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arXiv 1801.07951astro-ph.SRastro-ph.EP
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碎片盘中冷热气体的共存

The co-existence of hot and cold gas in debris discs

I. Rebollido, C. Eiroa, B. Montesinos, J. Maldonado, E. Villaver, O. Absil, A. Bayo, H. Canovas, A. Carmona, Ch. Chen, S. Ertel, A. Garufi, Th. Henning, D. P. I… 展开作者

I. Rebollido, C. Eiroa, B. Montesinos, J. Maldonado, E. Villaver, O. Absil, A. Bayo, H. Canovas, A. Carmona, Ch. Chen, S. Ertel, A. Garufi, Th. Henning, D. P. Iglesias, R. Laundhart, R. Lisseau, G. Meeus, A. Móor, A. Mora, J. Olofsson, G. Rauw, P. Riviere-Marichalar

摘要:

碎片盘经常被描述为贫气盘,因为气体与尘埃的比率预计要比原始的原行星盘低得多。然而,最近的观测证实,在年轻的主序星周围的星周碎片盘中存在着不可忽略的冷气体,这种冷气体被认为与微行星和类彗星天体的脱气有关。该文件的目的是调查在周围的恒星轴承冷气碎片盘的热气的存在。除了$β$ Pic和北落师门外,我们已经从不同的天文台获得了所有目前已知的含冷气的碎片盘系统的高分辨率光谱,我们分析了Ca II H & K和Na I D线,寻找通常归因于类彗星活动的CS起源的非光球层反射。狭窄的,稳定的钙II和/或钠I吸收功能已被检测到叠加到光球线在10个观察到的15个冷气体轴承碎片disption.Features被发现在恒星的径向速度,或略有蓝移或红移,和/或在当地的星际介质(ISM)的速度。有些恒星也呈现出向红色波长延伸的瞬变事件或反射。这是第一次在15颗观测到的恒星中的7颗中检测到这种Ca II特征。在这些恒星中的一些,结果表明,稳定和可变的反射来自相对较热的气体位于CS接近环境。这种热气体被检测到在至少~ 80%,边缘上的冷气轴承碎片光盘,而在只有~10%的光盘看到接近face-on. We解释这是一个几何效应,并建议,未检测到热气体的反射是由于光盘的倾斜,而不是没有热气体成分。

英文摘要:

Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial,protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars.This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. The aim of the paper is to investigate the presence of hot gas in the surroundings of stars bearing cold-gas debris discs. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of $β$ Pic and Fomalhaut, have been obtained from different observatories.We have analysed the Ca II H & K and the Na I D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity. Narrow, stable Ca II and/or Na I absorption features have been detected superimposed to the photospheric lines in 10 out of the 15 observed cold-gas-bearing debris disc.Features are found at the radial velocity of the stars, or slightly blue- or red-shifted, and/or at the velocity of the local interstellar medium (ISM). Some stars also present transient variable events or absorptions extended towards red wavelengths. These are the first detections of such Ca II features in 7 out of the 15 observed stars. In some of these stars, results suggest that the stable and variable absorptions arise from relatively hot gas located in the CS close-in environment. This hot gas is detected in at least ~80%, of edge-on cold-gas-bearing debris discs, while in only ~10% of the discs seen close to face-on. We interpret this as a geometrical effect, and suggest that the non-detection of hot gas absorptions is due to the disc inclination rather than to the absence of the hot-gas component.

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