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arXiv 1406.5841astro-ph.HE
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150个射电正常谱脉冲宽度的频率依赖性

Frequency dependence of pulse width for 150 radio normal pulsars

J. L. Chen, H. G. Wang

摘要:

本文研究了欧洲脉冲星网中150颗正常星的脉宽频率依赖性,其中10%的多频脉宽符合Thorsett关系W_{10} =Aν^μ+ W_{\rm 10, min}。根据最佳拟合关系,计算了0.4~GHz和4.85~GHz脉冲宽度变化的相对分数η=(W_{4.85} - W_{0.4})/ W_{0.4}。结果发现,81例(54%)患者有$η<-10$(A组),在高频下表现出明显的轮廓变窄,40例(27%)患者有$-$ 10 $\leqη\leq 10$(B组),意味着脉冲宽度的边缘变化,29例(19%)患者有$η>10$(C组),在高频下表现出明显的轮廓增宽。A组和C组谱峰的比例表明,高频谱峰窄化现象比谱峰宽化现象更为普遍,但B组和C组谱峰的比例也很大(共46%)。传统的径向-频率映射仅适用于轮廓变窄现象,很难解释C族脉冲和一部分脉冲展宽的B族脉冲。基于最新版本的扇形束模型,一种宽带发射模型,我们提出,不同的频率依赖的脉冲宽度是不同类型的发射光谱分布在整个发射区域的后果。几何效应预测发射光束收缩和光谱陡峭之间的联系进行了测试,但不赞成。

英文摘要:

The frequency dependence of pulse width is studied for 150 normal pulsars, mostly selected from the European Pulsar Network, for which the 10\% multifrequency pulse widths can be well fit with the Thorsett relationship W_{10}=Aν^μ+W_{\rm 10, min}. The relative fraction of pulse width change between 0.4~GHz and 4.85~GHz, η=(W_{4.85}-W_{0.4})/W_{0.4}, is calculated in terms of the best-fit relationship for each pulsar. It is found that 81 pulsars (54\%) have $η<-10$\% (group A), showing considerable profile narrowing at high frequencies, 40 pulsars (27\%) have $-$10\%$\leqη\leq 10$\% (group B), meaning a marginal change in pulse width, and 29 pulsars (19\%) have $η>10$\% (group C), showing a remarkable profile broadening at high frequencies. The fractions of the group-A and group-C pulsars suggest that the profile narrowing phenomenon at high frequencies is more common than the profile broadening phenomenon, but a large fraction of the group-B and group-C pulsars (a total of 46\%) is also revealed. The group-C pulsars, together with a portion of group-B pulsars with a slight pulse broadening, can hardly be explained using the conventional radius-to-frequency mapping, which only applies to the profile narrowing phenomenon. Based on a recent version of the fan beam model, a type of broadband emission model, we propose that the diverse frequency dependence of pulse width is a consequence of different types of distribution of emission spectra across the emission region. The geometrical effect predicting a link between the emission beam shrinkage and the spectrum steepening is tested but disfavored.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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