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A discovery of two slow pulsars with FAST:“Ronin”from the globular cluster M15

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Science China(physics,Mechanics & Astronomy) 2024年第6期67卷 166-180页

作者： Dengke Zhou Pei Wang Di Li Jianhua Fang Chenchen Miao Paulo CCFreire Lei Zhang Dandan Zhang Huaxi Chen Yi Feng Yifan Xiao Jintao Xie Xu Zhang Chenwu Jin Han Wang Yinan Ke Xuerong Guo Rushuang Zhao Chenhui Niu Weiwei Zhu Mengyao Xue Yabiao Wang Jiafu Wu Zhenye Gan Zhongyi Sun Chengjie Wang Jie Zhang Junshuo Zhang Jinhuang Cao Wanjin Lu Research Center for Astronomical Computing Zhejiang LaboratoryHangzhou 311121China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal UniversityBeijing 102206China University of Chinese Academy of Sciences Beijing 100049China New Cornerstone Science Laboratory Shenzhen 518054China Max Planck Institut f¨ur Radioastronomie Bonn 53121Germany Centre for Astrophysics and Supercomputing Swinburne University of TechnologyHawthorn 3122Australia School of Mathematical Sciences School of Physics and Electronic SciencesGuizhou Normal UniversityGuiyang 550001China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guiyang 550001China School of Physics and Electronic Engineering Qilu Normal UniversityJinan 250200China School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China College of Physical Science and Technology Central China Normal UniversityWuhan 430079China Tencent Youtu Lab Shanghai 201103China

Globular clusters harbor numerous millisecond pulsars,but long-period pulsars(P 100 ms)are rarely *** this study,we employed a fast folding algorithm to analyze observational data from multiple globular clusters obtained by the Five-hundredmeter Aperture Spherical radio Telescope(FAST),aiming to detect the existence of long-period *** estimated the impact of the median filtering algorithm in eliminating red noise on the minimum detectable flux density(S_(min))of ***,we successfully discovered two isolated long-period pulsars in M15 with periods approximately equal to 1.928451 and3.960716 s,*** the P-˙P diagram,both pulsars are positioned below the spin-up line,suggesting a possible history of partial recycling in X-ray binary systems disrupted by dynamical encounters later *** to timing results,these two pulsars exhibit remarkably strong magnetic *** the magnetic fields were weakened during the accretion process,then a short duration of accretion might explain the strong magnetic fields of these pulsars.

关键词： pulsar globular cluster FAST

Accretion tori around rotating neutron stars II: Oscillations and precessions

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arXiv 2024年

作者： Matuszková, Monika Török, Gabriel Klimovičová, Kateřina Horák, Jiří Straub, Odele Šrámková, Eva Lančová, Debora Urbanec, Martin Urbancová, Gabriela Karas, Vladimír Research Centre for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-746 01 Czech Republic Astronomical Institute of the Czech Academy of Sciences Boční II 1401 PragueCZ-14100 Czech Republic ORIGINS Excellence Cluster Boltzmannstr. 2 Garching85748 Germany Max Planck Institute for Extraterrestrial Physics Gießenbachstraße 1 Garching85748 Germany

The four characteristic oscillation frequencies of accretion flows are, in addition to the Keplerian orbital frequency, often discussed in the context of the time variability of the black hole and neutron star (NS) low-mass X-ray binaries (LMXBs). These are namely the frequencies of the axisymmetric radial and vertical epicyclic oscillations, and the frequencies of non-axisymmetric oscillations corresponding to the periastron (radial) and Lense-Thirring (vertical) precessions. In this context, we investigate the effect of the quadrupole moment of a slowly rotating NS and provide complete formulae for calculating these oscillation and precession frequencies, as well as their convenient approximations. Simple formulae corresponding to the geodesic limit of a slender torus (and test particle motion) and the limit of a marginally overflowing torus (torus exhibiting a critical cusp) are presented, and furthermore, more general approximate formulae are included to allow calculations for arbitrarily thick tori. We provide the Wolfram Mathematica code used for our calculations together with C++ and PYTHON codes for calculations of the frequencies. Our formulae can be used for various calculations describing the astrophysical signatures of the NSs' superdense matter equation of state. For instance, we demonstrate that, even for a given fixed number of free parameters, a model accounting for fluid flow precession better matches the frequencies of twin-peak quasiperiodic oscillations observed in NS LMXBs than a model using geodesic precession. © 2024, CC BY.

