Effect of Earth''s solid tides on pulsar observations     

Jian-xiang Rong  Nai-yuan Xiao  Ming Zhao 《Chinese Astronomy and Astrophysics》1996,20(4):3-506

It is shown that the effect of the solid tide in the Earth's crust is not negligible in the observed period changes ΔP/P and period rate changes of pulsars.  相似文献   

用软件PSRCHIVE分析脉冲星数据   总被引：1，自引：0，他引：1  

Willem van Straten  Paul Demorest  Stefan Osiowskit 《云南天文台台刊》2012,(3):237-256

PSRCHIVE是一款开源的、面向对象的科学数据分析软件,是一套应用于脉冲星天文学研究的应用包。它通过一系列通用算法实现数据校准与积分、统计分析与模拟以及可视化处理过程,并在脉冲星测时、偏振测量、射频干扰、脉冲变化研究等方面得到了很好的应用。主要概述该软件包含的各种功能,特别是核心应用的各种界面。  相似文献   

基于小波变换的脉冲星弱信号的去噪方法研究   总被引：1，自引：0，他引：1  

汪丽  柯熙政  倪广仁 《天文研究与技术》2008,5(1):49-54

利用小波变换去除噪声的基本原理和方法及消色散方法对毫秒脉冲星极弱信号进行了提取,并对噪声进行了最佳阈值选取实验研究,实现了脉冲星弱信号消色散积累后的检测和抑噪.并研究了软硬阈值估计子等不同阈值消噪技术,进而对PSR 0437-4715信号采用不同方法去噪后的结果进行了分析比较,认为在最大分解层数J=5时对脉冲星信号处理有普适意义.研究结果认为基于小波变换的消噪方法是一种提高信噪比、展示噪声和突变信号的优越方法.  相似文献   

Detecting temporal trends and environmentally-driven changes in the spatial distribution of bottom fishes and crabs on the eastern Bering Sea shelf     

《Deep Sea Research Part II: Topical Studies in Oceanography》2013

This study uses a 30-year time series of standardized bottom trawl survey data (1982–2011) from the eastern Bering Sea shelf to model patterns of summer spatial distribution for various bottom fishes and crabs in response to changes in the areal extent of the cold pool, time lag between surveys, and fluctuations in population abundance. This investigation is the first to include data for the 2006–2010 cold period and to use between-year comparisons of local and shelf-wide spatial indices to test specific responses to three different isothermal boundaries within the cold pool. Distributional shifts in population varied considerably among species and directional vectors for some species were greater in magnitude to the east or west than to the north or south; however, in general, eastern Bering Sea shelf populations shifted southward in response to the increasing cold pool size, and after accounting for differences in temperature and population abundance, there was still a temporal northward shift in populations over the last three decades despite the recent cooling trend. Model results for local and shelf-wide indices showed that survey time lag and cold pool extent had a greater effect on spatial distribution than population abundance, suggesting that density-independent mechanisms play a major role in shaping distribution patterns on the eastern Bering Sea shelf. The area enclosed by the 1 °C isotherm most commonly affects both local and shelf-wide spatial indices suggesting that 1 °C is a more important boundary for describing temperature preferences of eastern Bering Sea bottom fishes and crabs than is the 2 °C isotherm used for designating the physical boundary for the cold pool.  相似文献   

Stereoscopic observations of gamma rays at the Whipple observatory     

F. Krennrich  C.W. Akerlof  J.H. Buckley  J. Bussóns-Gordo  D.A. Carter-Lewis  M.F. Cawley  M.A. Catanese  V. Connaughton  D.J. Fegan  J.P. Finley  J.A. Gaidos  K.H. Harris  A.M. Hillas  R.C. Lamb  M.J. Lang  G. Mohanty  J. Quinn  A.J. Rodgers  H.J. Rose  A.C. Rovero  M.S. Schubnell  G.H. Sembroski  T.C. Weekes  C. Wilson 《Astroparticle Physics》1998,8(4):213-221

Observations of photons at E ≥ 550 GeV from the Crab Nebula are presented and used to assess the potential of multi-telescope systems for γ-ray astronomy.

