检索结果-南通市图书馆

An accreting low magnetic field magnetar for the ultraluminous X-ray source in M82

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2015年第4期15卷 517-524页

作者： hao tong Xinjiang Astronomical Observatory Chinese Academy of Sciences

One ultraluminous X-ray source in M82 has recently been identified as an accreting neutron star （named NuSTAR J095551＋6940.8）. It has a super-Eddington luminosity and is spinning up. An aged magnetar is more likely to be a low magnetic field magnetar. An accreting low magnetic field magnetar may explain both the super- Eddington luminosity and the rotational behavior of this source. Considering the effect of beaming, the spin-up rate is understandable using the traditional form of accretion torque. The transient nature and spectral properties of M82 X-2 are discussed. The theoretical range of periods for accreting magnetars is provided. Three observational appearances of accreting magnetars are summarized.

关键词： accretion -- pulsars: individual (NuSTAR J095551+6940.8) -- stars:magnetars -- stars: neutron

A note on the puzzling spindown behavior of the Galactic center magnetar SGR J1745-2900

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2015年第9期15卷 1467-1474页

作者： hao tong Xinjiang Astronomical Observatory Chinese Academy of Sciences

SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars, a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745-2900. This magnetar is shortly expected to have a maximum spindown rate.

关键词： pulsars: individual (SGR J1745-2900) -- stars: magnetar -- stars: neu-tron -- stars: winds

Understanding the circular polarization of fast radio bursts observed by the Five-hundred-meter Aperture Spherical Radio Telescope

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2022年第10期65卷 155-156页

作者： hao tong School of Physics and Materials Science Guangzhou UniversityGuangzhou 510006China

China's Five-hundred-meter Aperture Spherical Radio Telescope(FAST)is the world's largest single-disk radio *** of its high sensitivity,it can reveal the most intriguing properties of pulsars and fast radio bursts(FRBs).

关键词： bursts telescope observed

同方期刊数据库

On the possible wind nebula of magnetar Swift J1834.9-0846:a magnetism-powered synchrotron nebula

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2016年第9期16卷 91-94页

作者： hao tong Xinjiang Astronomical Observatory Chinese Academy of Sciences

Recently, the magnetar Swift J1834.9-0846 has been reported to have a possible wind nebula. It is shown that both the magnetar and its wind nebula are understandable in the wind braking scenario. The magnetar＇s rotational energy loss rate is not enough to power the particle luminosity. The required particle luminosity should be about 10^36 erg s^- 1 to 10^38 erg s^-1. It is obtained in three different approaches： considering wind braking of Swift J1834.9-0846; the spectral and spatial observations of the wind nebula; and an empirical upper bound on wind nebula X-ray luminosity. The nebula magnetic field is about 10-4 G. The possible wind nebula of Swift J1834.9-0846 should be a magnetar wind nebula. It is powered by the magnetic energy released from the magnetar.

关键词： pulsars individual (Swift J1834.9-0846) -- stars magnetars -- stars neutron -- winds and outflows

Circular Polarization of Fast Radio Bursts in the Curvature Radiation Scenario

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2022年第7期22卷 206-213页

作者： hao tong Hong-Guang Wang School of Physics and Materials Science Guangzhou UniversityGuangzhou 510006China

The curvature radiation is applied to the explanation of the circular polarization of fast radio bursts(FRBs).Significant circular polarization is reported in both apparently non-repeating and repeating *** radiation can produce significant circular polarization at the wing of the radiation *** the curvature radiation scenario,in order to see significant circular polarization in FRBs,(1) more energetic bursts,(2) bursts with electrons having higher Lorentz factor,and(3) a slowly rotating neutron star at the center are *** rotational period of the central neutron star may explain why some FRBs have high circular polarization,while others do *** possible difference in refractive index for the parallel and perpendicular components of electric field,the position angle may change rapidly over the narrow pulse window of the radiation *** position angle swing in FRBs may also be explained by this non-geometric origin,besides that of the rotating vector model.

