Axion dark matter (DM) may convert to radio-frequency electromagnetic radiation in the strong magnetic fields around neutron stars. The radio signature of such a process would be an ultra-narrow spectral peak at a frequency determined by the mass of the axion particle. We analyze data we collected from the Robert C. Byrd Green Bank Telescope in the L-band and the Effelsberg 100-m Telescope in the L-Band and S-band from a number of sources expected to produce bright signals of axion-photon conversion, including the Galactic Center of the Milky Way and the nearby isolated neutron stars RX J0720.4$-$3125andRXJ0806.4$-$4123. We find no evidence for axion DM and are able to {set constraints on the existence of axion DM in the highly motivated mass range between $$5-11 $\mu$eV with the strongest constraints to-date on axions in the $$10-11 $\mu$eV range.

中文翻译：

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Green Bank和Effelsberg射电望远镜在中子星磁层中寻找轴突暗物质转换

轴突暗物质（DM）可能在中子星周围的强磁场中转换为射频电磁辐射。这种过程的无线电信号将是一个超窄谱峰，其频率由轴突粒子的质量决定。我们分析了从L波段的Robert C. Byrd Green Bank望远镜和L波段和S波段的Effelsberg 100-m望远镜收集到的数据，这些数据来自有望产生轴突-光子转换明亮信号的多种来源，包括银河系的银河中心和附近的孤立中子星RX J0720.4 $-$3125\mathrm{一种}ñd\mathrm{[R}XĴ0806.4$-4123美元。我们找不到轴力DM的证据，并且能够{在5-11美元之间的高动力质量范围内设置轴力DM的存在限制。$\mu$电动势，迄今为止对轴的约束最强，在10-11美元 $\mu$eV范围。