标题： 一个在开普勒中表现出单次凌日的长周期亚恒星天体 显示英文标题

标题： A long-period substellar object exhibiting a single transit in Kepler

摘要： 我们报告在稍有演化的F型恒星KIC4918810的开普勒数据中检测到一个单一的凌星信号。 凌星持续时间约为45小时，虽然轨道周期（$P\sim10$年）没有得到很好约束，但它是在已知凌星伴星中周期最长的之一。 我们计算出凌星天体的大小为$R_P = 0.910$ $R_J$ 。 此类大小的天体密度相差数量级，涵盖从土星（$0.3$ $M_J$ ）到超过氢燃烧极限的恒星（约80$M_J$）之间的质量。 径向速度观测表明，该伴星不太可能是恒星。 质量后验分布是双峰的，表明质量可能是约0.24 $M_J$ 或约26 $M_J$。 持续的光谱监测应该能够将质量限制为行星质量，或者检测轨道运动，后者将产生一个具有测量质量、半径和年龄的基准长周期棕矮星。 显示英文摘要

摘要： We report the detection of a single transit-like signal in the Kepler data of the slightly evolved F star KIC4918810. The transit duration is ~45 hours, and while the orbital period ($P\sim10$ years) is not well constrained, it is one of the longest among companions known to transit. We calculate the size of the transiting object to be $R_P = 0.910$ $R_J$. Objects of this size vary by orders of magnitude in their densities, encompassing masses between that of Saturn ($0.3$ $M_J$) and stars above the hydrogen-burning limit (~80 $M_J$). Radial-velocity observations reveal that the companion is unlikely to be a star. The mass posterior is bimodal, indicating a mass of either ~0.24 $M_J$ or ~26 $M_J$. Continued spectroscopic monitoring should either constrain the mass to be planetary or detect the orbital motion, the latter of which would yield a benchmark long-period brown dwarf with a measured mass, radius, and age.