论文标题
中等分辨率$ k $ -band companion companion VHS 1256 b
Moderate-Resolution $K$-Band Spectroscopy of the Substellar Companion VHS 1256 b
论文作者
论文摘要
我们提出中等分辨率（$ r \ sim4000 $）$ k $ band spectra of planetary-mass companion vhs 1256 b。数据是在W.M.上使用Osiris积分谱仪进行的。凯克天文台。光谱揭示了来自H $ _ {2} $ O and Co的分子线的分子线。将光谱与适合年轻的替代物体的自定义$ phoenix $氛围模型进行了比较。我们使用马尔可夫链蒙特卡洛前向建模方法拟合数据。 Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of 1240 K, with a range of 1200--1300 K, a surface gravity of $\log{g}=$ 3.25, with a range of 3.25--3.75 and a cloud parameter of $\log P_{cloud}=$ 6, with a range of 6.0--6.6.这些值与以前的研究一致，无论新的，更大的系统距离与GAIA EDR3的较大距离（22.2 $^{+1.1} _ { - 1.2} $ PC）。对于VHS 1256B，我们得出0.590 $ _ { - 0.354}^{+0.280} $的C/O比率。我们的Osiris数据和文献中的光谱都是最好的建模，当对云中使用更大的3 $ $ m晶粒尺寸比用于热对象所用的云大小，这与L/T过渡区域中的其他来源一致。 VHS 1256 B提供了一个机会，可以在建模过程中查找系统学，这可能导致高对比度方案中c/o比率等属性的不正确派生。
We present moderate-resolution ($R\sim4000$) $K$ band spectra of the planetary-mass companion VHS 1256 b. The data were taken with the OSIRIS integral field spectrograph at the W.M. Keck Observatory. The spectra reveal resolved molecular lines from H$_{2}$O and CO. The spectra are compared to custom $PHOENIX$ atmosphere model grids appropriate for young, substellar objects. We fit the data using a Markov Chain Monte Carlo forward modeling method. Using a combination of our moderate-resolution spectrum and low-resolution, broadband data from the literature, we derive an effective temperature of 1240 K, with a range of 1200--1300 K, a surface gravity of $\log{g}=$ 3.25, with a range of 3.25--3.75 and a cloud parameter of $\log P_{cloud}=$ 6, with a range of 6.0--6.6. These values are consistent with previous studies, regardless of the new, larger system distance from GAIA EDR3 (22.2$^{+1.1}_{-1.2}$ pc). We derive a C/O ratio of 0.590$_{-0.354}^{+0.280}$ for VHS 1256b. Both our OSIRIS data and spectra from the literature are best modeled when using a larger 3 $μ$m grain size for the clouds than used for hotter objects, consistent with other sources in the L/T transition region. VHS 1256 b offers an opportunity to look for systematics in the modeling process that may lead to the incorrect derivation of properties like C/O ratio in the high contrast regime.
