毫秒脉冲量计时方法和实验研究的进展

介绍脉冲星的时间频率特征。阐述了该课题研究的意义,国内外毫秒脉冲星计时理论,方法和技术方面的研究进展,分析了我国开展毫秒脉冲星计划时研究的可行性、目标及任务,并对其中的关键问题给予讨论,最后对该领域的研究发展前景进行展望。     

毫秒脉冲星计时观测进展

在评述国际上毫秒脉冲星长期计时观测成果的基础上，比较了由毫秒脉冲星自转定义的脉冲星时PT与原子时AT的长期稳定度。毫秒脉冲星PSR B1855 09 15yr的长期稳定度优于原子时TAI—USNO，而接近原子时TAI—PTB；其短期稳定度主要受到计时观测误差的限制。毫秒脉冲星PSR J0437-47 1yr以上的稳定度明显优于上述两原子时系统。毫秒脉冲星PSR B193T 21和PSR J1713 07的长期稳定度受到低频噪声影响，但仍能对综合脉冲星时PTens的建立与保持作出贡献。另外，介绍和评述了国际上脉冲星计时阵的现状及发展。随着脉冲星计时阵的实旅，在脉冲星时间标准研究、原子时误差、太阳系历表误差研究和引力波探测方面将会取得重要成果；展望了国际上平方公里望远镜(SKA)在毫秒脉冲星计时观测方面的发展前景。     

毫秒脉冲星定时研究进展

毫秒脉冲星守时的理论和方法研究己取得重要进展,利用现有2颗毫秒脉冲星约10yr的计时观测资料分析得到的 TAI-PT,其长期稳定度为 2×10－14。采用合适的长期稳定度算法,由多颗毫秒脉冲星计时观测可以建立综合脉冲星时间尺度。它可以成为与原子时系统比较的重要手段,并对原子时长期稳定度的改进做出贡献。介绍了该领域研究的基本状况,重点对毫秒脉冲星守时的理论方法,综合脉冲星时间及与原子时的关系等进行了讨论和评述。对由双星系统内毫秒脉冲星的轨道运动定义的双星脉冲星时也做了介绍。     

脉冲星时稳定度及可能应用

给出了毫秒脉冲星长期计时观测最新结果和脉冲星时与原子时频率稳定度的比较。指出脉冲星时频率稳定度的提高受到计时观测误差的限制,讨论了提高毫秒脉冲星计时观测精度的方法。随着脉冲星计时阵的实施,脉冲星时的应用已为期不远。可能的应用包括毫秒脉冲星与原子钟结合守时、建立综合脉冲星时和用脉冲星计时阵检测原子时误差等方面。     

毫秒脉冲星计时观测的研究进展

对毫秒脉冲星时间测量的理论、方法和技术研究的进展进行了阐述。根据近年来取得的观测研究结果,毫秒脉冲星计时测量误差～2×10－7秒,毫秒脉冲星自转周期稳定性足以和现代原子钟相媲美：其相对频率不稳定度达到1×10－14（1年≤γ≤5．2年）,并可望更高。近年来,脉冲星计时观测系统的接收灵敏度获得很大改进,计时观测的数据采集、处理技术、脉冲到达时间分析模型研究等都有长足发展。通过综合脉冲星时间算法得到的脉冲星时间尺度将比现代原子时具有更高的长期稳定度。叙述了脉冲星的物理特性及有关计时观测系统的技术成果,如观测频率和带宽的选择,消色散和接收系统灵敏度等问题。最后对毫秒脉冲星时间测量的误差源进行了讨论,并对脉冲星时间尺度的应用前景做了展望。     

基于实测数据的综合脉冲星时研究

介绍了脉冲星计时在几个重要方面的应用,给出了脉冲星时间尺度的简要定义.基于澳大利亚PARKES天文台的毫秒脉冲星实测计时数据,建立了基于4颗毫秒脉冲星的综合脉冲星时,并将其稳定度σz与原子时进行比较,最后分析了影响综合脉冲星时的几个重要因素及其对脉冲星计时精度的影响与应用.     

