Axion-like particles (ALPs) coupled to nucleons can be efficiently produced in the interior of protoneutron stars (PNS) during supernova (SN) explosions. If these ALPs are also coupled to photons they can convert into gamma rays in the Galactic magnetic field. This SN-induced gamma-ray burst can be observable by gamma-ray telescopes like Fermi-LAT if the SN is in the field of view of the detector. We show that the observable gamma-ray spectrum is sensitive to the production processes in the SN core. In particular, if the nucleon-nucleon bremsstrahlung is the dominant axion production channel, one expects a thermal spectrum with average energy E _a ≃ 50 MeV. In this case the gamma-ray spectrum observation allows for the reconstruction of the PNS temperature. In case of a sizable pion abundance in the SN core, one expects a second spectral component peaked at E _a ≃ 200 MeV due to axion pionic processes. We demonstrate that, through a dedicated LAT analysis, we can detect the presence of this pionic contribution, showing that the detection of the spectral shape of the gamma-ray signal represents a unique probe of the pion abundance in the PNS.

中文翻译：

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用 γ 射线轴测镜探测质子子星


在超新星 （SN） 爆炸期间，与核子耦合的轴状粒子 （ALP） 可以在质子原子星 （PNS） 的内部有效地产生。如果这些 ALP 也与光子耦合，它们就可以在银河磁场中转化为伽马射线。如果 SN 位于探测器的视野内，则这种 SN 诱导的伽马射线暴可以被 Fermi-LAT 等伽马射线望远镜观察到。我们表明，可观测的伽马射线光谱对 SN 核心中的生产过程很敏感。特别是，如果核子-核子轫致辐射是主要的轴子产生通道，则预计热谱平均能量 E _a ≃ 50 MeV。在这种情况下，伽马射线光谱观测允许重建 PNS 温度。如果 SN 核心中存在相当大的 pion 丰度，则由于轴子 pionic 过程，预计第二个光谱分量在 E _a ≃ 200 MeV 处达到峰值。我们证明，通过专门的 LAT 分析，我们可以检测到这种 pionic 贡献的存在，表明对 γ 射线信号光谱形状的检测代表了 PNS 中 pion 丰度的独特探针。