arXiv 1008.19832010-08-23astro-ph.SRastro-ph.EP

GJ 758的褐矮星/行星质量伴星的高对比度3.8微米成像

High-Contrast 3.8 Micron Imaging Of The Brown Dwarf/Planet-Mass Companion to GJ 758

Thayne Currie, Vanessa Bailey, Daniel Fabrycky, Ruth Murray-Clay, Timothy Rodigas, Phil Hinz

备注：: 14 pages, 3 figures. Accepted for publication in The Astrophysical Journal Letters
DOI：: 10.1088/2041-8205/721/2/L177

摘要：

我们展示了附近恒星GJ 758的L'波段（3.8 $μm$）MMT/Clio高对比度成像数据，Thalmann等人（2009）最近报道了它有一个-可能是两个-微弱的伴星（分别为GJ 758 B和"C”）。GJ 758 B在两个不同的数据集中被检测到。此外，我们报告了一个\textit{possible}检测的对象确定的Thalmann等人作为"GJ 758 C”在我们更敏感的数据集，虽然它可能是一个残留的斑点。然而，如果它是与Thalmann等人报告的相同的物体，它就不可能是束缚轨道上的伴星。GJ 758 B的H-L'色比几乎所有已知的L-T8矮星都要红。根据与COND演化模型的比较，GJ 758 B的$_{e}$ $\sim$为560 K $^{^{+150 K}_{-90K}}$，质量范围从$\sim$ 10- 20 M $_{J}$（如果它的年龄为1 Gyr）到$\sim$ 25- 40 M $_{J}$（如果它的年龄为8.7 Gyr）。GJ 758 B可能在一个高度偏心的轨道上，e $\sim$ 0.73 $^{^{+0.12}_{-0.21}}$，半长轴$\sim$ 44 AU $^{^{+32 AU}_{-14 AU}}$。虽然GJ 758 B有时会在系外行星直接成像的背景下讨论，但它的质量可能大于氘燃烧极限，它的形成可能类似于双星，而不是木星质量的行星。

英文摘要：

We present L' band (3.8 $μm$) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one -- possibly two-- faint comoving companions (GJ 758B and ``C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \textit{possible} detection of the object identified by Thalmann et al as ``GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 758B has a H-L' color redder than nearly all known L--T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has T$_{e}$ $\sim$ 560 K$^{^{+150 K}_{-90K}}$ and a mass ranging from $\sim$ 10--20 M$_{J}$ if it is $\sim$ 1 Gyr old to $\sim$ 25--40 M$_{J}$ if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e $\sim$ 0.73$^{^{+0.12}_{-0.21}}$, with a semimajor axis of $\sim$ 44 AU$^{^{+32 AU}_{-14 AU}}$. Though GJ 758B is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

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