Investigating the origin and spectroscopic variability of the near-infrared H I lines in the Herbig star VV Ser
Investigating the origin and spectroscopic variability of the near-infrared H I lines in the Herbig star VV Ser
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DOI：
10.1093/mnras/stv2664
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发表时间：
2015-11
影响因子：
4.8
通讯作者：
R. L'opez;R. Kurosawa;A. C. O. Garatti;A. Kreplin;G. Weigelt;L. Tambovtseva;V. Grinin;T. Ray
中科院分区：
文献类型：
--
作者：
R. L'opez;R. Kurosawa;A. C. O. Garatti;A. Kreplin;G. Weigelt;L. Tambovtseva;V. Grinin;T. Ray
年轻恒星中近红外(NIR)HI发射线的来源尚不清楚。为了探索它，我们给出了在赫比星VSer中观测到的Pa{\Delta}，Pa{\beta}和Br{\Gamma}线的多历元LBT-Lucifer光谱观测，以及VLTI-Amber BR{\Gamma}中分辨率的光谱干涉观测。我们的光谱观测显示，在所有HI谱线中，谱线轮廓都是可变性的。在谱线轮廓的红移部分观察到最强的变异性。BR{\伽马}光谱干涉观测表明，BR{\伽马}线发射区小于连续谱发射区。为了解释我们的结果，我们使用了三种不同流动形态的辐射传输模型：磁层吸积、磁离心力驱动的盘风和示意性双极外流。我们的模型表明，VVSer中的HI线发射是由扩展风的贡献主导的，可能是双极外流。虽然产生这种外流的确切物理过程尚不清楚，但该模型能够再现HI线的平均单峰线轮廓。此外，在考虑风的情况下，观测到的能见度、差分和闭合相位是最好的再现。然而，复杂的谱线轮廓和可变性可以用磁层和/或风对谱线发射的相对贡献的变化来解释。这可能表明近红外HI线是在一个复杂的内盘区域形成的，在那里流入和流出成分可能共存。此外，这些机制中的每一种对这条线的贡献都具有时变性，表明这是一种非稳定的吸积/喷出流。
The origin of the near-infrared (NIR) HI emission lines in young stellar objects are not yet understood. To probe it, we present multi-epoch LBT-LUCIFER spectroscopic observations of the Pa{\delta}, Pa{\beta}, and Br{\gamma} lines observed in the Herbig star VVSer, along with VLTI-AMBER Br{\gamma} spectro-interferometric observations at medium resolution. Our spectroscopic observations show line profile variability in all the HI lines. The strongest variability is observed in the redshifted part of the line profiles. The Br{\gamma} spectro-interferometric observations indicate that the Br{\gamma} line emitting region is smaller than the continuum emitting region. To interpret our results, we employed radiative transfer models with three different flow configurations: magnetospheric accretion, a magneto-centrifugally driven disc wind, and a schematic bipolar outflow. Our models suggest that the HI line emission in VVSer is dominated by the contribution of an extended wind, perhaps a bipolar outflow. Although the exact physical process for producing such outflow is not known, this model is capable of reproducing the averaged single-peaked line profiles of the HI lines. Additionally, the observed visibilities, differential and closure phases are best reproduced when a wind is considered. Nevertheless, the complex line profiles and variability could be explained by changes in the relative contribution of the magnetosphere and/or winds to the line emission. This might indicate that the NIR HI lines are formed in a complex inner disc region where inflow and outflow components might coexist. Furthermore, the contribution of each of these mechanisms to the line appears time variable, suggesting a non-steady accretion/ejection flow.