关键词： Geodesy

Habitable zones around almost extremely spinning black holes (black sun revisited)

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arXiv 2020年

作者： Bakala, Pavel Dočekal, Jan Turoňová, Zuzana Research Centre for Computational Physics and Data Processing Faculty of Philosophy and Science Bezrucovonam. 13 OpavaCZ-746 01 Czech Republic M. R. Stefánik Observatory and Planetarium Sládkovicova 41 Hlohovec920 01 Slovakia INAF - Osservatorio Astronomico di Roma Via Frascati 33 Monteporzio Catone Roma00078 Italy

We analyzed the thermodynamics of hypothetical exoplanets at very low Keplerian circular orbits in close vicinity of rapidly spinning supermassive black holes. Such black hole exoplanets are heated by strongly blueshifted and focused flux of the incoming cosmic microwave background (CMB) and cooled by the cold part of the local sky containing the black hole shadow. This gives rise to a temperature difference, which can drive processes far from thermodynamic equilibrium in a hypothetical life form inhabiting black hole exoplanets, similar to the case of a planet heated by the radiation of the parent star and cooled by the night sky. We found that for a narrow range of radii of very low Keplerian circular orbits and for very high spin of a supermassive black hole, the temperature regime of the black hole exoplanets corresponds to the habitable zone around standard stars. The thermodynamics of black hole exoplanets therefore, in principle, does not exclude the existence of life based on known biology. The peak of the multiblackbody spectral profile of the CMB heating the exoplanet is located in the ultraviolet band, but a significant fraction of the flux comes also in the visible and infrared bands. The minimum mass of a black hole ensuring the resistance to tidal disruption of an Earth-like exoplanet orbiting in the habitable zone is estimated to 1.63 108mo. Copyright © 2020, The Authors. All rights reserved.

关键词： Extrasolar planets

Accretion disc backflow in resistive MHD simulations

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arXiv 2022年

作者： Mishra, Ruchi Čemeljić, M. Kluźniak, W. Nicolaus Copernicus Astronomical Center The Polish Academy of Sciences Bartycka 18 Warsaw00-716 Poland Academia Sinica Institute of Astronomy and Astrophysics P.O. Box 23-141 Taipei106 Taiwan Research Centre for Computational Physics and Data Processing Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic

We investigate accretion onto a central star, with the size, rotation rate, and magnetic dipole of a young stellar object, to study the flow pattern (velocity and density) of the fluid within and outside of the disc. We perform resistive MHD simulations of thin α-discs, varying the parameters such as the stellar rotation rate and magnetic field, and (anomalous) coefficients of viscosity and resistivity in the disc. To provide a benchmark for the results and to compare with known analytic results, we also perform purely hydrodynamic simulations (HD) for the same problem. Although obtained for a different situation with differing inner boundary condition, the disc structure in the HD simulations closely follows the analytic solution of Kluźniak & Kita (2000)—in particular a region of "midplane" backflow exists in the right range of radii, depending on the viscosity parameter. In the MHD solutions, whenever the magnetic Prandtl number does not exceed a certain critical value, the midplane backflow exists throughout the accretion disc, extending all the way down to the inner transition zone where the disc transitions to a magnetic funnel flow. For values of the magnetic Prandtl number close to the critical value the backflow and the inner disc undergo a quasiperiodic radial oscillation, otherwise the backflow is steady, as is the disc solution. From our results, supplemented by our reading of the literature, we conclude that midplane backflow is a real feature of at least some accretion discs, whether HD α-discs or MHD discs, including ones driven by MRI turbulence. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Particle motion around luminous neutron stars: effects of deviation from Schwarzschild spacetime

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arXiv 2024年

作者： Vieira, Ronaldo S.S. Wielgus, Maciek Centro de Ciências Naturais e Humanas Universidade Federal do ABC SP Santo André09210-580 Brazil Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Research Centre for Computational Physics and Data Processing Institute of Physics Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic

We study trajectories of test particles around a luminous, static, spherically symmetric neutron star, under the combined influence of gravity and radiation. In general relativity, for Schwarzschild spacetime, an equilibrium sphere (the Eddington Capture Sphere) is formed for near-Eddington luminosities. We generalize these results to a broad class of static, spherical spacetimes. We also study the dynamics of particles in a strong radiation field in spherical spacetimes. The results are illustrated for two cases, Reissner-Nordström spacetime of a charged spherical object in general relativity and Kehagias-Sfetsos spacetime, arising from the Hořava–Lifshitz gravity theory. Our findings apply to neutron stars under gravitational field equations different from the vacuum Einstein field equations of general relativity, such as in modified theories of gravity, the only requirement being that test particles follow geodesics in the absence of the radiation field. The effects that we describe are, in principle, measurable through observations of X-ray bursts of neutron stars. Hence, detailed future studies could use such observations to test gravity theories in the strong-field regime, provided that the impact of the spacetime geometry can be disentangled from the astrophysical uncertainties. Copyright © 2024, The Authors. All rights reserved.

