CFBDS J005910 .90-011401.3：达到T-Y褐矮星转变？
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition?
摘要：
我们报告了CFBDS J005910.90-011401.3（以下简称CFBDS 0059）的发现，这是迄今为止发现的最冷的棕矮星。我们使用加拿大-法国-夏威夷望远镜（CFHT）的i'和z'图像发现了CFBDS 0059，并提供了光学和近红外测光，凯克激光导星自适应光学成像和完整的近红外光谱，从1.0到2.2 $μ$ m。对CFBDS 0059和ULAS J003402.77-005206.7（以下简称ULAS 0034）的近红外光谱进行了比较，发现CFBDS 0059的温度要低50+/-15K。我们估计Teff ~ 620 K的温度和log g ~ 4.75的重力。演化模型将这些参数转化为1-5 Gyr的年龄和1 - 5 -30 M_Jup的质量。我们估计测光距离约为13 pc，这使得CFBDS 0059很容易达到精确的视差测量。它的大自行表明它属于薄圆盘的老年群体。CFBDS 0059和ULAS J 0034的光谱均显示出$H$带通量峰蓝色侧的宽氨带的可能吸收。如果像我们所预料的那样，这种特征在更低的有效温度下进一步加深，它的出现将成为T光谱类和新的Y光谱类型之间过渡的自然断点。CFBDS 0059和ULAS J 0034将是第一个Y 0矮星。
英文摘要：
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii Telescope (CFHT), and present optical and near-infrared photometry, Keck laser guide star adaptive optics imaging, and a complete near-infrared spectrum, from 1.0 to 2.2 $μ$m. A side to side comparison of the near-infrared spectra of CFBDS0059 and ULAS J003402.77-005206.7 (hereafter ULAS0034), previously the coolest known brown dwarf, indicates that CFBDS0059 is ~50+/-15K cooler. We estimate a temperature of Teff ~ 620K and gravity of log g ~ 4.75. Evolutionary models translate these parameters into an age of 1-5 Gyr and a mass of 15-30 M_Jup. We estimate a photometric distance of ~13pc, which puts CFBDS0059 within easy reach of accurate parallax measurements. Its large proper motion suggests membership in the older population of the thin disk. The spectra of both CFBDS0059 and ULAS J0034 shows probable absorption by a wide ammonia band on the blue side of the $H$-band flux peak. If, as we expect, that feature deepens further for still lower effective temperatures, its appearance will become a natural breakpoint for the transition between the T spectral class and the new Y spectral type. CFBDS0059 and ULAS J0034 would then be the first Y0 dwarfs.
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