arXiv 1301.28772013-01-14astro-ph.SR

Be星HD 110432周围Brγ和He I发射线中存在非对称开普勒盘的证据

Evidence of an asymmetrical Keplerian disk in the Brγ and He I emission lines around the Be star HD 110432

Philippe Stee, A. Meilland, Ph. Bendjoya, F. Millour, M. Smith, A. Spang, G. Duvert, K. -H. Hofmann, F. Massi

备注：: 9 pages
DOI：: 10.1051/0004-6361/201220302

摘要：

上下文HD 110432被归类为“γCas X射线类似物”，因为它具有类似的特殊X射线和光学特性，即硬热X射线可变发射和受广泛圆盘影响的光谱。Lopes de Oliveira等人（2007年）认为它可能是一颗Be星，里面有一颗正在吸积的白矮星，或者X射线可能来自恒星表面和它的盘之间的相互作用。目标。为了研究这颗Be星周围的盘，我们使用了VLTI/AMBER仪器，它结合了高光谱（R=12000）和高空间分辨率（θmin =4 mas）。方法.我们约束的几何形状和运动学的拱星盘从有史以来最高的空间分辨率在这颗星上实现。结果采用高斯圆盘模型，得到了Brγ线上的圆盘扩展为10.2 D \ast，He I线上的圆盘扩展为7.8 D \ast.圆盘显然遵循开普勒旋转。我们得到了一个倾角为55 \degree，和恒星是一个近临界转子与Vrot /Vc =1.00 $\pm$ 0.2。该倾斜度大于γCas的值（约42 \degree，Stee等人，2012年），并且与Smith和Balona（2006年）根据光学Fe II发射曲线推断的倾斜度应大于γCas值一致。在近红外连续谱中，HD 110432的圆盘比γCas的圆盘大3倍。我们没有直接的证据表明HD 110432周围有伴星，但似乎我们有一个清晰的特征，表明在HD 110432周围发现了盘的不均匀性。这种不对称的磁盘检测可以解释单臂振荡粘性磁盘框架内。另一个发现是，在近红外的磁盘大小是类似的其他Be星与不同的光谱类型，因此可能是独立的恒星参数，发现经典的Be星。

英文摘要：

Context. HD 110432 was classified as a "γCas X-ray analog" since it has similar peculiar X-ray and optical characteristics, i.e. a hard-thermal X-ray variable emission and an optical spectrum affected by an extensive disk. Lopes de Oliveira et al. (2007) suggest that it might be a Be star harboring an accreting white dwarf or that the X-rays may come from an interaction between the surface of the star and its disk. Aims. To investigate the disk around this Be star we used the VLTI/AMBER instrument, which combines high spectral (R=12000) and high spatial (θmin =4 mas) resolutions. Methods. We constrain the geometry and kinematics of its circumstellar disk from the highest spatial resolution ever achieved on this star. Results. We obtain a disk extension in the Brγ line of 10.2 D\ast and 7.8 D\ast in the He I line at 2.05 μm assuming a Gaussian disk model. The disk is clearly following a Keplerian rotation. We obtained an inclination angle of 55\degree, and the star is a nearly critical rotator with Vrot /Vc =1.00$\pm$0.2. This inclination is greater than the value found for γCas (about 42\degree, Stee et al. 2012), and is consistent with the inference from optical Fe II emission profiles by Smith & Balona (2006) that the inclination should be more than the γCas value. In the near-IR continuum, the disk of HD 110432 is 3 times larger than γCas's disk. We have no direct evidence of a companion around HD 110432, but it seems that we have a clear signature for disk inhomogeneities as detected for ζ Tau. This asymmetrical disk detection may be interpreted within the one-armed oscillation viscous disk framework. Another finding is that the disk size in the near-IR is similar to other Be stars with different spectral types and thus may be independent of the stellar parameters, as found for classical Be stars.

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