检索结果-南通市图书馆

Bifurcation timescales in power spectra of black hole binaries and ultraluminous X-ray sources

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 177-182页

作者： wang taishan1 & li tipei1,2.1 department of physics & center for astrophysics,{2.,Beijing 100084,china 2.Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,Beijing 100049,china department of physics & {2. for astrophysics Tsinghua University Beijing China Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China

For black hole binaries(BHBs) and active galactic nuclei(AGNs),bifurcation timescales(BTs) Δtb exist,below which time-domain power is significantly higher than the corresponding Fourier ***-periodic oscillations(QPOs) are removed from the Fourier spectra of BHBs.A relationship between BT,black hole mass and bolometric luminosity is *** anti-correlation between BT and luminosity of Cyg X-1 is *** removing the QPOs,BTs are also obtained for two ultraluminous X-ray sources(ULXs),M82.X-1 and NGC5408 *** results support that they harbor intermediate mass black holes(IMBHs).

关键词： black hole binary ultraluminous X-ray source power spectral density data analysis

New evidence for lack of CMB power on large scales

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： liU Hao1 & li {2.,2.3 1 Key Laboratory of Particle astrophysics, Institute of High Energy physics, Chinese Academy of Sciences, Beijing 100049, china 2.department of physics & center for astrophysics, tsinghua university, Beijing 100084, china 3 department of Engineering physics & center for astrophysics, tsinghua university, Beijing 100084, china Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China department of physics & {2. for astrophysics Tsinghua University Beijing China department of Engineering physics & {2. for astrophysics Tsinghua University Beijing China

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

Inconsistency between WMAP data and released map

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2010年第10期55卷 907-909页

作者： liU Hao1 & li {2.,2.3 1 Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,Beijing 100049,china 2.department of physics & center for astrophysics,tsinghua university,Beijing 100084,china 3 department of Engineering physics & center for astrophysics,tsinghua university,Beijing 100084,china Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China department of physics & {2. for astrophysics Tsinghua University Beijing China department of Engineering physics & {2. for astrophysics Tsinghua University Beijing China

A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (CMB) temperature maps published by the WMAP team is revealed,indicating that there must exist a serious problem in the map making routine of the WMAP *** inconsistency is easy to be confirmed without the use of WMAP map-making *** view of the importance of this issue for cosmology study,we invite readers to check it by themselves.

关键词：威尔金森微波各向异性探测器 WMAP 地图制作宇宙微波背景有序数据制作软件 TOD CMB

The correlation timescale of the X-ray flux during the outbursts of soft X-ray transients

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 161-167页

作者： WU YuXiang1,2.YU WenFei1 & li tipei{2. Shanghai Astronomical Observatory,Shanghai 100012.china 2.department of Engineering physics & center for astrophysics,tsinghua university,Beijing 100084,china Shanghai Astronomical Observatory Shanghai China department of Engineering physics & {2. for astrophysics Tsinghua University Beijing China

Recent studies of black hole and neutron star low mass X-ray binaries(LMXBs) show a positive correlation between the X-ray flux at which the low/hard(LH)-to-high/soft(HS) state transition occurs and the peak flux of the following HS *** analyzing the data from the All Sky Monitor(ASM) onboard the Rossi X-ray Timing Explorer(RXTE),we show that the HS state flux after the source reaches its HS flux peak still correlates with the transition flux during soft X-ray transient(SXT) *** studying large outbursts or flares of GX 339-4,Aql X-1 and 4U 1705-44,we have found that the correlation holds up to 2.0,40,and 50 d after the LH-to-HS state transition,*** time scales correspond to the viscous time scale in a standard accretion disk around a stellar mass black hole or a neutron star at a radius of-104-5 Rg,indicating that the mass accretion rates in the accretion flow either correlate over a large range of radii at a given time or correlate over a long period of time at a given *** the accretion geometry is a two-flow geometry composed of a sub-Keplerian inflow or outflow and a disk flow in the LH state,the disk flow with a radius up to-105 Rg would have contributed to the nearly instantaneous non-thermal radiation directly or indirectly,and therefore affects the time when the state transition occurs.