毫秒脉冲量计时方法的研究进展和前景

介绍脉冲星的时间频率特征,脉冲星时间研究的意义,毫秒脉冲星计时理论方法和技术方面的研究进展,对其中的关键问题给予讨论．并对其发展前景进行了展望．     

脉冲星时间特征和多星计时观测

在评介脉冲星时研究发展趋势的基础上,讨论了基于毫秒脉冲星自转的脉冲星时间的短期特征和长期稳定度,并对影响其稳定度的因素作了初步分析.50m射电望远镜计时观测的目的之一就是综合脉冲星时研究.对于50m望远镜计时观测的选星和由多星观测进行综合脉冲星时研究中的数据分析问题进行了讨论.     

脉冲星时间尺度及其TOA预报初步分析

在简述国际天文学会(IAU)定义的几种不同时间尺度的基础上,重点讨论脉冲星计时观测中时间坐标相对论转换问题。脉冲星计时观测资料分析应该参考地球时TT,并将TT转换为质心坐标时TCB或质心力学时TDB。基于IAU重新定义的TDB,讨论和比较了时间坐标转换的解析算法和利用太阳系天体历表的数值积分算法。分析了TCB和TDB对脉冲星自转参数测量的影响。最后,以毫秒脉冲星PSR B1855+09的计时模型为例,初步分析了脉冲星脉冲到达时间的预报问题。     

引力波引起的脉冲星计时残差模拟与分析

为了能将引力波引起的脉冲星计时残差从总的脉冲星计时残差中分离出来,我们介绍了3种形式的引力波(单一持续的引力波、单一瞬时的引力波和随机引力波背景)及其对脉冲星计时残差的影响,并利用脉冲星计时处理软件Tempo2进行了模拟,对模拟得到的这三种引力波源引起的脉冲星计时残差进行了分析比较。该工作在脉冲星时间尺度的建立及其应用方面具有参考意义。     

四种综合脉冲星时算法比较

由单颗脉冲星定义的脉冲星时受多种噪声源的影响,其短期和长期稳定度都不够好.为了削弱这些噪声源对单脉冲星时的影响,可以采取合适的算法对多个单脉冲星时进行综合得到综合脉冲星时,从而提高综合脉冲星时的长期稳定度.文中介绍4种综合脉冲星时算法:经典加权算法、小波分析算法、维纳滤波算法和小波域中的维纳滤波算法,将这4种算法分别应用于Arecibo天文台对两颗毫秒脉冲星PSR B1855+09和PSRB1937+21观测得到的计时残差并作出比较.     

Processing and Analysis of X-ray Timing Data for Crab Pulsartwo

The X-ray timing data for the Crab pulsar obtained by the Chinese X-ray pulsar navigation test satellite are processed and analyzed. The method to build the integrated and standard X-ray pulse profiles of the Crab pulsar by using the X-ray pulsar observation data and the satellite orbit data is described. The principle and algorithm for determining the pulsar's pulse time of arrival (toa) in the frequency domain are briefly introduced. The pulsar's pulse time of arrival is calculated by using the timing data of 50 min integration for each set of observational data. By the comparison between the observed Crab pulsar's pulse time of arrival at the solar system barycenter and that predicted with the Crab pulsar ephemeris, it is found that the timing accuracy is about 14 μs after the systematic error is removed by a quadratic polynomial fitting.     

New phase-coherent measurements of pulsar braking indices

Pulsar braking indices offer insight into the physics that underlies pulsar spin-down. Only five braking indices have been measured via phase-coherent timing; all measured values are less than 3, the value expected from magnetic dipole radiation. Here we present new measurements for three of the five pulsar braking indices, obtained with phase-coherent timing for PSRs J1846-0258 (n=2.65±0.01), B1509-58 (n=2.839±0.001) and B0540-69 (n=2.140±0.009). We discuss the implications of these results and possible physical explanations for them.      

