天鹅座EM中的白矮星：面纱之外
The White Dwarf in EM Cygni: Beyond The Veil
摘要：
我们提出了一个光谱分析的FUSE光谱的EM天鹅座，Z凸轮DN系统。在静止期获得的FUSE光谱由4个单独的曝光（轨道）组成：在轨道相位φ ~ 0.65和φ ~ 0.90的两个曝光具有较低的通量;在轨道相位φ =0.15和0.45的两个曝光具有相对较高的通量。作为轨道相位函数的通量水平的变化与流物质（从热点区域到较小半径的盘上方和下方流动）部分掩盖了白矮星是一致的。我们进行频谱分析的FUSE数据，获得在相位0.45（当通量是最大的，使用代码TLUSTY和SYNSPEC。利用单个白矮星光谱分量，我们得到了一个温度为40，000 K，自转速度为100 km/s的白矮星。这颗白矮星，或者可以想象的是，溢出圆盘边缘的物质，显示出太阳系外丰富的硅、硫和可能的氮。利用白矮星+盘的复合模型，我们得到了白矮星的温度甚至可以高达50,000 K，贡献了90%以上的FUV通量，而贡献小于10%的盘必须具有1.E-10 Msun/yr的质量吸积率。然而，在这两种情况下，我们得到的白矮星的温度比以前估计的要高得多。
英文摘要：
We present a spectral analysis of the FUSE spectra of EM Cygni, a Z Cam DN system. The FUSE spectrum, obtained in quiescence, consists of 4 individual exposures (orbits): two exposures, at orbital phases phi ~ 0.65 and phi ~ 0.90, have a lower flux; and two exposures, at orbital phases phi =0.15 and 0.45, have a relatively higher flux. The change of flux level as a function of the orbital phase is consistent with the stream material (flowing over and below the disk from the hot spot region to smaller radii) partially masking the white dwarf. We carry out a spectral analysis of the FUSE data, obtained at phase 0.45 (when the flux is maximual, using the codes TLUSTY and SYNSPEC. Using a single white dwarf spectral component, we obtain a white dwarf temperature of 40,000K, rotating at 100km/s. The white dwarf, or conceivably, the material overflowing the disk rim, shows suprasolar abundances of silicon, sulphur and possibly nitrogen. Using a white dwarf+disk composite model, we obtain that the white dwarf temperature could be even as high as 50,000K, contributing more than 90% of the FUV flux, and the disk contributing less than 10% must have a mass accretion rate reaching 1.E-10 Msun/yr.In both cases, however, we obtain that the white dwarf temperature is much higher than previously estimated.
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