SU Lyn：用UV和硬X射线数据诊断边界层
SU Lyn: diagnosing the boundary layer with UV and hard X-ray data
摘要：
共生星的共生现象完全由吸积提供动力，其平均吸积率通常高于激变变星，这为诊断吸积盘周围的白矮星边界层提供了重要机会。在这里，我们调查SU Lyncis，一个最近发现的例子，一个纯粹的吸积动力共生星，使用第一个可靠的X射线光谱，获得与NuSTAR，紫外测光与雨燕。SU Lyn具有硬的、热的X射线发射，该发射受到可变局部吸收体的强烈影响-这对UV发射几乎没有影响。它的X射线光谱使用$k$ T $\approx$ 21 keV的等离子体冷却进行了很好的描述，其中3至30 keV的光度约为4.9 $\times$ 10 $^{32}$尔格s $^{-1}$。光谱也与振幅为1.0的反射的存在一致，尽管在这种情况下，最佳拟合的等离子体温度低20-25%。SU Lyn的紫外线与X射线光度比在2015年和2016年之间发生了显着变化。我们将此解释为吸积率下降近90%的结果。尽管圆盘的UV光度呈线性响应，但来自边界层的光学薄（硬X射线）发射的光度大致保持不变，因为边界层从部分光学厚变为几乎完全光学薄。根据这种解释，我们将白矮星的质量下限定为0.7 M $_{\odot}$（如果忽略反射，则为0.8 M $_{\odot}$）。
英文摘要：
Symbiotic stars in which the symbiotic phenomenon is powered solely by accretion, often at an average rate that is higher than in cataclysmic variable stars, provide an important opportunity to diagnose boundary layers around disk-accreting white dwarfs. Here we investigate SU Lyncis, a recently discovered example of a purely accretion-powered symbiotic star, using the first reliable X-ray spectroscopy, obtained with NuSTAR, and UV photometry obtained with Swift. SU Lyn has hard, thermal, X-ray emission that is strongly affected by a variable local absorber - that has little impact on the UV emission. Its X-ray spectrum is described well using a plasma cooling from $k$T $\approx$ 21 keV, with a 3 to 30 keV luminosity of approximately 4.9$\times$10$^{32}$ ergs s$^{-1}$. The spectrum is also consistent with the presence of reflection with an amplitude of 1.0, although in that case, the best-fit plasma temperature is 20-25% lower. The UV to X-ray luminosity ratio of SU Lyn changed significantly between 2015 and 2016. We interpret this as a consequence of a drop by almost 90% in the accretion rate. Whereas the UV luminosity of the disk responded linearly, the luminosity of the optically thin (hard X-ray) emission from the boundary layer remained roughly constant because the boundary layer changed from partially optically thick to almost completely optically thin. Under this interpretation, we place a lower limit on the white dwarf mass of 0.7 M$_{\odot}$ (0.8 M$_{\odot}$ if we neglect reflection).
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