关键词： stars:magnetars (stars:)pulsars:general polarization

Experimental Research on Effects of Process Parameters on Servo Scanning 3D Micro Electrical Discharge Machining

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第1期25卷 114-121页

作者： tong hao LI Yong HU Manhong State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Servo scanning 3D micro electrical discharge machining (3D SSMEDM) is a novel and effective method in fabricating complex 3D micro structures with high aspect ratio on conducting materials. In 3D SSMEDM process, the axial wear of tool electrode can be compensated automatically by servo-keeping discharge gap, instead of the traditional methods that depend on experiential models or intermittent compensation. However, the effects of process parameters on 3D SSMEDM have not been reported up until now. In this study, the emphasis is laid on the effects of pulse duration, peak current, machining polarity, track style, track overlap, and scanning velocity on the 3D SSMEDM performances of machining efficiency, processing status, and surface accuracy. A series of experiments were carried out by machining a micro-rectangle cavity (900 μm×600 μm) on doped silicon. The experimental results were obtained as follows. Peak current plays a main role in machining efficiency and surface accuracy. Pulse duration affects obviously the stability of discharge state. The material removal rate of cathode processing is about 3/5 of that of anode processing. Compared with direction-parallel path, contour-parallel path is better in counteracting the lateral wear of tool electrode end. Scanning velocity should be selected moderately to avoid electric arc and short. Track overlap should be slightly less than the radius of tool electrode. In addition, a typical 3D micro structure of eye shape was machined based on the optimized process parameters. These results are beneficial to improve machining stability, accuracy, and efficiency in 3D SSMEDM.

关键词： micro electrical discharge machining(micro EDM) servo scanning machining 3D micro-structure process parameter

The timing behavior of magnetar Swift J1822.3—1606: timing noise or a decreasing period derivative?

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2013年第10期13卷 1207-1212页

作者： hao tong Ren-Xin Xu Xinjiang Astronomical Observatory Chinese Academy of Sciences KIAA and School of Physics Peking University

The different timing results of the magnetar Swift J1822.3—1606 are analyzed and understood *** is noted that different timing solutions are caused not only by timing noise,but also because the period derivative is decreasing after the *** the decreasing period derivative and the large timing noise may originate from wind braking associated with the *** timing of Swift J1822.3—1606 will help clarify whether or not its period derivative is decreasing with time.

关键词： pulsars:individual(Swift J1822.3—1606) stars:magnetar stars:neutron

Online Measurements of High-band Grid Impedance Using Variable Frequency Carrier Based PWM Schemes

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2021年第1期7卷 128-139页

作者： Zheyu Miao hao tong Wenxi Yao Zhengyu Lu the College of Electrical Engineering Zhejiang UniversityHangzhou 310027China

Grid-connected power electronic devices, such asvoltage-source inverters (VSIs), are increasingly installed in thegrid for the utilization of renewable energy sources. Under highpenetration, the weak grid contains plentiful harmonics and complexgrid impedance values, which have deep impacts on systemstability as well as its control performance. Online impedancemeasurement is needed for impedance based adaptive controland analysis. This paper proposes a variable carrier frequencyPWM (VCFPWM) based online grid impedance measurementtechnology. This method broadens the available working rangein the high frequency band without increasing the low bandperturbations. Through good analysis and design of the carrierfrequency, the VCFPWM method injects sufficient harmonicenergy at specified high frequency points and guarantees lowTHDs at the same time. The detailed design considerations ofthe carrier frequency are clarified and the characteristics of theVCFPWM based excitations are analyzed in this paper. Finally,the simulation and experimental results based on a three-phasegrid-connected VSI are presented to verify the effectiveness ofthe proposed method.

关键词： Carrier frequency harmonic impedance measurement voltage-source inverters weak grid

Improbability of DUrca Process Constraints EOS

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2007年第6期7卷 809-813页

作者： hao tong Qiu-He Peng Department of Astronomy Nanjing University Nanjing 210093

According to recent observational and theoretical progresses, the DUrca process （direct Urca process） may be excluded from the category of neutron star cooling mechanisms. This result, combined with the latest nuclear symmetry energy experiments, will provide us an independent way of testing the EOS （equation of state） for supernuclear density. For example, soft EOSs, such as FPS, will probably be excluded.

关键词： equation of state -- neutrinos -- stars neutron