关键词： Spheres

Three-dimensional general relativistic Poynting-Robertson effect. III. Static and non-spherical quadrupolar massive source

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arXiv 2020年

作者： de Falco, Vittorio Bakala, Pavel Falanga, Maurizio M. R. Štefánik Observatory Planetarium Sládkovičova 41 Hlohovec920 01 Slovakia Research Centre for Computational Physics and Data Processing Faculty of Philosophy & Science Silesian University in Opava Bezručovo nám. 13 OpavaCZ-74601 Czech Republic International Space Science Institute Hallerstrasse 6 Bern3012 Switzerland

We investigate the three-dimensional (3D) motion of a test particle in the gravitational field generated by a non-spherical compact object endowed with a mass quadrupole moment, described by the Erez-Rosen metric, and a radiation field, including the general relativistic Poynting-Robertson (PR) effect, coming from a rigidly rotating spherical emitting source located outside of the compact object. We derive the equations of motion for test particles influenced by such radiation field, recovering the two-dimensional (2D) description, and the weak-field approximation. This dynamical system admits the existence of a critical hypersurface, region where gravitational and radiation forces balance. Selected test particle orbits for different set of input parameters are displayed. The possible configurations on the critical hypersurfaces can be either latitudinal drift towards the equatorial ring or suspended orbits. We discuss about the existence of multiple hypersurface solutions through a simple method to perform the calculations. We graphically prove also that the critical hypersurfaces are stable configurations within the Lyapunov theory. Copyright © 2020, The Authors. All rights reserved.

关键词： Dynamical systems

Optimization of escape kinetics by reflecting and resetting

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arXiv 2023年

作者： Capala, Karol Dybiec, Bartlomiej Personal Health Data Science Group Sano - Centre for Computational Personalised Medicine Czarnowiejska 36 Kraków30-054 Poland Institute of Theoretical Physics Mark Kac Center for Complex Systems Research Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Lojasiewicza 11 Kraków30-348 Poland

Stochastic restarting is a strategy of starting anew. Incorporation of the resetting to the random walks can result in the decrease of the mean first passage time, due to the ability to limit unfavorably meandering, sub-optimal trajectories. In the following manuscript, we examine how stochastic resetting influences escape dynamics from the (−∞, 1) interval in the presence of the single-well power-law |x|κ potentials with κ > 0. Examination of the mean first passage time is complemented by the analysis of the coefficient of variation, which provides a robust and reliable indicator assessing efficiency of stochastic resetting. The restrictive nature of resetting is compared to placing a reflective boundary in the system at hand. In particular, for each potential, the position of the reflecting barrier giving the same mean first passage time as the optimal resetting rate is determined. Finally, in addition to reflecting, we compare effectiveness of other resetting strategies with respect to optimization of the mean first passage time. Copyright © 2023, The Authors. All rights reserved.

关键词： Stochastic systems

Graph-cut based antialiasing for Doppler ultrasound color flow medical imaging

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Graph-cut based antialiasing for Doppler ultrasound color fl...

IEEE Visual Communications and Image processing (VCIP)

作者： Artem M. Yatchenko Andrey S. Krylov Andrey V. Gavrilov Ivan V. Arkhipov Laboratory of Mathematical Methods of Image Processing Faculty of Computational Mathematics and Cybernetics Lomonosov Moscow State University Russia D.V. Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University Russia B.V. Petrovsky National Research Centre of Surgery Moscow Russia

An unwrapping method for Doppler ultrasound color flow medical images has been developed. It is based on a image digitizing procedure to construct the areas graph. The minimization unwrapping procedure of the velocity... 详细信息

关键词： Image color analysis Doppler effect Minimization Ultrasonic imaging Imaging Blood flow Heart

Dynamically producing asymmetric interferometric power under dephasing

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Physical Review A 2022年第4期105卷 042612-042612页

作者： Hong-biao Li Qiang Zheng Qi-jun Zhi Yong Li School of Physical Science and Technology Tiangong University Tianjin 300387 China School of Physics and Electronic Science Guizhou Normal University Guiyang 550001 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal University Guiyang 550001 China Beijing Computational Science Research Center Beijing 100193 China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China

Interferometric power, based on the minimal quantum Fisher information in a black-box interferometer, can be used to measure general quantum correlation in a bipartite system. This paper explores the interferometric power of a two-qubit system in a common bath. It is found that, for an initially separable state, the interferometric power of the system can be produced with the time evolution, even subject to the dephasing environment. Moreover, it is asymmetric with respect to the local evolution implementing on one subsystem or another. Our result would be useful to quantum information processing beyond entanglement, especially in one-sided device-independent task.

关键词： Quantum metrology