标题： 利用X-Shooter的LkCa 15光谱天文学：搜寻LkCa 15b的发射 显示英文标题

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

摘要： 行星形成是解释一些金牛座T型星盘中观测到的尘埃部分清除现象的一种解释。事实上，最近使用最先进的高角分辨率技术的研究已经开始在这类所谓的过渡盘中观测到行星伴星。本研究的目标是利用使用甚大望远镜上的X-Shooter光谱仪获得的过渡盘目标LkCa 15的光谱来探讨使用光谱偏振法检测金牛座T型星行星伴星的可能性。有人认为，一个吸积中的行星应该对诸如H$α$等吸积示踪剂的总发射有所贡献，因此可以通过光谱偏振法检测行星伴星，就像它被用来检测年轻恒星的伴星一样。最近，在LkCa 15盘中探测到了一个可能具有行星质量的伴星。因此，这是一个理想的目标用于这项试点研究。我们用光谱偏振法研究了波长范围从300纳米到2.2$μ$米之间的几个关键吸积线。虽然没有测量到任何发射线的光谱偏振信号，但该技术达到的精度被用来对行星对H$α$、Pa$γ$和Pa$β$线的流量贡献设置上限。 由此得到的通量上限制定了吸积率的上限，假设伴星质量在6 M$_{Jup}$到15 M$_{Jup}$之间，则可以估算出log($\dot{M}_{acc}$) = -8.9到-9.3（基于某些假设）。 显示英文摘要

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).