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arXiv 0908.3810astro-ph.HEastro-ph.GA
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新星喷出物作为碰撞壳

Novae Ejecta as Colliding Shells

Robert Williams, Elena Mason

摘要:

继我们最初的吸收线分析15新星光谱,我们提出了额外的证据,新星喷出物具有不同的起源两个不同的组成部分的存在。正如论文I中所论证的,其中一个成分是由爆发从白矮星外层喷射出的快速膨胀的气体。第二种成分是预先存在的外部,更缓慢地膨胀的环联星气体,代表从二级恒星或吸积盘喷出的物质。我们目前的测量的发射线的宽度,显示它们是显着窄于广泛的天鹅座P配置文件,立即在他们之前。在星云阶段,新星的发射轮廓是明显的矩形,即,强烈地暗示着从一个相对薄的,大致球形的壳中发射。因此,我们解释新星的光谱演化的喷出物的两个组成部分之间的碰撞,它转换成早期的吸收光谱的发射线光谱数周内的爆发。狭窄的发射宽度要求外环双星的气体比白矮星喷出物的质量大得多,从而减缓了后者在碰撞时的膨胀。在爆发时存在一个大型的环双星气体储层,这表明新星爆发有时可能是由气体坍塌到白矮星上引发的,就像矮新星一样,而不是通过内部拉格朗日点进行稳定的质量转移。

英文摘要:

Following on our initial absorption-line analysis of fifteen novae spectra we present additional evidence for the existence of two distinct components of novae ejecta having different origins. As argued in Paper I one component is the rapidly expanding gas ejected from the outer layers of the white dwarf by the outburst. The second component is pre-existing outer, more slowly expanding circumbinary gas that represents ejecta from the secondary star or accretion disk. We present measurements of the emission-line widths that show them to be significantly narrower than the broad P Cygni profiles that immediately precede them. The emission profiles of novae in the nebular phase are distinctly rectangular, i.e., strongly suggestive of emission from a relatively thin, roughly spherical shell. We thus interpret novae spectral evolution in terms of the collision between the two components of ejecta, which converts the early absorption spectrum to an emission-line spectrum within weeks of the outburst. The narrow emission widths require the outer circumbinary gas to be much more massive than the white dwarf ejecta, thereby slowing the latter's expansion upon collision. The presence of a large reservoir of circumbinary gas at the time of outburst is suggestive that novae outbursts may sometime be triggered by collapse of gas onto the white dwarf, as occurs for dwarf novae, rather than steady mass transfer through the inner Lagrangian point.

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