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arXiv 1109.2616astro-ph.HE
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已发布的X射线光变曲线告诉我们有关年轻超新星膨胀的哪些信息？

What are Published X-ray lightcurves telling us about Young Supernova Expansion?

Vikram V. Dwarkadas, Julieta Gruszko

备注：
12 pages, 3 color Figures. Accepted to MNRAS
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摘要：

大质量恒星以恒星风和爆发的形式失去质量。这些物质聚集在恒星周围。当恒星爆炸成为超新星（SN）时，产生的冲击波在这种星周介质中膨胀。由相互作用产生的X射线发射取决于该介质的密度以及其他参数，因此X射线光度的变化可以用于研究介质的密度结构的变化。在本文中，我们探讨了所有已知的SNe的X射线发射和光变曲线，以研究它们正在膨胀的介质的性质。特别是，我们希望调查是否年轻的SNe扩展到一个稳定的风介质，最常见的假设在文献中。我们发现，在文献中普遍使用的理论参数的背景下，许多年轻的SNe，特别是那些类型IIn，这是最明亮的X射线光度类，似乎并没有扩大到稳定的风。一些IIn似乎有非常陡峭的X射线光度下降，表明密度下降比r $^{-2}$更陡峭。然而，其他的IIns在几个月到几年的时间里表现出恒定的或甚至增加的X射线光度。许多其他SNe似乎并没有出现与稳定风中的扩张一致的下降。具有较低X射线光度的SNe似乎与稳定的风膨胀更一致，尽管这些数字还不足以做出可靠的统计评论。这些数字确实表明，在假设稳定的风膨胀之前，必须先研究星周介质的膨胀和密度结构。除非能证明有稳定的风，否则用这种假设推导出的质量损失率可能需要修正。

英文摘要：

Massive stars lose mass in the form of stellar winds and outbursts. This material accumulates around the star. When the star explodes as a supernova (SN) the resulting shock wave expands within this circumstellar medium. The X-ray emission resulting from the interaction depends, among other parameters, on the density of this medium, and therefore the variation in the X-ray luminosity can be used to study the variation in the density structure of the medium. In this paper we explore the X-ray emission and lightcurves of all known SNe, in order to study the nature of the medium into which they are expanding. In particular we wish to investigate whether young SNe are expanding into a steady wind medium, as is most often assumed in the literature. We find that in the context of the theoretical arguments that have been generally used in the literature, many young SNe, and especially those of Type IIn, which are the brightest X-ray luminosity class, do not appear to be expanding into steady winds. Some IIns appear to have very steep X-ray luminosity declines, indicating density declines much steeper than r$^{-2}$. However, other IIns show a constant or even increasing X-ray luminosity over periods of months to years. Many other SNe do not appear to have declines consistent with expansion in a steady wind. SNe with lower X-ray luminosities appear to be more consistent with steady wind expansion, although the numbers are not large enough to make firm statistical comments. The numbers do indicate that the expansion and density structure of the circumstellar medium must be investigated before assumptions can be made of steady wind expansion. Unless a steady wind can be shown, mass-loss rates deduced using this assumption may need to be revised.

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