关键词： accretion disks black hole physics star:individual(Aquila X-1 GX 339-4 4U 1705-44)

Timing in the Time Domain: Cygnus X-1

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and astrophysics 2001年第4期1卷 313-332页

作者： Ti-Pei li (department of {2. and center for astrophysics, tsinghua university, Beijing 100084 High Energy astrophysics Lab., Institute of High Energy {2., Chinese Academy of Sciences, Beijing 100039)E-mail:litp@*** department of physics and {2. for astrophysics Tsinghua University Beijing 100084 High Energy Astrophysics Lab. Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039

Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.

关键词： methods: data analysis - stars: individual (Cygnus X-1) - X-rays: stars

The relativistic consistent angular-momentum projected shell model study of the N=Z nucleus ^(52.Fe

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2009年第10期52卷 1471-1476页

作者： li YanSong1,2.& LONG GuiLu1,2.1 {2. of physics,tsinghua university,Beijing 100084,china 2.center of Nuclear Theory,National Laboratory of Heavy Ion Accelerator of Lanzhou,Lanzhou 730000,china department of physics Tsinghua University Beijing China center of Nuclear Theory National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou China

The relativistic consistent angular-momentum projected shell model(ReCAPS) is used in the study of the structure and electromagnetic transitions of the low-lying states in the N=Z nucleus *** model calculations show a reasonably good agreement with the *** backbending at 12. is reproduced and the energy level structure suggests that neutron-proton interactions play important roles.

关键词： ReCAPS relativistic mean field angular-momentum projection method 52.e neutron-proton interaction

Hard X-ray lags of Cygnus X-1 on short timescales

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 150-152页

作者： JIN Jing1,LU Yu2.3,QU JinLu2.& li tipei1,{2. department of Engineering physics & center for astrophysics,tsinghua university,Beijing 100084,china 2.Key Laboratory of Particle astrophysics,Institute of High Energy physics,Chinese Academy of Sciences,Beijing 100049,china 3 Graduate university of Chinese Academy of Sciences,Beijing 100049,china department of Engineering physics & {2. for astrophysics Tsinghua University Beijing China Key Laboratory of Particle astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing China Graduate university of Chinese Academy of Sciences Beijing China

Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small *** a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin *** new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes *** calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.

关键词： spectral lags Cygnus X-1 data analysis

Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： li Zhihui1,2. ZHANG Hanxin1 & FU Song2.⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development {2.,Mianyang 62.000,china 2.department of Engineering Mechanics,tsinghua university,Beijing 100084,china National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang China department of Engineering Mechanics Tsinghua University Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

Discovery of a high confidence soft lag from an X-ray flare of Markarian 42.

在线全文

学校读者我要写书评

暂无评论

Science china(physics,Mechanics & Astronomy) 2010年第S1期53卷 224-227页

作者： ZHANG YouHong1,HOU ZhengTian2.SHAO li3 & ZHANG Peng1 1 department of {2. and tsinghua center for astrophysics(THCA),tsinghua university,Beijing 100084,china 2.Group of Mathematics and {2.,Shangqiu Medical College,Shangqiu 476100,china 3 Max-Planck-Institut für extraterrestrische Physik,Postfach 1312.Garching 85741,Germany department of physics and {2. center for astrophysics (THCA) Tsinghua University Beijing China Group of Mathematics and physics Shangqiu Medical College Shangqiu China Max-Planck-Institut für extraterrestrische Physik Garching Germany

We present the X-ray variability properties of the X-ray and TeV bright blazar Mrk 42. with a-60 ks long XMM-Newton observation performed on November 9-10,*** source experienced a pronounced flare,of which the inter-band time lags were determined with a very high confidence *** soft(0.6-0.8 keV) X-ray variations lagged the hard(4-10 keV) ones by 1.09+0.11-0.12.ks,and the soft lag increases with increasing difference in the photon *** energy-dependent soft lags can be well fitted with the difference of the energy-dependent cooling timescales of the relativistic electron distribution responsible for the observed X-ray emission,which constrains the magnetic field strength and Doppler factor of the emitting region to be Bδ 1/3-1.78 Gauss.

关键词： BL Lacertae objects:individual:Mrk-42. galaxies:active radiation mechanisms:non-thermal X-rays:galaxies