脉冲星Geminga MeV 脉冲辐射证据

利用直接解调方法分析COMPTELVPI数据,得到了脉冲星Geminga10-30MeV脉冲辐射存在的证据：全位相及分位相成像均得到了Geminga．分位相成像结果显示,光变曲线的峰值位于pulse1附近,而其它位相区域只能给出上限．由于成像分析不存在选择效应,该成像结果表明,Geminga在MeV能区仍存在脉冲辐射．虽然Geminga的弱MeV辐射使得很难就VP1数据作时间分析,但仍得到了一些周期信号的迹象,并且与成像结果不相矛盾．进一步考察EGRET观测Geminga在30MeV以上的强度比Pulse2／Pulse1,发现在VP1观测的较低能区,Pulse1有渐强于Pulse2的趋势,这和我们在MeV能区的成像及时间分析结果相一致．成像得到的流强表明,Geminga的能谱至少在10MeV以上不应出现偏折．     

一颗与众不同的脉冲星Geminga

最近，一个困扰人们达十几年之久的γ射线源Ｇｅｍｉｎｇａ被证认为Ｘ、γ射线脉冲星，其光学对应体也被确定为一颗光谱偏蓝的２５等星。对Ｇｅｍｉｎｇａ脉冲星的确证说明存在着一类没有射电辐射的脉冲单星。     

脉冲星Geminga MeV脉冲辐射证据

利用直接解调方法分析ＣＯＭＰＴＥＬ ＶＰ１数据,得到了脉冲星Ｇｅｍｉｎｇａ １０－３０ＭｅＶ脉冲辐射存在的证据;全位相及分位相成像均得到了Ｇｅｍｉｎｇａ。分位相成像结果显示,江变曲线的峰值位于ｐｕｌｓｅ１附近,而闰相区域只能给出上限。由于成 像分析不存在的选择效应,该成像结果表明,Ｇｅｍｉｎｇａ在ＭｅＶ能区仍存在脉冲辐射,虽然Ｇｅｍｉｎｇａ的弱ＭｅＶ辐射使得很难就ＶＰ１数据作时间分析,但仍得到了一     

用位相相关方法测量Geminga脉冲星的守时参数

利用γ射线脉冲星Ｇｅｍｉｎｇａ自旋及频率变化的稳定性，采用位相相关的方法分析了ＥＧＲＥＴ对脉冲星Ｇｅｍｉｎｇａ四次观测间隔较长的数据，得到较为准确的守时参数ｆ．位相相关的结果与更长数据段折叠搜索的结果较为接近，表明对于自旋和频率变化都较为稳定的γ射线脉冲星，位相相关分析方法可以作为提高脉冲星参数精度的有效方法．     

用位相相关方法测量Geminga脉冲星的守时参数

利用γ射线脉冲星Ｇｅｍｉｎｇａ自旋及频率变化的稳定性，采用位相相关的方法分析了ＥＧＲＥＴ对脉冲星Ｇｅｍｉｎｇａ四次观测间隔较长的数据，得到较为准确的守时参数ｆ，位相相关的结果与更长数据段折叠搜索的结果较为接近，对于自旋和频率变化都较为稳定的γ射线脉冲星，位相相关分析方法可以作为提高脉冲星参数精度的有效方法。     

Geminga缺射电脉冲的一种可能机制

应用Ｕｓｏｖ和Ｍｅｌｒｏｓｅγ射线脉冲星的修正的极冠区内间隙模型,得出了γ射线脉冲星Ｇｅｍｉｎｇａ为什么没有射电脉冲辐射或射电脉冲辐射很弱的一种可能解释．同时,也可看出,中子星表面的多极场有着重要的作用．     

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。     

Pulsar Observations and Structure of the Local ISM

Results from new observations of pulsars using the Ooty Radio Telescope(ORT) are used for investigating the structure of the Local InterstellarMedium (LISM) and the nature of the plasma turbulence spectrum in theInterstellar Medium (ISM). The observations show anomalous scintillationtowards several nearby pulsars, and these are modelled in terms oflarge-scale spatial inhomogeneities in the distribution of plasma densityfluctuations in the LISM. A 3-component model, where the Solar neighborhoodis surrounded by a shell of enhanced plasma turbulence, is proposed for theLISM. The inferred scattering structure is strikingly similar to the LocalBubble. The nature of the plasma turbulence spectrum is found to be Kolmogorov-like in the spatial scale range 10⁶ m to 10¹¹ m,and there is evidence for excess power at larger spatial scales.     

脉冲星观测中的日月岁差效应

脉冲星周期和周期变率的测量中存在着日月岁差效应.通过对日月岁差效应的分析,发现它已经影响到了某些脉冲星的周期的精密测量.在对1771颗脉冲星测量周期的分析和检测中,有81颗脉冲星的测量周期在它们的测量精度范围内受到日月岁差效应的影响.随着观测精度的提高,在以后的脉冲星周期和周期变率的精密测量中,这些影响应该得到相应的改正.     

The Effect of Lunisolar Precession on Pulsar Observations

In the measurements of pulsars’ periods and their rates of change there exists the effect of lunisolar precession. Via the analysis of this effect, we find that it can affect the accurate measurements of the periods of certain pulsars. An investigation of the periods of 1771 pulsars reveals that the measured periods of 81 pulsars suffer the influence of lunisolar precession in the range of the accuracy of measurements. With the improvement of the precision of measurements of pulsars’ periods and their change rates, this effect should get the corresponding corrections.     

Observations of Giant Pulses of the Crab Pulsar

The Crab Pulsar was observed at 1540 MHz with the 25m radio telescope at Urumqi with a filterbank de-dispersion backend. A total of 2436 giant pulses with pulse energies larger than 4300 Jy μs were detected in two observing sets. All of these giant pulses are located in the main pulse (MP) and inter pulse (IP) windows of the average profile of the Crab Pulsar. The ratio of the numbers of giant pulses detected in the IP and MP windows is about 0.05. Our results show that, at 1540 MHz, the emission in the IP is contributed by giant and normal pulses, while that in the MP is almost dominated by giant pulses. The distribution of energy of the 2436 giant pulses at 1540 MHz can be described by a power-law with index α=3.13±0.09. The intrinsic threshold of giant pulse energy in the MP window is about 1400 Jy μs at 1540 MHz.     

High-Latitude Inner Solar Wind from Pulsar Radio Sounding Observations

Radio sounding experiments probing the inner solar wind by polarized pulses of pulsars PSR B0525+21 (J0528+22) and PSR B531+21 (J0534+22) were carried out in June 2005 and June 2007 on the large phased array of the Lebedev Physical Institute at 111 MHz in the period near the minimum of the solar-activity cycle. The lines of sight toward these pulsars were close to the Sun during the observation sessions. The arrival-time delays for pulses from PSR J0534+22 are used to derive the radial dependence of the mean density of the circumsolar plasma. Comparison with Stanford coronal magnetic-field data, STEREO SECCHI, and SOHO EIT synoptic maps shows that the results are related to the polar coronal holes. The ambient density radial distribution derived from the arrival-time delays for pulses from PSR J0534+22 is stronger than inverse-square law indicating that the acceleration of fast, high-latitude solar-wind outflows, continues to heliocentric distances of (5–10)R _S, where R _S is the solar radius. The mean plasma density near a solar-activity minimum in the investigated range of heliocentric distances is substantially lower than at the solar-activity maximum.