发现已知最冷的褐矮星候选者
Discovery of a Candidate for the Coolest Known Brown Dwarf
摘要：
我们已经使用了多历元图像的红外线阵列相机上的斯皮策太空望远镜，以寻找在太阳附近的共同自行的基础上的恒星的亚恒星同伴。通过这项工作，我们发现了白矮星WD 0806-661的一个暗淡的伴星。共动源的投影距离为130”，相当于主星距离（19.2 pc）为2500 AU。如果它是物理上相关的，那么它在4.5微米的绝对星等比已知最暗的T矮星要暗1等，使它成为已知最冷的褐矮星的有力候选者。根据理论演化模型，M4.5和原始年龄（1.5 Gyr）的组合意味着有效温度约为300 K，质量约为7 MJup。这颗白矮星的前身可能有大约2 M太阳的质量，因此可能在出生时就有一个足够大的星周盘来产生一个质量与此相当的伴星。因此，这颗伴星可能是一颗像双星一样形成的褐矮星，也可能是一颗诞生于圆盘中的巨行星，并被动态地分散到更大的轨道上。
英文摘要：
We have used multi-epoch images from the Infrared Array Camera on board the Spitzer Space Telescope to search for substellar companions to stars in the solar neighborhood based on common proper motions. Through this work, we have discovered a faint companion to the white dwarf WD 0806-661. The comoving source has a projected separation of 130", corresponding to 2500 AU at the distance of the primary (19.2 pc). If it is physically associated, then its absolute magnitude at 4.5um is ~1 mag fainter than the faintest known T dwarfs, making it a strong candidate for the coolest known brown dwarf. The combination of M_4.5 and the age of the primary (1.5 Gyr) implies an effective temperature of ~300 K and a mass of ~7 M_Jup according to theoretical evolutionary models. The white dwarf's progenitor likely had a mass of ~2 M_sun, and thus could have been born with a circumstellar disk that was sufficiently massive to produce a companion with this mass. Therefore, the companion could be either a brown dwarf that formed like a binary star or a giant planet that was born within a disk and has been dynamically scattered to a larger orbit.
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