arXiv 0709.45122007-09-28astro-ph

2006年RS Oph大爆发的X射线能谱研究

X-ray Spectroscopy of the 2006 Outburst of RS Oph

Thomas Nelson, Marina Orio, Joseph P. Cassinelli, Martin Still, Elia Leibowitz, Paola Mucciarelli

备注：: Accepted for publication in the Astrophysical Journal; 39 pages, 4 tables, 14 figures
DOI：: 10.1086/524054

摘要：

我们提出的X射线光栅光谱的经常性新星RS蛇夫座在其2006年爆发，获得的XMM-牛顿和钱德拉天文台。光学极大值后两周，X射线光谱变硬，主要由类氢离子和类氦离子的发射线组成。X射线的亮度在0.33-10 keV范围内为2.4 x 10^36 erg s^-1。光谱表明，碰撞占主导地位的等离子体具有广泛的温度范围。所有谱线都发生了蓝移，且随着电离态的降低和波长的延长，速度位移增大。两周后，光谱仍然以发射线为主，尽管存在的线比率表明冷却。在这次观测中，发生了一次软X射线耀斑，在光谱的软端出现了一个新的高速发射线系统。在第三个月的主要组成部分是超软连续与广泛的吸收功能的热白矮星大气。初步的模型拟合表明，白矮星的温度略高于800，000 K。X射线的亮度在0.2-1 keV范围内至少达到9 x 10^37 erg s^-1，而星云的固有吸收比第一次观测时减少了五倍。光谱拟合表明这是一颗质量至少为1.2 M_ \odot的大质量白矮星。因此，RS Oph可能是一个重要的Ia型超新星祖先。我们表明，数据是一致的质量损失结束前54天的爆发后，和核燃烧结束69天左右。第10周后，X射线光度迅速衰减。光学极大值后5、7、8个月的X射线光度下降了两个数量级以上。这些光谱似乎与吸积盘的辐射不一致。

英文摘要：

We present the X-ray grating spectra of the recurrent nova RS Ophiuchi during its 2006 outburst, obtained with the XMM-Newton and Chandra observatories. Two weeks after optical maximum, the X-ray spectrum was hard and dominated by emission lines of H-like and He-like ions. The X-ray luminosity was 2.4 x 10^36 erg s^-1 in the 0.33-10 keV range. The spectra indicate a collisionally dominated plasma with a broad range of temperatures. All the lines are blue-shifted, with the velocity shift increasing with lower ionization state and longer wavelength. Two weeks later, the spectrum was still dominated by emission lines, although the line ratios present indicate cooling. During this observation, a soft X-ray flare occurred in which a new system of higher velocity emission lines appeared in the soft end of the spectrum. The dominant component during the third month was the supersoft continuum with the broad absorption features of a hot white dwarf atmosphere. A preliminary model fit indicates a white dwarf temperature slightly exceeding 800,000 K. The X-ray luminosity reached at least 9 x 10^37 erg s^-1 in the 0.2-1 keV range, while the intrinsic nebular absorption decreased by a factor of five since the first observation. The spectral fits indicate a massive white dwarf, with a mass of at least 1.2 M_\odot. Therefore, RS Oph may be an important type Ia supernova progenitor. We show that the data are consistent with mass loss ending before day 54 after the outburst, and nuclear burning ending around day 69. A rapid decay in X-ray luminosity followed after week 10. The X-ray luminosity 5, 7 and 8 months after optical maximum dropped by more than two orders of magnitude. The spectra do not appear to consistent with emission from an accretion disk.

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