Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L Dwarf Companion to the Nearby Solar Analog HR 7672
Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L Dwarf Companion to the Nearby Solar Analog HR 7672
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使用自适应光学穿越棕矮星沙漠：与附近太阳模拟 HR 7672 非常接近的 L 矮星伴侣
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发表时间：
2001
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通讯作者：
R. P. Butler
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作者：
Michael C. Liu;D. Fischer;J. Graham;J. Lloyd;G. Marcy;R. P. Butler
我们发现了一个非常微弱的伴星，它与活跃的太阳类似物HR 7672（HD 190406; GJ 779; 15 Sge）相似。在Gemini-North和Keck II望远镜上使用自适应光学（AO）进行的三个时期的高分辨率成像表明HR 7672 B是一个常见的自行伴星，其分离度为0.“79（14 Au），2.16 μm的通量比为8.6 mag. Use follow-up K-band spectroscopy from Keck AO+NIRSPEC，我们以±1.5子类的不确定性测量L45的光谱类型。这是迄今为止通过直接成像发现的主序星星周围最近的超冷伴星。我们估计初级年龄为1-3 Gyr。假设共演化，伴星很可能是亚恒星，根据理论模型，质量为55-78兆焦。星星表现出长期的径向速度趋势，我们联合收割机径向速度数据和AO成像，设定了一个坚定的（模型无关）下限48兆焦耳。相对于FGK矮星周围104 Au的褐矮星伴星的稀少，HR 7672 B意味着褐矮星伴星确实存在，其距离与我们太阳系中的巨行星相当。它的存在与褐矮星形成为喷射的恒星胚胎的情况不同。此外，由于HR 7672 B的质量可能太大，不可能像人们认为的那样形成在星周盘中，因此它的发现表明，多种物理过程在系外行星系统的外部区域形成。
We have found a very faint companion to the active solar analog HR 7672 (HD 190406; GJ 779; 15 Sge). Three epochs of high-resolution imaging using adaptive optics (AO) at the Gemini-North and Keck II Telescopes demonstrate that HR 7672B is a common proper motion companion, with a separation of 0.″79 (14 AU) and a 2.16 μm flux ratio of 8.6 mag. Using follow-up K-band spectroscopy from Keck AO+NIRSPEC, we measure a spectral type of L45 with an uncertainty of ±1.5 subclasses. This is the closest ultracool companion around a main-sequence star found to date by direct imaging. We estimate that the primary has an age of 1-3 Gyr. Assuming coevality, the companion is most likely substellar, with a mass of 55-78 MJ based on theoretical models. The primary star shows a long-term radial velocity trend, and we combine the radial velocity data and AO imaging to set a firm (model-independent) lower limit of 48 MJ. In contrast to the paucity of brown dwarf companions at ≲4 AU around FGK dwarfs, HR 7672B implies that brown dwarf companions do exist at separations comparable to those of the giant planets in our own solar system. Its presence is at variance with scenarios in which brown dwarfs form as ejected stellar embryos. Moreover, since HR 7672B is likely too massive to have formed in a circumstellar disk as planets are believed to, its discovery suggests that a diversity of physical processes act to populate the outer regions of exoplanetary systems.