COSMIC-RAY POSITRONS FROM MILLISECOND PULSARS
COSMIC-RAY POSITRONS FROM MILLISECOND PULSARS
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DOI：
10.1088/0004-637x/807/2/130
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发表时间：
2015-06
期刊：
影响因子：
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通讯作者：
C. Venter;A. Kopp;A. Harding;P. Gonthier;I. Büsching
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作者：
C. Venter;A. Kopp;A. Harding;P. Gonthier;I. Büsching
费米大面积望远镜对γ射线毫秒脉冲星（MSP）光变曲线的观测表明，它们的磁层中存在大量的电子对产生，而不仅仅是年轻的脉冲星。这种对级联可能是银河系电子和正电子的主要来源，有助于观察到正电子通量高于~10 GeV。费米还发现了许多新的 MSP，影响了银河系恒星种群模型。我们研究了银河 MSP 对地球宇宙射线电子和正电子通量的贡献。我们的群体合成代码预测了当今 MSP 的源属性。我们通过调用偏移偶极子磁场来模拟它们的配对光谱。我们还考虑了黑寡妇（BW）和红背（RB）系统中强烈的二元内激波进一步加速到几个 TeV 能量的正电子和电子。由于MSP没有被脉冲星风星云或超新星壳包围，我们假设这些对自由逃逸并仅在星系间介质中遭受损失。我们计算地球上的传输对光谱，跟踪它们在银河系中的扩散和能量损失。预测的粒子通量随着磁极帽的非零偏移而增加。来自 MSP 磁层的对级联对阿尔法磁谱仪、PAMELA 和费米测量的轻子通量仅产生大约几十 GeV 的适度贡献，之后该分量就被切断。然而，BW 和 RB 的贡献可能在数十 TeV 时达到百分之几十的水平，具体取决于模型参数。
Observations by the Fermi Large Area Telescope of γ-ray millisecond pulsar (MSP) light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ∼10 GeV. Fermi has also uncovered many new MSPs, impacting Galactic stellar population models. We investigate the contribution of Galactic MSPs to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day MSPs. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow (BW) and redback (RB) systems. Since MSPs are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of MSPs are only modest contributors around a few tens of GeV to the lepton fluxes measured by the Alpha Magnetic Spectrometer, PAMELA, and Fermi, after which this component cuts off. The contribution by BWs and RBs may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters.