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arXiv 1503.00744astro-ph.HE
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用FERMI光谱仪测试耗散磁层模型光变曲线和光谱

Testing dissipative magnetosphere model light curves and spectra with FERMI pulsars

Gabriele Brambilla, Constantinos Kalapotharakos, Alice K. Harding, Demosthenes Kazanas

摘要:

我们探索了Kalapotharakos等人(2014)引入的耗散脉冲星磁层模型的发射特性,将其高能光变曲线和光谱与费米LAT收集的数据进行了比较。磁层结构被假定为接近无力解。假设光圆柱内部的加速电场可以忽略不计,而光圆柱外部的加速电场则以有限的电导率(σ)重新缩放。在我们的方法中,我们计算出相应的高能量的发射,通过整合的轨道的测试粒子,起源于恒星表面,同时考虑到加速电场分量和辐射反作用力。首先,我们探索的参数空间假设不同的值集的恒星磁场,恒星周期和电导率。结果表明,该模型的一般性质与观测到的年轻γ射线双星的发射特性,包括相位分辨谱的特征,符合得很好。其次,我们找到模型参数,适合每个脉冲星属于一组的八个明亮的恒星,有一个公布的相位分辨光谱。最能描述这一组中每个脉冲星的σ值显示出随着自旋下降速率$(\dot{E})$的增加而增加,随着脉冲星年龄的减少,如果成对级联提供磁层电导率的话。最后,我们探讨了我们的分析的局限性,并提出了未来改进此类模型的方向。

英文摘要:

We explore the emission properties of a dissipative pulsar magnetosphere model introduced by Kalapotharakos et al. (2014), comparing its high energy light curves and spectra, due to curvature radiation, with data collected by the Fermi LAT. The magnetosphere structure is assumed to be near the force-free solution. The accelerating electric field, inside the light-cylinder, is assumed to be negligible, while outside the light-cylinder it rescales with a finite conductivity (σ). In our approach we calculate the corresponding high energy emission by integrating the trajectories of test particles that originate from the stellar surface, taking into account both the accelerating electric field components and the radiation reaction forces. First we explore the parameter space assuming different value sets for the stellar magnetic field, stellar period, and conductivity. We show that the general properties of the model are in a good agreement with observed emission characteristics of young γ-ray pulsars, including features of the phase resolved spectra. Second we find model parameters that fit each pulsar belonging to a group of eight bright pulsars that have a published phase-resolved spectrum. The σ values that best describe each of the pulsars in this group show an increase with the spin-down rate $(\dot{E})$ and a decrease with the pulsar age, expected if pair cascades are providing the magnetospheric conductivity. Finally, we explore the limits of our analysis and suggest future directions for improving such models.

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