Title: Polarised radio pulsations from a new T dwarf binary Show Chinese title

Title: 极化射电脉动来自一个新的T型矮星双星

Abstract: Brown dwarfs display Jupiter-like auroral phenomena such as magnetospheric H$\alpha$ emission and coherent radio emission. Coherent radio emission is a probe of magnetospheric acceleration mechanisms and provides a direct measurement of the magnetic field strength at the emitter's location, both of which are difficult to access by other means. Observations of the coldest brown dwarfs (spectral types T and Y) are particularly interesting as their magnetospheric phenomena may be very similar to those in gas-giant exoplanets. Here we present 144 MHz radio and infrared adaptive optics observations of the brown dwarf WISEP J101905.63+652954.2 made using the LOFAR and Keck telescopes respectively. The radio data shows pulsed highly circularly polarised emission which yields a rotation rate of $0.32\pm0.03$ hr$^{-1}$. The infrared imaging reveals the source to be a binary with a projected separation of $423.0\pm1.6$ mas between components of spectral type T5.$5\pm0.5$ and T7.$0\pm0.5$. With a simple "toy model" we show that the radio emission can in principle be powered by the interaction between the two dwarfs with a mass-loss rates of at least $25$ times the Jovian value. WISEP J101905.63+652954.2 is interesting because it is the first pulsed methane dwarf detected in a low radio-frequency search. Unlike previous gigahertz-frequency searches that were only sensitive to objects with kiloGauss fields, our low-frequency search is sensitive to surface magnetic fields of $\approx 50$ Gauss and above which might reveal the coldest radio-loud objects down to planetary mass-scales. Show Chinese abstract

Abstract: 棕矮星表现出类似木星的极光现象，如磁层H$\alpha$发射和相干射电发射。相干射电发射是磁层加速机制的探测手段，并能直接测量发射源位置的磁场强度，这两者通过其他方法都难以获取。对最冷的棕矮星（光谱类型T和Y）的观测尤其有趣，因为它们的磁层现象可能与气态巨行星系外行星非常相似。在这里，我们分别使用LOFAR和Keck望远镜对棕矮星WISEP J101905.63+652954.2进行了144 MHz的射电和红外自适应光学观测。射电数据显示出脉冲的高圆偏振发射，这给出了旋转速率为$0.32\pm0.03$小时$^{-1}$。红外成像显示该天体是一个双星系统，光谱类型为T5和$5\pm0.5$的组分之间的投影距离为$423.0\pm1.6$毫角秒。T7。$0\pm0.5$。通过一个简单的“玩具模型”，我们表明射电发射原则上可以由两个矮星之间的相互作用提供，其质量损失率至少为$25$倍于木星的值。WISEP J101905.63+652954.2很有趣，因为它是在低射频搜索中首次检测到的脉冲甲烷矮星。 与之前仅对具有千高斯磁场的物体敏感的吉赫兹频率搜索不同，我们的低频搜索对表面磁场为$\approx 50$高斯及以上的物体敏感，这可能会揭示出温度最低的射电明亮物体，甚至达到行星质量尺度。