Probing gamma-ray emissions of Fermi-LAT pulsars with a non-stationary outer gap model
Probing gamma-ray emissions of Fermi-LAT pulsars with a non-stationary outer gap model
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用非平稳外间隙模型探测 Fermi-LAT 脉冲星的伽马射线发射
DOI：
10.1093/mnras/stv2612
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发表时间：
2015-11
影响因子：
--
通讯作者：
Cheng K.S.
中科院分区：
文献类型：
--
作者：
Jumpei Takata;Ng C. W;Cheng K.S.
我们探讨了脉冲星磁层中伽马射线发射过程的非平稳外间隙情景。电子/正电子沿着磁力线迁移，从外部/内部边界进入外部间隙，激活成对产生级联和高能发射过程。在我们的模型中，粒子在间隙边界处的注入速率是控制间隙结构和伽马能谱性质的关键物理量。我们的模型假设注入速度是时变的，观测到的伽玛射线谱是不同间隙结构在间隙边界处不同注入速度的辐射的叠加。假设粒子注入速率的幂律分布叠加得到的计算谱可以再现费米- lat观测到的伽玛射线谱的次指数截止特征。用该模型拟合了43颗中青年脉冲星和14颗毫秒脉冲星的相位平均光谱。我们的研究结果表明：(1)对于自旋下降功率较大的脉冲星，在间隙边界处更频繁地有较大的粒子注入；(2)注入速率远小于Goldreich-Julian值的外间隙产生观测到的$ bbb10 $GeV发射。Fermi-LAT伽玛射线脉冲星表明：(1)观测到的截止能量以下的伽玛射线能谱在自旋下降速率较高的脉冲星中趋于柔和；(2)在较高的能带中第二峰更为突出。根据拟合的结果，我们描述了这些观测性质的可能的理论解释。我们还简要讨论了蟹状毫秒脉冲星，它显示出相位对准的射电和伽马射线脉冲。
We explore a non-stationary outer gap scenario for gamma-ray emission process in pulsar magnetosphere. Electrons/positrons that migrate along the magnetic field line and enter the outer gap from the outer/inner boundaries activate the pair-creation cascade and high-energy emission process. In our model, the rate of the particle injection at the gap boundaries is key physical quantity to control the gap structure and properties of the gamma-ray spectrum. Our model assumes that the injection rate is time variable and the observed gamma-ray spectrum are superposition of the emissions from different gap structures with different injection rates at the gap boundaries. The calculated spectrum superposed by assuming power law distribution of the particle injection rate can reproduce sub-exponential cut-off feature in the gamma-ray spectrum observed by Fermi-LAT. We fit the phase-averaged spectra for 43 young/middle-age pulsars and 14 millisecond pulsars with the model. Our results imply that (1) a larger particle injection at the gap boundaries is more frequent for the pulsar with a larger spin down power and (2) outer gap with an injection rate much smaller than the Goldreich-Julian value produces observe $>10$GeV emissions. Fermi-LAT gamma-ray pulsars show that (i) the observed gamma-ray spectrum below cut-off energy tends to be softer for the pulsar with a higher spin down rate and (ii) the second peak is more prominent in higher energy bands. Based on the results of the fitting, we describe possible theoretical interpretations for these observational properties. We also briefly discuss Crab-like millisecond pulsars that show phase-aligned radio and gamma-ray pulses.
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DOI：
10.1086/508317
发表时间：
2006-08
期刊：
The Astrophysical Journal
影响因子：
--
作者：
K. Hirotani
通讯作者：
K. Hirotani
DOI：
10.1088/0004-637x/727/2/123
发表时间：
2010-09
期刊：
The Astrophysical Journal
影响因子：
--
作者：
K. Watters;R. Romani
通讯作者：
K. Watters;R. Romani
DOI：
10.1088/2041-8205/797/2/l13
发表时间：
2014-10
期刊：
The Astrophysical Journal Letters
影响因子：
--
作者：
G. Leung;J. Takata;C. Ng;A. Kong;P. Tam;C. Hui;K. Cheng
通讯作者：
G. Leung;J. Takata;C. Ng;A. Kong;P. Tam;C. Hui;K. Cheng
DOI：
10.1086/508253
发表时间：
2006
期刊：
--
影响因子：
--
作者：
H. S. Knight;M. Bailes
通讯作者：
H. S. Knight;M. Bailes
影响因子：
8.6
作者：
A. Gruzinov
通讯作者：
A. Gruzinov