用CO带头和Br γ辐射研究Herbig Ae/Be星的内盘
Investigating the inner discs of Herbig Ae/Be stars with CO bandhead and Br Gamma emission
摘要：
赫比格Ae/Be星位于低质量和高质量年轻恒星之间的质量范围内，因此提供了一个独特的机会来观察可能发生在这个边界上的形成过程中的任何变化。本文给出了从91个目标中选取的6颗Herbig Ae/Be星的中等分辨率VLT/X-Shooter光谱，以及根据光谱中CO第一泛音带头发射的存在选取的5颗Herbig Ae/Be星的高分辨率VLT/CRIRES光谱。X-Shooter巡天显示，CO第一泛音发射的探测率很低（7%），主要由光谱类型为B的物体组成。CO v=2-0和Br γ发射线的强度之间存在正相关关系，尽管它们的内在线宽表明它们是独立的运动学起源。高分辨率的CRIRES光谱建模，并很好地拟合的假设下，发射源自小尺度开普勒光盘，内部的尘埃升华半径，但外的中心恒星的共同旋转半径。此外，我们的研究结果是非常好的协议的一个对象，空间分辨近红外干涉研究也进行了。这些结果表明，Herbig Ae/Be恒星的问题是在获得质量通过光盘吸积的过程中，高光谱分辨率光谱的建模能够提供一个可靠的探测到恒星吸积过程中的年轻恒星的中间到高质量。
英文摘要：
Herbig Ae/Be stars lie in the mass range between low and high mass young stars, and therefore offer a unique opportunity to observe any changes in the formation processes that may occur across this boundary. This paper presents medium resolution VLT/X-Shooter spectra of six Herbig Ae/Be stars, drawn from a sample of 91 targets, and high resolution VLT/CRIRES spectra of five Herbig Ae/Be stars, chosen based on the presence of CO first overtone bandhead emission in their spectra. The X-Shooter survey reveals a low detection rate of CO first overtone emission (7 per cent), consisting of objects mainly of spectral type B. A positive correlation is found between the strength of the CO v=2-0 and Br γ emission lines, despite their intrinsic linewidths suggesting a separate kinematic origin. The high resolution CRIRES spectra are modelled, and are well fitted under the assumption that the emission originates from small scale Keplerian discs, interior to the dust sublimation radius, but outside the co-rotation radius of the central stars. In addition, our findings are in very good agreement for the one object where spatially resolved near-infrared interferometric studies have also been performed. These results suggest that the Herbig Ae/Be stars in question are in the process of gaining mass via disc accretion, and that modelling of high spectral resolution spectra is able to provide a reliable probe into the process of stellar accretion in young stars of intermediate to high masses.
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