The Mass Dependence of Planet Formation: A Search for Extrasolar Planets Around A-F-type Stars

该项目将开始使用精确的恒星径向速度(RV)首次广泛搜索A-F型主序恒星周围的太阳系外行星。这些恒星在很大程度上被目前所有的调查所忽视。因此，我们只有关于恒星周围的太阳系外行星的知识，覆盖了恒星F8-K1的狭窄光谱范围(因此也就是质量)。因此，我们对行星的形成如何随恒星的最基本参数--它的质量--而变化知之甚少。有几个项目正在寻找晚型M型矮星周围的行星，但还没有系统地寻找早期类型恒星周围的行星。通过发现质量较大的早期恒星周围的行星，我们可以探索行星的形成过程是如何依赖于主星的质量的，这对行星形成理论是至关重要的。该计划将在一类特殊的A星周围寻找太阳系外行星，A星是一种化学上特殊的AP星。这些天体更适合于在正常的A星上进行RV搜索，因为它们的自转速度较慢，而且它们具有特殊的丰度，这转化为高密度的光谱吸收线。初步测量表明，这些恒星的径向速度精度可能达到7m/S左右。这样的测量将能够探测到围绕这些恒星的轨道上的太阳系外巨行星。我们建议在一个相当大的样本(至少100颗恒星)的A型恒星周围寻找太阳系外行星，从而探索行星形成与恒星质量的关系。

This project will start the first extensive search for extrasolar planets around A-F type main sequence stars using precise stellar radial velocities (RV). These stars have largely been ignored by all current survey. As a result we only have knowledge about extrasolar planets around stars covering the narrow spectral (and thus mass) range of stars F8-K1. Consequently, we have little understanding of how planet formation varies with the most fundamental parameter of a star - its mass. Several programs are searching for planets around late type M-dwarfs, but no systematic search has been made for planets around early- type stars. By finding planets around the more massive earlier type stars we can probe how the process of planet formation depends on the mass of the host star which is of fundamental importantance for planet formation theories. This program will search for extrasolar planets around a special class of A stars, the chemically peculiar Ap stars. These objects are more suitable for RV searches over normal A-stars because they rotate less rapidly and they have peculiar abundances which translates into a high density of spectral absorption lines. Preliminary measurements indicate that a radial velocity precision of about 7 m/s is possible for these stars. Such measurements will be able to detect extrasolar giant planets in orbit around these stars. We propose to search for extrasolar planets around a significantly large sample (at least 100 stars) of A-type stars and thus probe the dependence of planet formation on stellar mass.