将水平分支恒星周围的行星与已知的系外行星联系起来
Connecting planets around horizontal branch stars with known exoplanets
摘要：
我们研究了主序（MS）恒星周围系外行星的分布，并将我们的结果应用于极端水平分支（EHB; sdO; sdB;热次矮星）恒星形成的二元模型。通过双星模型，我们指的是恒星和亚恒星的同伴，提高质量损失率，其中亚恒星的同伴代表大质量行星和褐矮星。我们的结论是sdB（EHB）恒星是行星搜索的主要目标。我们得出这一结论是因为我们注意到，行星围绕恒星的双峰分布相对于参数M_p*a^2在质量范围为1 Mo < M < 1.5Mo的恒星中最为显著; 'a'是轨道间距，'M'是恒星质量，'M_p'是行星质量。这也是EHB恒星的祖先的质量范围，这些恒星是通过它们的祖先与行星的相互作用形成的（假设EHB的形成机制是双星模型）。在EHB星形成的双星模型中，与双星伴星或亚恒星物体（行星或棕矮星）的相互作用，导致其前身在红巨星分支（RGB）阶段失去了大部分的包层质量。因此，后代HB星是热的，即，一颗EHB（sdB）星。双峰分布表明，即使形成EHB恒星的近距离行星没有在其RGB共同包层演化中幸存下来，也可能有一颗或多颗行星在>1AU的位置幸存下来。此外，如果一颗或更多的行星在大于1AU的位置被观测到，那么有可能是一颗更近的大质量行星在共同包层阶段幸存下来，并且它以数小时到数天的轨道周期绕着EHB运行。
英文摘要：
We study the distribution of exoplanets around main sequence (MS) stars and apply our results to the binary model for the formation of extreme horizontal branch (EHB; sdO; sdB; hot subdwarfs) stars. By Binary model we refer both to stellar and substellar companions that enhance the mass loss rate, where substellar companions stand for both massive planets and brown dwarfs. We conclude that sdB (EHB) stars are prime targets for planet searches. We reach this conclusion by noticing that the bimodal distribution of planets around stars with respect to the parameter M_p*a^2, is most prominent for stars in the mass range 1Mo < M < 1.5Mo; 'a' is the orbital separation, 'M' is the stellar mass and 'M_p' the planet mass. This is also the mass range of the progenitors of EHB stars that are formed through the interaction of their progenitors with planets (assuming the EHB formation mechanism is the binary model). In the binary model for the formation of EHB stars interaction with a binary companion or a substellar object (a planet or a brown dwarf), causes the progenitor to lose most of its envelope mass during its red giant branch (RGB) phase. As a result of that the descendant HB star is hot, i.e., an EHB (sdB) star. The bimodal distribution suggests that even if the close-in planet that formed the EHB star did not survive its RGB common envelope evolution, one planet or more might survive at a>1AU. Also, if a planet or more are observed at a>1AU, it is possible that a closer massive planet did survive the common envelope phase, and it is orbiting the EHB with an orbital period of hours to days.
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