恒星周围旋转纳米金刚石的异常微波发射
Anomalous microwave emission from spinning nanodiamonds around stars
摘要：
几个星际环境产生“异常微波发射”，亮度峰值在几十千兆赫频率。这种辐射的来源尚不确定--快速旋转的纳米粒子可能会发出电偶极辐射，但现在发现作为载体的多环芳烃与银河信号无关。困难的是在长的视线上识别共空间源。在这里，我们确定在三个原行星盘异常微波发射。这些是唯一已知的系统，主机氢化纳米金刚石，与非常常见的检测多环芳烃。光谱学将纳米金刚石定位在靠近主星的位置，在物理限制的温度下。通过开发圆盘模型，我们用半径为0.75-1.1纳米的钻石重现了排放量，其碳预算小于或等于1%-2%。微波辐射与恒星光度的比值近似恒定，这使得纳米钻石无处不在，但在许多恒星系统中的辐射低于检测阈值。这可以将这些发现与太阳系陨石中发现的类似大小的钻石统一起来。由于纳米金刚石光谱吸收在星际视线中可见，这些粒子也是产生星系尺度异常微波发射的候选者。
英文摘要：
Several interstellar environments produce 'anomalous microwave emission', with brightness-peaks at tens-of-gigahertz frequencies. The emission's origins are uncertain - rapidly-spinning nano-particles could emit electric-dipole radiation, but polycyclic aromatic hydrocarbons proposed as the carrier are now found not to correlate with Galactic signals. The difficulty is to identify co-spatial sources over long lines of sight. Here we identify anomalous microwave emission in three proto-planetary discs. These are the only known systems that host hydrogenated nano-diamonds, in contrast to very common detection of polycyclic aromatic hydrocarbons. Spectroscopy locates the nano-diamonds close to the host-stars, at physically-constrained temperatures. Developing disc models, we reproduce the emission with diamonds 0.75-1.1 nanometres in radius, holding less than or equal to 1-2 per cent of the carbon budget. The microwave-emission:stellar-luminosity ratios are approximately constant, allowing nano-diamonds to be ubiquitous but emitting below detection thresholds in many star-systems. This can unify the findings with similar-sized diamonds found within solar system meteorites. As nano-diamond spectral absorption is seen in interstellar sightlines, these particles are also a candidate for generating galaxy-scale anomalous microwave emission.
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