The Whipple observatory 10 m and 8 m imaging atmospheric erenkov telescopes have been used to provide a stereoscopic view of air showers to make a more complete measurement of air shower parameters. Here we present a measurement of the spread in the arrival direction of primary γ-rays originating from a point source. The data show that the shower arrival direction can be reconstructed with an accuracy of σ = 0.°14.  相似文献   

X射线脉冲星导航可用目标源研究     

赵成仕  陈鼎  蔡宏兵  南仁东 《天文学进展》2011,29(3):334-342

脉冲星具有自转非常稳定的特性,在空间自主导航中有重要的应用前景.选择和研究一组适合于脉冲星导航使用的候选目标源非常重要,决定脉冲星导航精度的主要因素有:导航目标源X射线流量强度、目标源的位置精度和旋转参数精度.对可用于导航的一些X射线源进行了讨论研究,并对最适合做导航研究的转动能驱动的X射线脉冲星进行统计分析.  相似文献   

Variable Quasi Periodic Oscillations during an outburst of the transient X-ray pulsar XTE J1858 + 034     

U. Mukherjee  S. Bapna  H. Raichur  B. Paul  S. N. A. Jaaffrey 《Journal of Astrophysics and Astronomy》2006,27(1):25-35

We have investigated the Quasi Periodic Oscillation (QPO) properties of the transient accreting X-ray pulsar XTE J1858 + 034 during the second outburst of this source in April–May 2004. We have used observations made with the Proportional Counter Array (PCA) of the Rossi X-ray Timing Explorer (RXTE) during May 14–18, 2004, in the declining phase of the outburst. We detected the presence of low frequency QPOs in the frequency range of 140–185 mHz in all the RXTE-PCA observations. We report evolution of the QPO parameters with the time, X-ray flux, and X-ray photon energy. Though a correlation between the QPO centroid frequency and the instantaneous X-ray flux is not very clear from the data, we point out that the QPO frequency and the one day averaged X-ray flux decreased with time during these observations. We have obtained a clear energy dependence of the RMS variation in the QPOs, increasing from about 3% at 3 keV to 6% at 25 keV. The X-ray pulse profile is a single peaked sinusoidal, with pulse fraction increasing from 20% at 3 keV to 45% at 30keV. We found that, similar to the previous outburst, the energy spectrum is well fitted with a model consisting of a cut-off power law along with an iron emission line.  相似文献   

Gamma-Ray Emission from Pulsar Outer Magnetospheres     

Kouichi Hirotani 《Astrophysics and Space Science》2005,297(1-4):81-91

We investigate a stationary pair production cascade in the outer magnetosphere of an isolated, spinning neutron star. The charge depletion due to global flows of charged particles, causes a large electric field along the magnetic field lines. Migratory electrons and/or positrons are accelerated by this field to radiate gamma-rays via curvature and inverse-Compton processes. Some of such gamma-rays collide with the X-rays to materialize as pairs in the gap. The replenished charges partially screen the electric field, which is self-consistently solved together with the energy distribution of particles and gamma-rays at each point along the field lines. By solving the set of Maxwell and Boltzmann equations, we demonstrate that an external injection of charged particles at nearly Goldreich-Julian rate does not quench the gap but shifts its position and that the particle energy distribution cannot be described by a power-law. The injected particles are accelerated in the gap and escape from it with large Lorentz factors. We show that such escaping particles migrating outside of the gap contribute significantly to the gamma-ray luminosity for young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV observed for the Vela pulsar can be explained by this component. We also discuss that the luminosity of the gamma-rays emitted by the escaping particles is naturally proportional to the square root of the spin-down luminosity.  相似文献   

The origin of peculiar jet-torus structure in the Crab nebula     

S. S. Komissarov  Y. E. Lyubarsky 《Monthly notices of the Royal Astronomical Society》2003,344(4):L93-L96

  相似文献   

An Analysis of Average Pulsar Profiles and A Study of the ρ-P relation of Pulsars     

Hua-Xiang Wang  Xin-Ji WuDepartment of Astronomy  Peking University  Beijing  Urumqi Astronomical Station  National Astronomical Observation  Urumqi CAS-PKU Joint Beijing Astrophysics Center  Beijing 《中国天文和天体物理学报》2003,3(5)

Using the method of Gaussian Fit Separation of Average Profile (GF-SAP), we re-examine the average profiles of nine pulsars at several frequencies, ranging from 408-1642 MHz. This method enables us to obtain the number of components for each pulsar, and the parameters for each component, the width, position and amplitude. The ρ-P relation for the inner cone and outer cone are studied separately, and the results are, respectively, ρ = p-0.51±0.05 and ρ= p-0.42±0.06 The results can be interpreted as a confirmation of the double-cone structure of pulsar emission beams. The altitudes of emission region, and the radius-to-frequency-map (RFM) are also examined; for the outer cone, we obtained γ(v) ∝v-0.19±0.09.  相似文献