造父变星的秘密XUV生命：北极星和β-Dor的FUV/X射线观测
The Secret XUV Lives of Cepheids: FUV/X-ray Observations of Polaris and beta Dor
摘要：
我们报告了最近在两个明亮的，附近的经典造父变星中发现的强FUV辐射，这是从FUSE档案观测和我们自己批准的观测结果之一的分析中发现的。Polaris和beta Dor是目前仅有的两个用FUSE观测到的造父变星，beta Dor是唯一一个有多个光谱的造父变星。这两颗造父变星都有很强的C III（977 A，1176 A）和O VI（1032 A，1038 A）辐射，显示出50，000 - 500，000 K的等离子体，远高于恒星的光球温度。更值得注意的是，β Dor显示FUV发射强度的变化，这似乎与其9.84-d脉动周期相关。这种现象以前从未在造父变星中观察到过。FUV的研究与我们最近的钱德拉/XMM X射线观测北极星和β Dor，其中X射线检测发现这两颗恒星（以及原型经典造父变星，δ Cep）。进一步的X射线观测已经被提出来明确地确定观测到的来自目标的高能发射的起源和性质，可能是由暖风、冲击或脉动诱导的磁活动引起的。本研究的初步结果进行了讨论。
英文摘要：
We report on the surprising recent discovery of strong FUV emissions in two bright, nearby Classical Cepheids from analyses of FUSE archival observations and one of our own approved observations just prior to the failure of the satellite. Polaris and beta Dor are currently the only two Cepheids to have been observed with FUSE, and beta Dor is the only one to have multiple spectra. Both Cepheids show strong C III (977A, 1176A) and O VI (1032A, 1038A) emissions, indicative of 50,000-500,000 K plasma, well above the photospheric temperatures of the stars. More remarkably, beta Dor displays variability in the FUV emission strengths which appears to be correlated to its 9.84-d pulsation period. This phenomenon has never before been observed in Cepheids. The FUV studies are presented along with our recent Chandra/XMM X-ray observations of Polaris and beta Dor, in which X-ray detections were found for both stars (as well as for the prototype Classical Cepheid, delta Cep). Further X-ray observations have been proposed to unambiguously determine the origin and nature of the observed high energy emissions from the targets, possibly arising from warm winds, shocks, or pulsationally induced magnetic activity. The initial results of this study are discussed.
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