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arXiv 0804.2436astro-ph
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通过光度变化发现的PN的中心双星。I.我们所知道的和我们想知道的

Binary central stars of PN discovered through photometric variability. I. What we know and what we would like to find out

Orsola De Marco, Todd C. Hillwig, A. J. Smith

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39 pages, 4 figures. Accepted for publication in the Astronomical Journal
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摘要：

如果一个伴星与渐近巨星分支顶端的一个主星相互作用，那么轴对称行星状星云的形成就比较容易。为了确定双星对行星状星云形成和成形的影响，我们需要确定行星状星云双星的中心恒星比例和周期分布。根据对约100颗中心恒星的光度变化的测量，短周期双星的比例为10-15%，这些光度变化表明了辐射效应、椭球变化或食。这种调查技术被认为是对长周期的双星有偏见，这一事实被用来解释为什么这次调查发现的所有双星的周期都小于3天。在本文中，我们评估的知识，因为辐射效应发现的双星中心的状态。我们确定，对于平均参数，这种技术应该偏向于超过1-2周的周期，因此令人惊讶的是，没有发现周期超过3天的二进制文件。更令人困惑的是，12个受辐射的双星中有9个的周期小于一天，这一事实与后共同包络预测完全不一致。我们认为，无论是所有常见的信封模型往往高估后共同信封期间或这种二元调查可能遭受额外的，未量化的偏见。如果后一种假设是正确的，那么目前已知的短周期双星分数就受到了严重的质疑。我们还介绍了一个新的调查二进制相关的变异性，这将使我们能够更好地量化偏差，并确定一个独立的值为短周期的二进制分数。

英文摘要：

Shaping axi-symmetric planetary nebulae is easier if a companion interacts with a primary at the top of the asymptotic giant branch. To determine the impact of binarity on planetary nebula formation and shaping, we need to determine the central star of planetary nebula binary fraction and period distribution. The short-period binary fraction has been known to be 10-15% from a survey of ~100 central stars for photometric variability indicative of irradiation effects, ellipsoidal variability or eclipses. This survey technique is known to be biased against binaries with long periods and this fact is used to explain why the periods of all the binaries discovered by this survey are smaller than 3 days. In this paper we assess the status of knowledge of binary central stars discovered because of irradiation effects. We determine that, for average parameters, this technique should be biased against periods longer than 1-2 weeks, so it is surprising that no binaries were found with periods longer than 3 days. Even more puzzling is the fact that 9 out of 12 of the irradiated binaries, have periods smaller than one day, a fact that is starkly at odds with post-common envelope predictions. We suggest that either all common envelope models tend to overestimate post-common envelope periods or that this binary survey might have suffered from additional, unquantified biases. If the latter hypothesis is true, the currently-known short-period binary fraction is put in serious doubt. We also introduce a new survey for binary-related variability, which will enable us to better quantify biases and determine an independent value for the short period binary fraction.

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。

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