毫秒脉冲星在时间计量中的可能应用

在分析射电脉冲星的自转和时间尺度的基本特征及其相互之间的关系的基础上，讨论了毫秒脉冲星在时间工作中的可能应用。基于毫秒脉冲星的到达时间的测量，经过必要的时空转换、改正及参数拟合，可以建立脉冲星时及综合脉冲星时。虽然脉冲星时及综合脉冲星时对原子有所依赖，但它们，特别是综合脉冲星时，可以用来将原子时的准确度从一个时段传递到另一个时段，并可用来分析原子时的长期稳定度。另外，可以利用双星脉冲星的轨道运动的相位来定义一种动力学时间尺度－－双星脉冲星时。     

Application of ‘CLEAN’ in the power spectral analysis of non-uniformly sampled pulsar timing data

Spectral analysis of the residual pulsearrival times of pulsars is a useful tool in understanding the nature of the underlying processes that may be responsible for the timing noise observed from pulsars. Power spectra of pulsar timing residuals may be described by one or a combination of powerlaws. As these spectra are expected to be very steep, it is important to ensure a high dynamic range in the estimation of the spectrum. This is difficult in practice since one is, in general, dealing with timing measurements made at unevenly placed epochs. In this paper, we present a technique based on, ‘CLEAN’ to obtain high dynamic range spectra from unevenly sampled data. We compare the performance of this technique with other techniques including some that were used earlier for estimation of power spectra of pulsar timing residuals.     

Pulsar sensitivity studies of the GLAST large area telescope

In this contribution we present our preliminary investigation on pulsar sensitivity of the Large Area Telescope, the main instrument aboard the GLAST mission. In particular we concentrated our attention to pulsars located at low galactic latitudes. We created a set of simulated pulsars having different fluxes in an array of galactic coordinates separated by a distance greater than the LAT Point Spread Function in order to avoid confusion between adjacent sources. Galactic gamma-ray sky background as used during the second LAT Data Challenge (DC2) is also included. We then run an automatic routine for testing periodicity for all the pulsars considering an opportune timing solution. In this way we can obtain a map of the sensitivity of the periodic searches for different fluxes and for various Galactic latitudes. Some assumptions have been made by simulating the pulsar sources, but this study is a first step toward an estimate for pulsed emission sensitivity of the GLAST LAT. The pulsed flux sensitivity profile we generate could also be input to a population synthesis code of Galactic pulsars in order to obtain more accurate predictions of the number of expected pulsar detections by GLAST. On behalf of the GLAST LAT Collaboration.     

Power spectrum analysis of the timing noise in 18 southern pulsars

Power spectra of the timing noise observed in 18 southern pulsars have been derived using a novel technique, based on the CLEAN algorithm. Most of the spectra are well described by a single- or double-component power-law model. Some of these spectra can be interpreted in the context of one or more of the current timing noise models. The results combined with those obtained from the time-domain analyses of the timing activity in these pulsars are used to assess the viability of the various theoretical models of pulsar timing noise.     

Radiation properties of pulsar magnetospheres: observation,theory, and experiment

In the three decades since their discovery, the accumulated body of observational data from pulsar sources puts constraints on models that seek to explain their periodic radiation. This paper reviews this data, reports on a VLA search for haloes predicted by an early model, and reinvestigates a magnetospheric disk-field-aligned-current transmission line system as the origin of the observed radiation, with external wave excitation by as yet an unexplained source. Three dimensional, fully electromagnetic particle-in-cell simulations of the pulsar surface and magnetosphere are used to explore the waveshape and polarization properties of the observed radiation.     

Slow glitches in the pulsar B1822-09

The pulsar B1822-09 (J1825-0935) experienced a series of five unusual, slow glitches over the 1995–2004 interval. The results of further study of this unusual glitch phenomenon are presented. It is also reported the detection a new glitch of typical signature that occurred in the pulsar period in 2006 January.