We report on orbital modulation of the 100-600 MeV gamma-ray emission of the $P_{\rm B}=4.6$ hr millisecond pulsar binary PSR J2339$-$0533 using 11 yr of Fermi Large Area Telescope data. The modulation has high significance (chance probability $p\approx 10^{-7}$), is approximately sinusoidal, peaks near pulsar superior conjunction, and is detected only in the low-energy 100-600 MeV band. The modulation is confined to the on-pulse interval, suggesting that the variation is in the 2.9-ms pulsed signal itself. This contrasts with the few other known systems exhibiting GeV orbital modulations, as these are unpulsed and generally associated with beamed emission from an intrabinary shock. The origin of the modulated pulsed signal is not yet clear, although we describe several scenarios, including Compton upscattering of photons from the heated companion. This would require high coherence in the striped pulsar wind.

中文翻译：

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来自 PSR J2339-0533 的伽马射线的轨道调制

我们使用 11 年的费米大面积望远镜数据报告了 $P_{\rm B}=4.6$ hr 毫秒脉冲星双星 PSR J2339$-$0533 的 100-600 MeV 伽马射线发射的轨道调制。调制具有很高的显着性（机会概率 $p\approx 10^{-7}$），近似正弦波，在脉冲星上会合附近达到峰值，并且仅在低能量 100-600 MeV 波段检测到。调制仅限于脉冲间隔，表明变化发生在 2.9 毫秒脉冲信号本身。这与表现出 GeV 轨道调制的少数其他已知系统形成对比，因为这些系统是非脉冲的，并且通常与来自双星内部激波的光束发射有关。调制脉冲信号的起源尚不清楚，尽管我们描述了几种情况，包括来自加热伴星的光子的康普顿向上散射。