Search for gamma-ray spectral modulations in Galactic pulsars
Search for gamma-ray spectral modulations in Galactic pulsars
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DOI：
10.1088/1475-7516/2018/04/048
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发表时间：
2018-01
影响因子：
6.4
通讯作者：
J. Majumdar;F. Calore;D. Horns
中科院分区：
文献类型：
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作者：
J. Majumdar;F. Calore;D. Horns
标准模型的合理扩展预测了超轻和基本赝标量粒子（例如，轴子或类轴子粒子：ALP）。与轴子的普里马科夫效应类似，ALP可以与光子混合，因此可以在实验室实验和天体物理观测中寻找。在这里，我们寻找能量依赖的调制的高能伽马射线光谱，告诉故事签名的光子ALP混合。为此，我们分析的数据记录与费米-LAT从银河系的恒星选择有一个视线交叉螺旋臂在一个大的俯仰角。大规模的银河磁场的痕迹螺旋臂的形状，这样一个相当大的光子ALP转换概率预计所考虑的来源。对于附近的船帆座脉冲星，能谱可以很好地描述为平滑模型谱（具有次指数截止的幂律），而对于六个选定的银河系脉冲星，与平滑模型谱相比，ALP参数的共同拟合提高了拟合优度，显著性为4.6 σ。我们确定质量ma和耦合gaγγ的最可能值为ma=（3.6−0.2 stat.+ 0.5静态± 0.2系统）neV和gaγγ=（2.3− 0.4 stat.+ 0.3静态± 0.4系统）× 10−10 GeV−1。在误差预算中，我们考虑了仪器效应、所采用的银河磁场模型的标度（± 20%）以及单个源距离的不确定性。最适合的参数是由一个因素的103倍以上的最佳限制太阳能ALP生成与CAST日光镜，虽然已知的修改的光子ALP混合在高密度的太阳能环境中可以提供一个合理的解释日光镜约束和指示之间的明显的紧张局势的光子ALP混合在这里报道。
Well-motivated extensions of the standard model predict ultra-light and fundamental pseudo-scalar particles (e.g., axions or axion-like particles: ALPs). Similarly to the Primakoff-effect for axions, ALPs can mix with photons and consequently be searched for in laboratory experiments and with astrophysical observations. Here, we search for energy-dependent modulations of high-energy gamma-ray spectra that are tell-tale signatures of photon-ALPs mixing. To this end, we analyze the data recorded with the Fermi-LAT from Galactic pulsars selected to have a line of sight crossing spiral arms at a large pitch angle. The large-scale Galactic magnetic field traces the shape of spiral arms, such that a sizable photon-ALP conversion probability is expected for the sources considered. For the nearby Vela pulsar, the energy spectrum is well described by a smooth model spectrum (a power-law with a sub-exponential cut-off) while for the six selected Galactic pulsars, a common fit of the ALPs parameters improves the goodness of fit in comparison to a smooth model spectrum with a significance of 4.6 σ. We determine the most-likely values for mass ma and coupling gaγγ to be ma=(3.6−0.2 stat.+0.5 stat.± 0.2syst. ) neV and gaγγ=(2.3−0.4stat.+0.3 stat.± 0.4syst.)× 10−10 GeV−1. In the error budget, we consider instrumental effects, scaling of the adopted Galactic magnetic field model (± 20 %), and uncertainties on the distance of individual sources. The best-fit parameters are by a factor of ≈ 3 larger than the current best limit on solar ALPs generation obtained with the CAST helioscope, although known modifications of the photon-ALP mixing in the high density solar environment could provide a plausible explanation for the apparent tension between the helioscope bound and the indication for photon-ALPs mixing reported here.