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arXiv 1406.2767astro-ph.HE
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Gamma-Ray脉冲星中磁对产生的透明性

Magnetic Pair Creation Transparency in Gamma-Ray Pulsars

Sarah A. Story, Matthew G. Baring

摘要:

磁对的产生$γ\to e^+e^-$在过去的三十年里一直是射电脉冲星范例的核心,也是伽马射线脉冲星极帽模型的核心。费米伽马射线脉冲星的数量现在超过140个来源,并定义了费米科学遗产的重要组成部分。在已确定的总体特征中,在1- 10 GeV范围内,它们的谱中经常发生指数转换。这些变化太过平缓,不可能是脉冲星内磁层的强磁场产生的磁对。通过要求由这种单光子对产生引起的微不足道的光子衰减,费米介子的这些翻转的能量可以用来计算GeV带发射的典型高度的下限。本文探讨了这种对透明度的限制下的营业额的能量,并更新早期的高度约束的测定已部署在各种费米脉冲星的文件。对于低空发射地点,广义相对论的影响是很重要的。旋转像差的影响也进行了探讨,并发现在低海拔地区是小的,除了附近的磁极。对于年轻的费米脉冲星群体,高度界限通常在2-7个恒星半径的范围内,并提供了关于不具有双峰脉冲轮廓的无线电安静脉冲星的发射高度的关键信息。蟹状星云脉冲星的边界在更高的高度,MAGIC的推定探测到350-400 GeV,这意味着发射区的下限为310公里,即,大约是光圆柱半径的20%。这些结果也被扩展到超临界场域,在那里发现,在磁星的发射起源低于约10恒星半径将不会出现在费米-LAT带。

英文摘要:

Magnetic pair creation $γ\to e^+e^-$ has been at the core of radio pulsar paradigms and central to polar cap models of gamma-ray pulsars for over three decades. The Fermi gamma-ray pulsar population now exceeds 140 sources and has defined an important part of Fermi's science legacy. Among the population characteristics well established is the common occurrence of exponential turnovers in their spectra in the 1--10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres. By demanding insignificant photon attenuation precipitated by such single-photon pair creation, the energies of these turnovers for Fermi pulsars can be used to compute lower bounds for the typical altitude of GeV band emission. This paper explores such pair transparency constraints below the turnover energy, and updates earlier altitude bound determinations of that have been deployed in various Fermi pulsar papers. For low altitude emission locales, general relativistic influences are found to be important. Rotational aberration influences are also explored, and are found to be small at low altitudes, except near the magnetic pole. The altitude bounds are typically in the range of 2-7 stellar radii for the young Fermi pulsar population, and provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. The bound for the Crab pulsar is at a much higher altitude, with the putative detection by MAGIC out to 350-400 GeV implying a lower bound of 310km to the emission region, i.e., approximately 20% of the light cylinder radius. These results are also extended to the super-critical field domain, where it is found that emission in magnetars originating below around 10 stellar radii will not appear in the Fermi-LAT band.

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