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arXiv 1504.04824astro-ph.SR
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用X-Shooter对LkCa 15进行光谱天体测量：寻找LkCa 15 b的发射

Spectro-astrometry of LkCa 15 with X-Shooter: Searching for emission from LkCa 15b

E. T. Whelan, N. Huelamo, J. M. Alcala, J. Lillo-Box, H. Bouy, D. Barrado, J. Bouvier, B. Merin

备注：
Accepted by Astronomy & Astrophysics
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摘要：

行星形成是在一些金牛座T型恒星的盘中观察到的部分尘埃清除的一种解释。事实上，使用最先进的高角分辨率技术的研究最近已经开始观察这些所谓的过渡盘中的行星伴星。这项工作的目标是利用超大望远镜上的X-射手获得的过渡盘物体LkCa 15的光谱，研究使用光谱天体测量法探测金牛T星的行星伴星的可能性。有人认为，一个吸积行星应有助于吸积示踪剂，如H $α$的总排放量，因此行星的同伴可以检测光谱天体测量的方式相同，它已被用来检测恒星同伴年轻的恒星。最近在LkCa 15的圆盘中发现了一个可能的行星质量伴星。因此，它是本试点研究的理想目标。我们用光谱天体测量法研究了300 nm到2.2 $μ$ m波长范围内的几条关键吸积线。虽然没有测量到任何发射线的光谱天文测量信号，但该技术所达到的精度被用来确定行星对H $α$、Pa $γ$和Pa $β$线通量的贡献的上限。导出的流量上限允许质量吸积率的上限，log（$\dot{M}_{acc}$）= -8.9到-9.3之间的伴星质量6 M $_{Jup}$和15 M $_{Jup}$，分别进行估计（有一些假设）。

英文摘要：

Planet formation is one explanation for the partial clearing of dust observed in the disks of some T Tauri stars. Indeed studies using state-of-the-art high angular resolution techniques have very recently begun to observe planetary companions in these so-called transitional disks. The goal of this work is to use spectra of the transitional disk object LkCa 15 obtained with X-Shooter on the Very Large Telescope to investigate the possibility of using spectro-astrometry to detect planetary companions to T Tauri stars. It is argued that an accreting planet should contribute to the total emission of accretion tracers such as H$α$ and therefore planetary companions could be detected with spectro-astrometry in the same way as it has been used to detect stellar companions to young stars. A probable planetary-mass companion was recently detected in the disk of LkCa 15. Therefore, it is an ideal target for this pilot study. We studied several key accretion lines in the wavelength range 300 nm to 2.2 $μ$m with spectro-astrometry. While no spectro-astrometric signal is measured for any emission lines the accuracy achieved in the technique is used to place an upper limit on the contribution of the planet to the flux of the H$α$, Pa$γ$, and Pa$β$ lines. The derived upper limits on the flux allows an upper limit of the mass accretion rate, log($\dot{M}_{acc}$) = -8.9 to -9.3 for the mass of the companion between 6 M$_{Jup}$ and 15 M$_{Jup}$, respectively, to be estimated (with some assumptions).

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