfusion parameters to explore the value of CEUS in evaluating HCC MVI.

关键词： invasion diagnosis hepatocellular

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