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arXiv 0810.2023astro-ph
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2006年蛇夫座RS爆发中演化激波的高分辨率X射线光谱学

High-resolution X-ray spectroscopy of the evolving shock in the 2006 outburst of RS Ophiuchi

J. -U. Ness, J. J. Drake, S. Starrfield, M. F. Bode, T. J. O'Brien, A. Evans, S. P. S. Eyres, L. A. Helton, J. P. Osborne, K. L. Page, C. Schneider, C. E. Woodward

摘要:

2006年蛇夫座经常性新星RS爆发的演化是通过钱德拉和XMM-牛顿的12个X射线光栅观测来跟踪的。我们提出了详细的光谱分析,使用两种独立的方法。从最好的数据集,在爆发后的第13.8天,我们重建的温度分布,并获得元素丰度。我们发现的证据,至少有两个不同的温度组件在第13.8天,并随着时间的推移温度降低。X射线通量呈幂律衰减,幂律指数在爆发后70天左右从-5/3变化到-8/3。这可以通过热分量和冷分量的不同衰变机制来解释。热成分的衰减和温度的降低与辐射冷却一致,而冷成分的衰减可以用喷出物的膨胀来解释。我们发现N和α元素的丰度过高,这可能代表提供吸积物质的次生物质的成分,也可能代表喷出物的成分。N的过量表示Hoc循环的物质。从文献中所采取的二次丰度的比较,我们得出结论,所观察到的氮的20-40%可能来自爆发。在RS-Oph系统中,α元素的过剩并不是光谱类型为次级的恒星的典型特征,白矮星的物质可能已经混入了喷出物中。然而,没有直接测量的α-元素的次级,和连续的吸积可能已经改变了可观察到的表面组成。

英文摘要:

The evolution of the 2006 outburst of the recurrent nova RS Ophiuchi was followed with 12 X-ray grating observations with Chandra and XMM-Newton. We present detailed spectral analyses using two independent approaches. From the best dataset, taken on day 13.8 after outburst, we reconstruct the temperature distribution and derive elemental abundances. We find evidence for at least two distinct temperature components on day 13.8 and a reduction of temperature with time. The X-ray flux decreases as a power-law, and the power-law index changes from -5/3 to -8/3 around day 70 after outburst. This can be explained by different decay mechanisms for the hot and cool components. The decay of the hot component and the decrease in temperature are consistent with radiative cooling, while the decay of the cool component can be explained by the expansion of the ejecta. We find overabundances of N and of alpha-elements, which could either represent the composition of the secondary that provides the accreted material or that of the ejecta. The N overabundance indicates CNO-cycled material. From comparisons to abundances for the secondary taken from the literature, we conclude that 20-40% of the observed nitrogen could originate from the outburst. The overabundance of the alpha-elements is not typical for stars of the spectral type of the secondary in the RS Oph system, and white dwarf material might have been mixed into the ejecta. However, no direct measurements of the alpha-elements in the secondary are available, and the continuous accretion may have changed the observable surface composition.

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