A5081963183- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Particle accelerators and beam dynamics
- Gamma-ray bursts and supernovae
- High-pressure geophysics and materials
- Seismic Waves and Analysis
- Atomic and Subatomic Physics Research
- Stellar, planetary, and galactic studies
- Radio Astronomy Observations and Technology
- Particle Accelerators and Free-Electron Lasers
- Physics of Superconductivity and Magnetism
- Cosmology and Gravitation Theories
- Global Education and Multiculturalism
- Superconducting Materials and Applications
- Geomagnetism and Paleomagnetism Studies
- Global Educational Policies and Reforms
- Astrophysics and Cosmic Phenomena
- Seismology and Earthquake Studies
- Geophysics and Sensor Technology
- Gyrotron and Vacuum Electronics Research
- GNSS positioning and interference
- Adaptive optics and wavefront sensing
- Astronomy and Astrophysical Research
- Advanced Frequency and Time Standards
Purple Mountain Observatory
2025
Jimei University
2018-2023
Huazhong University of Science and Technology
2007-2022
National Astronomical Observatories
2012-2019
University of Chinese Academy of Sciences
2013-2016
Chinese Academy of Sciences
2012-2015
Cornell University
2009-2013
Shanxi Normal University
2007-2009
Nanchang University
2008
Princeton University
1992
Recent observations and theoretical work on gamma-ray bursts favor the central engine model of a Kerr black hole (BH) surrounded by magnetized neutrino-dominated accretion flow (NDAF). The magnetic coupling between BH disk through large-scale closed field exerts torque transports rotational energy from to disk. We investigate properties NDAF with this torque. For rapid spinning BH, transfers enormous into inner There are two consequences: (1) luminosity neutrino annihilation is greatly...
Objective To describe the clinical features, treatment, and prognostic factors affecting recurrence long-term adverse outcomes of myelin oligodendrocyte antibody-associated disease (MOGAD). Methods In this retrospective cohort study, records patients diagnosed with MOGAD at Zhengzhou University First Affiliated Hospital between January 2018 March 2023 were analyzed, associated poor prognosis identified using logistic regression. Results Of 91 patients, 69 (76%) new cases, 39 (43%) female, 47...
The opening of the gravitational wave window has significantly enhanced our capacity to explore universe's most extreme and dynamic sector. In mHz frequency range, a diverse range compact objects, from massive black holes at farthest reaches Universe lightest white dwarfs in cosmic backyard, generate complex symphony signals. Once recorded by detectors, these unique fingerprints have potential decipher birth growth structures over wide scales, stellar binaries clusters galaxies large-scale...
Here we report that the observed braking indices of 366 pulsars in sample Hobbs et al. range from about −108 to +108 and are significantly correlated with their characteristic ages. Using model magnetic field evolution developed previously based on same data, derive an analytical expression for index which agrees all statistical properties Our is, however, incompatible previous interpretation growth is responsible small values (<3) "baby" ages less than 2 × 103 yr. We find "instantaneous" a...
We test models for the evolution of neutron star (NS) magnetic fields (B). Our model NS spin is taken from an analysis pulsar timing noise presented by Hobbs et al. (2010). first standard a pulsar's magnetosphere in which B does not change with time and dipole radiation assumed to dominate spin-down. find this fails predict both magnitudes signs second derivatives frequencies ($\ddot{\nu}$). then construct phenomenological $B$, contains long term decay (LTD) modulated short oscillations...
We model the evolution of magnetic fields neutron stars as consisting a long term power-law decay modulated by short small amplitude oscillations. Our predictions on timing noise $\ddot\nu$ agree well with observed statistical properties and correlations normal radio pulsars. Fitting to data, we found that their initial parameter implies surface dipole field strength ~ 5E14 G at ~0.4 year old oscillations have between E-8 E-5 period order years. For individual pulsars our can effectively...
We explain some phenomena existing generally in the timing residuals: amplitude and sign of second derivative a pulsar's spin-frequency ($\ddot\nu$), sophisticated residual patterns, which also change with time span data segments. The sample is taken from Hobbs et al.\,(2010), its first have been subtracted solution fitting. classify patterns into different types based on $\ddot\nu$. Then we use magnetic field oscillation model developed our group \citep{zhang12a} to fit successfully kinds...
We consider the influence of magnetic fields on model neutrino-dominated accretion flows (NDAFs) for gamma-ray bursts (GRBs) via assumption that rate disc is totally caused by torque Lorentz force, i.e. braking large-scale and viscosity small-scale fields. calculate structure, composition, luminosity neutrino emission Poynting flux, mass loss driven heating or launched centrifugally fields, based physical condition magnetized NDAFs. It shown favourable to interpret diverse prompt emissions...
Many models of gamma-ray bursts suggest a common central engine: black hole several solar masses accreting matter from disk at an accretion rate 0.01 to 10 M⊙ s−1, the inner region is cooled by neutrino emission and large amounts its binding energy are liberated, which could trigger fireball. We improve neutrino-dominated flows including effects magnetic fields. find that more than half liberated can be extracted directly large-scale fields in disk, it turns out temperature bit lower without...
