标题： 吸积轴子星的射电波段线条 显示英文标题

标题： Radio Lines from accreting Axion Stars

摘要： 类轴子粒子，我们称之为轴子，可以构成缺失的暗物质，并可能形成次结构，例如微团和轴子星。 我们获得了来自银河系宿主微团的轴子星质量分布，并发现大量达到衰变质量（由轴子-光子耦合设定的关键质量）的轴子星。 达到衰变质量的轴子星可以通过其宿主微团吸收周围的轴子，无论是通过还是直接地，随后通过参数共振将其转化为射电光子。 我们展示了这种吸积提供了可观测信号，提出了两种情景：1）背景暗物质通过微团的外部吸积，2）孤立系统通过微团直接对其核心的内部吸积。 发射的射电光子能量几乎单色，在轴子质量的一半左右。 这种轴子星发出的射电信号提供了一个独特的寻找轴子的机会，克服了广泛的射电背景。 我们估计了每个轴子质量下的预期射线通量密度，以约束轴子-光子耦合$g_{a\gamma\gamma}$，并发现由此产生的线状通量密度足够强，可以在LOFAR、FAST、ALMA以及即将推出的SKA等射电望远镜中观测到。 我们可以根据轴子星吸积模型的不同，将轴子-光子耦合限制到$g_{a\gamma\gamma} \simeq 10^{-12} - 10^{-11}\,{\rm GeV}^{-1}$，甚至达到$10^{-13}\,{\rm GeV}^{-1}$，覆盖轴子质量范围$m_a\simeq 10^{-7} - 10^{-2}\,{\rm eV}$。 从另一个角度来看，这个射电信号可能是对应质量轴子的一个强烈暗示，也是我们银河系内轴子星的一个强烈暗示。 显示英文摘要

摘要： Axion-like particles, which we call axions, can compose the missing dark matter and may form substructures such as miniclusters and axion stars. We obtain the mass distributions of axion stars derived from their host miniclusters in our galaxy and find a significant number of axion stars reaching the decay mass, the critical mass set by the axion-photon coupling. Axion stars that have reached the decay mass can accrete surrounding axions either via or directly from their host miniclusters, subsequently converting them into radio photons through parametric resonance. We demonstrate that this accretion provides observable signals by proposing two scenarios: 1) external accretion of background dark matter occurring via miniclusters, and 2) internal accretion of isolated systems occurring directly from the minicluster onto its core. The emitted radio photons are nearly monochromatic with energies around the half of the axion mass. The radio-line signal emanating from such axion stars provides a distinctive opportunity searching for axions, overcoming the widespread radio backgrounds. We estimate the expected radio-line flux density to constrain the axion-photon coupling $g_{a\gamma\gamma}$ at each axion mass and find that the resultant line flux density is strong enough to be observed in radio telescopes such as LOFAR, FAST, ALMA, and upcoming SKA. We can constrain the axion-photon coupling down to $g_{a\gamma\gamma} \simeq 10^{-12} - 10^{-11}\,{\rm GeV}^{-1}$, reaching even $10^{-13}\,{\rm GeV}^{-1}$ depending on the accretion models of axion stars, over an axion mass range of $m_a\simeq 10^{-7} - 10^{-2}\,{\rm eV}$. From a different perspective, this radio-line signal could be a strong hint of an axion at the corresponding mass and also of axion stars within our galaxy.