Multi-object spectroscopy of stars in the CoRoT fields II: The stellar population of the CoRoT fields IRa01, LRa01, LRa02, and LRa06
Multi-object spectroscopy of stars in the CoRoT fields II: The stellar population of the CoRoT fields IRa01, LRa01, LRa02, and LRa06
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DOI：
10.1051/0004-6361/201219121
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
E. Guenther;Davide Gandolfi;D. Sebastian;M. Deleuil;C. Moutou;F. Cusano
中科院分区：
文献类型：
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作者：
E. Guenther;Davide Gandolfi;D. Sebastian;M. Deleuil;C. Moutou;F. Cusano
CoRoT现在发现了20多颗系外行星，其中有这么多是围绕F星运行的，而K星或M星却如此之少，这经常被认为是奇怪的。尽管凌日搜索计划大多对短周期行星敏感，但它们是验证这些结果的理想选择。为了确定行星的频率作为恒星质量的函数，我们还必须对观测到的恒星样本进行表征。我们通过测定11466颗恒星的光谱类型，研究了CoRoT场IRa01、LRa01(=LRa06)和LRa02的恒星含量。我们使用了多目标光谱仪AAOmega获得的光谱，并利用已知参数的模板光谱得出了光谱类型。我们发现CoRoT观测到的恒星中有34.8+/-0.7%是F矮星，15.1+/-0.5%是G-矮星，5.0+/-0.3%是K-矮星。我们的结论是，K星和M星明显缺乏系外行星的原因是这些恒星在观测样本中的数量相对较少。我们还表明，表面上围绕F-星运行的大量行星也同样可以用这些区域中大量的此类恒星来解释。我们的研究还表明，CoRoT观测到的恒星样本与随机选择的恒星样本之间的差异相对较小，CoRoT的产额具体是在2100+/-700颗恒星中探测到一颗热木星。我们的结论是，凌日搜索程序可以用来研究行星频率和主星质量之间的关系，并且到目前为止所得到的结果与径向速度程序的结果基本一致。
With now more than 20 exoplanets discovered by CoRoT, it has often been considered strange that so many of them are orbiting F-stars, and so few of them K or M-stars. Although transit search programs are mostly sensitive to short-period planets, they are ideal for verifying these results. To determine the frequency of planets as a function of stellar mass, we also have to characterize the sample of stars that was observed. We study the stellar content of the CoRoT-fields IRa01, LRa01 (=LRa06), and LRa02 by determining the spectral types of 11466 stars. We used spectra obtained with the multi-object spectrograph AAOmega and derived the spectral types by using template spectra with well-known parameters. We find that 34.8+/-0.7% of the stars observed by CoRoT in these fields are F-dwarfs, 15.1+/-0.5% G-dwarfs, and 5.0+/-0.3% K-dwarfs. We conclude that the apparent lack of exoplanets of K- and M-stars is explained by the relatively small number of these stars in the observed sample. We also show that the apparently large number of planets orbiting F-stars is similarly explained by the large number of such stars in these fields. Our study also shows that the difference between the sample of stars that CoRoT observes and a sample of randomly selected stars is relatively small, and that the yield of CoRoT specifically is the detection one hot Jupiter amongst 2100+/-700 stars. We conclude that transit search programs can be used to study the relation between the frequency of planets and the mass of the host stars, and that the results obtained so far generally agree with those of radial velocity programs.