Abstract The acceleration of LMXB 4U 1820-30 derived from its orbital-period derivative <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mi>P</mml:mi> </mml:mrow> <mml:mo>̇</mml:mo> </mml:mover> <mml:mi mathvariant="normal">b</mml:mi> </mml:msub> </mml:math> was supposed to be the evidence for an Intermediate-mass black hole (IMBH) in Galactic globular cluster (GC) NGC 6624. However, we find that anomalous is...
Abstract We identify the location of RGB bump M4 (NGC 6121) using available photometric data, and measure V RGBB (∼13.57 ± 0.04 mag). According to observed [Fe/H], we compute theoretical isochrones with scaled-solar composition in MESA model alpha-enhanced BaSTI model, respectively. Using a color–magnitude diagram, compare these data obtain magnitude difference δV between predicted magnitude. Based on best fit [Fe/H] = −1.05, [ α /Fe] 0, MLT 2.0, t 13.3 Gyr, is about 0.46 mag. 2.2 ∼ 2.4,...
It is commonly accepted that a neutron star produced, when massive exhausts its nuclear fuel and ends life in core-collapse supernova explosion. This scenario confirmed by the detection of pulsars, which are believed to be rapidly spinning stars, central regions many remnants. Neutron stars their associated remnants should therefore have same ages. As expected, age Crab Pulsar, first connected with remnant (the Nebula), can inferred from current spin period derivative indeed has about...
The observed correlations, between the characteristic ages and dipole surface magnetic field strengths of all pulsars, can be well explained by decay with core temperatures $~2\times10^{8}$ K, $\sim2\times10^{7}$ $\sim10^{5}$ for magnetars, normal radio millisecond respectively; assuming that their are about two orders magnitude larger than true ages, required may reduced a factor 10. follows power-law is dominated solenoidal component ambipolar diffusion mode. In this model, NSs assumed to...
We study the pulsar timing properties and data analysis methods of glitch recoveries. In some cases one first fits times arrival (TOAs) to obtain "time-averaged" frequency ν its derivative , then models them. However, our simulations show that obtained in this way are systematically biased unless time intervals between nearby points TOAs smaller than about 104 s, which is much shorter typical observation intervals. Alternatively, parameters can be by fitting phases directly with relatively...
Abstract The observed long‐term spin‐down evolution of isolated radio pulsars cannot be explained by the standard magnetic dipole radiation with a constant braking torque. However, how and why torque varies remains still controversial, an outstanding problem in our understanding neutron stars. We have constructed phenomenological model surface fields which contains decay modulated short‐term oscillations; pulsar's spin is thus modified its field evolution. predictions this agree precisely...
We model the evolution of spin frequency's second derivative v̈ and braking index n radio pulsars with simulations within phenomenological their surface magnetic field evolution, which contains a long-term power-law decay modulated by short-term oscillations. For pulsar PSR B0329+54, three oscillation components can reproduce its variation. show that "averaged" is different from instantaneous n, magnitude decreases abruptly as time span increases, due to "averaging" effect. The simulated...
Abstract The form of timing residuals due to errors in pulsar spin period P and its derivative <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mi>P</mml:mi> <mml:mo>˙</mml:mo> </mml:mover> </mml:math> , positions, as well proper motions, has been presented for decades the literature. However, residual patterns acceleration have not reported previously, while a Galaxy or globular cluster (GC) will be unavoidably accelerated. coupling...
Abstract We investigate pulsar timing residuals due to the coupling effect of transverse acceleration and Römer delay. The is relatively small usually negligible. Only for pulsars in globular clusters, it possibly important. maximum residual amplitude, which from near surface core cluster, about tens nanoseconds, may hardly be identified most clusters currently. However, an intermediate-mass black hole center a cluster can apparently increase magnitudes. Particularly innermost region, their...
The observed long-term spin-down evolution of isolated radio pulsars cannot be explained by the standard magnetic dipole radiation with a constant braking torque. However, how and why torque varies still remains controversial, which is major issue in understanding neutron stars. Many have been significant changes their rates modulated quasi-periodic oscillations. Applying phenomenological model pulsar timing noise we developed recently to precise data stars, here show that evolutions...
ABSTRACT Millisecond pulsars can serve as effective probes to investigate the presence of intermediate-mass black holes (IMBHs) within Galactic globular clusters (GCs). Based on standard structure models for GCs, we conduct simulations analyse distributions pulsar accelerations central region NGC 6517. By comparing measured obtained from their period derivatives $\dot{P}$ simulated distribution profiles, demonstrate that a excess dark mass is required account accelerations. Our analysis,...
The electric conductivity is studied by the Boltzmann transport equation in highly anisotropic Fermi-liquid model. I point out that minimum conductivity, usually called Ioffe-Regel-Mott limit, immobile direction greatly reduced ratio of hopping matrices because Bloch reflection direction. By comparing with experimental data high-temperature superconductors, find magnitude c-direction resistivity may be partly understood, though its temperature dependence not.