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基于DBBC+Mark 5B记录系统的脉冲星观测
Thesis Advisor汪敏
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天文技术与方法
Keyword脉冲星 基带转换器 Dbbc与mark 5b 相干消色散
Abstract本为主要以云南天文台40米射电望远镜和基带记录终端的脉冲星观测为例,介绍了脉冲星观测系统、相干消色散算法、脉冲计时原理与具体数据处理的结果分析。脉冲星是一种高速自转的天体,自转周期从约1.6ms到几秒。由于其射电辐射具有高度的方向性,且一般自转轴与辐射轴不重合,所以脉冲星信号是以周期脉冲形式到达观测者的。脉冲星在射电波段的辐射符合幂率谱,且平均流量很小,目前所发现的脉冲星在1.4GHz的平均流量约为0.1mJy到1Jy。云南天文台40米天线现配备有S/X双波段制冷接收机,DBBC+Mark 5B的VLBI记录系统。DBBC为中国科学院上海天文台VLBI实验室研制,共有16个通道(上下边带各8个),单通道带宽从0.5MHz以2倍因子一直到32MHz,本振最小可调量为10-6MHz。相比传统的模拟基带转换器,实验证明它有更好的稳定性与带通性能。我们采用此套系统对PSR J0332+5434和PSR J0835-4510进行了观测。观测选用S波段右旋圆极化信号,起始频率为2206.99MHz,总带宽为8MHz。对数据进行相干消色散和平均后,得到这两颗脉冲星的平均脉冲轮廓和PSR J0332+5434的单脉冲图像。并由平均轮廓的展宽随时间的变化关系,对脉冲星的视周期作了一定修正,得到信噪比更高的平均轮廓。并由最近16次的观测求得TOA,用TEMPO2进行处理后得到残差结果图,这说明了我们数据的可用性与准确性,同时证明昆明40米射电望远镜系统开展脉冲星观测是可行的。
Other AbstractThe observations on radio pulsars had been a more and more important part of the whole radio astronomy, and pulsar timing is one of the most significant study of the observations. Things about the observation system, coherent dedispersion, pulsar timing, and data analysis will be introduced in this thesis with the examples of 40-meter antenna and baseband sampling and recording system in Yunnan Observatory. Pulsar is a kind of star with high spin rate that make the rotation periods from 1.6ms to a few seconds. The radio radiation of a pulsar is a pair of narrow beams, however the orientation of the axis and the radiation are always not is a line, which would produce the pulsive signals that we observed. The radiation spectra of the pulsars are according to a pow-law distribution, and the indexes are minus. In general, the mean flux of a pulsar is small, and a specific example is that the mean flux of known pulsars at 1.4GHz is about from 0.1mJy to 1Jy. 40-m antenna in Yunnan Observatory has a dual(S/X band) receiver and a VLBI recording system with DBBC(Digital Base Band Converter) and Mark 5B. DBBC is designed and made by the VLBI-laboratory of Shanghai Observatory, China Academy of Science. It has 16 channels (8 USBs and 8 LSBs), and the bandwidth can be modulated from 0.5MHz to 32MHz with twice factor, the minimum value of the modulation is 10-6MHz. And DBBC showed better stability and bandpass in experimental observations compared to ABBC(Analogue Base Band Converter). We have observed two pulsars, PSR J0332+5434 and PSR J0835-4510, at 2206.99MHz with a bandwidth of 8MHz. After the dedispersion and folding processes, the mean pulse pro¯les of the both were obtained. When the period-improvement with the broadening pattern of the mean pulse profile had been done, the better profiles yielded. Also, we plotted the residuals of the recent 16 observations with TEMPO2 package, and the result was reasonable enough to prove the data from 40-m telescope that was available, which indicated it's proper to launch the pulsar observations here in future.
Subject Area天文学
Document Type学位论文
Recommended Citation
GB/T 7714
李志玄. 基于DBBC+Mark 5B记录系统的脉冲星观测[D]. 北京. 中国科学院研究生院(云南天文台),2010.
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