Abstract

The emission from the Crab nebula exhibits a significant gamma-ray variability. In this paper we have analyzed this variability in terms of periodicity. Using the pulsar ephemeris constructed from radio data, we have obtained the light curve of the Crab nebula with the suppressed contribution of the pulsar in the energy range 100–300 MeV from August 2008 to March 2020. Using analysis of variance, we have found evidence for a periodicity of flares in the nebula with a period of 49 weeks. The statistical significance of the signal is 0.02 \((2.1\sigma)\) if only the highest peak in the periodogram is taken into account and 0.003 \((2.7\sigma)\) if two peaks, the highest one and the peak at twice the period (98 weeks) that can be caused by the same signal, are taken into account. If the periodicity found is real, then one should expect new periods of enhanced activity of the nebula in August 2021 and 2022.

中文翻译：

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在高能量下从蟹状星云的发射中寻找周期信号

摘要

蟹状星云的发射具有明显的伽马射线可变性。在本文中，我们根据周期性分析了这种可变性。使用从无线电数据构建的脉冲星历表，我们获得了蟹状星云的光曲线，从2008年8月到2020年3月能量范围在100-300 MeV的脉冲星被抑制。使用方差分析，我们发现了证据周期性地爆发星云，周期为49周。如果仅考虑周期图中的最高峰值，则信号的统计显着性为0.02 \（（2.1 \ sigma）\），0.003 \（（2.7 \ sigma）\）如果考虑了两个峰，则最高峰和同一信号可能导致的周期（98周）两倍的峰被考虑在内。如果发现的周期性是真实的，那么人们应该期待在2021年8月和2022年出现新的星云活动增强时期。