We calculate the axion emission rate from reactions involving thermal pions in matter encountered in supernovae and neutron star mergers, identify unique spectral features, and explore their implications for astrophysics and particle physics. We find that it is about 2–5 times larger than nucleon-nucleon bremsstrahlung, which in past studies was considered to be the dominant process. The axion spectrum is also found be much harder. Together, the larger rates and higher axion energies imply a stronger bound on the mass of the QCD axion and better prospects for direct detection in a large underground neutrino detector from a nearby galactic supernova.

中文翻译：

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超新星轴增强发射及其意义

我们根据超新星和中子星合并中遇到的物质中涉及热离子的反应计算轴突发射速率，确定独特的光谱特征，并探讨它们对天体物理学和粒子物理学的影响。我们发现它比核子-核nucleo致大约2至5倍，后者在过去的研究中被认为是主要过程。还发现轴突光谱要困难得多。总的来说，更高的速率和更高的轴突能量意味着更强的QCD轴突束缚，以及从附近银河超新星的大型地下中微子探测器中直接探测的更好前景。