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arXiv 0804.0220astro-ph
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两颗中年邻近脉冲星引起的Cosmic Ray正电子各向异性?

A Cosmic Ray Positron Anisotropy due to Two Middle-Aged, Nearby Pulsars?

I. Buesching, O. C. de Jager, M. S. Potgieter, C. Venter

摘要:

Geminga和B 0656 +14是最近的恒星,其特征年龄在10万年到100万年之间。目前,它们都具有3e 34 erg/s量级的自旋功率。这些恒星的风很可能为脉冲星风星云(PWNe)提供了动力,脉冲星风星云在恒星诞生后不到10万年就解体了。假设被脉冲星加速的轻子粒子被限制在PWNe中,并在PWNe破裂时释放到星际介质中,我们证明,根据脉冲星的参数,这两颗脉冲星对局域宇宙线正电子谱的贡献不可忽略,它们可能是几GeV以上的主要贡献者. Geminga和B 0656 +14之间相对较小的角距离因此意味着在这些能量下局部CR正电子通量的各向异性。我们计算了这些脉冲星对局部观测到的CR电子和正电子谱的贡献,它依赖于脉冲星的诞生周期和局部CR扩散系数的大小。我们进一步给出了局部CR正电子通量的预期各向异性的估计。我们的计算表明,在我们的模型框架内,本地CR轻子谱对Geminga和B 0656 +14的脉冲星参数施加了约束,特别是脉冲星诞生时的周期,以及CR轻子的本地星际扩散系数。

英文摘要:

Geminga and B0656+14 are the closest pulsars with characteristic ages in the ran ge of 100 kyr to 1 Myr. They both have spindown powers of the order 3e34 erg/s at present. The winds of these pulsars had most probably powered pulsar wind nebulae (PWNe) that broke up less than about 100 kyr after the birth of the pulsars. Assuming that leptonic particles accelerated by the pulsars were confined in th e PWNe and were released into the interstellar medium (ISM) on breakup of the PW Ne, we show that, depending on the pulsar parameters, both pulsars make a non-ne gligible contribution to the local cosmic ray (CR) positron spectrum, and they m ay be the main contributors above several GeV. The relatively small angular dist ance between Geminga and B0656+14 thus implies an anisotropy in the local CR po sitron flux at these energies. We calculate the contribution of these pulsars to the locally observed CR electr on and positron spectra depending on the pulsar birth period and the magnitude o f the local CR diffusion coefficient. We further give an estimate of the expecte d anisotropy in the local CR positron flux. Our calculations show that within the framework of our model, the local CR posit ron spectrum imposes constraints on pulsar parameters for Geminga and B0656+14, notably the pulsar period at birth, and also the local interstellar diffusion co efficient for CR leptons.

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