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arXiv 0912.2773astro-ph.EPastro-ph.SR
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围绕年轻活跃的K5V恒星BD +20 1790运行的大质量行星候选者的证据

Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790

M. Hernán-Obispo, M. C. Gálvez-Ortiz, G. Anglada-Escudé, S. R. Kane, J. R. Barnes, E. de Castro, M. Cornide

摘要:

BD+20 1790是一颗年轻、活跃、富含金属的晚型K5 Ve星。在过去的几年里,我们对这颗恒星的恒星活动和运动学进行了研究。先前的结果显示,尽管恒星的旋转速度适中,但恒星的活动水平很高,存在类似双折射的结构,表面上的斑点和强烈的耀斑事件。此外,还探测到径向速度变化,其半振幅高达1公里/秒。我们研究了这些径向速度变化的性质,以确定它们是由于恒星活动还是伴星引起的恒星反射运动。我们分析了高分辨阶梯光栅光谱,也得到了两个波段的光度,以产生光变曲线和确定光度周期。基于对平分线速度跨度的分析,以及色球指标的光谱指数,并考虑到光度分析,我们报告说,RV变化的最佳解释是存在一个亚恒星的同伴。RV数据的开普勒拟合产生了一个轨道周期为7.78天的近距离大质量行星的解决方案。近距离大质量行星的存在也可能是对探测到的高水平恒星活动的解释。由于RV数据不是行星搜索计划的一部分,我们可以将我们的结果视为行星伴侣的偶然证据。到目前为止,这是最年轻的主序星的行星候选人已报告。

英文摘要:

BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on the surface and strong flare events, despite the moderate rotational velocity of the star. In addition, radial velocity variations with a semi-amplitude of up to 1 km/s were detected. We investigated the nature of these radial velocity variations, in order to determine whether they are due to stellar activity or the reflex motion of the star induced by a companion. We have analysed high-resolution echelle spectra and also two-band photometry was obtained to produce the light curve and determine the photometric period. Based upon the analysis of the bisector velocity span, as well as spectroscopic indices of chromospheric indicators and taking into account the photometric analysis, we report that the best explanation for the RV variation is the presence of a sub-stellar companion. The Keplerian fit of the RV data yields a solution for a close-in massive planet with an orbital period of 7.78 days. The presence of the close-in massive planet could also be an interpretation for the high level of stellar activity detected. Since the RV data are not part of a planet search program, we can consider our results as a serendipitous evidence of a planetary companion. To date, this is the youngest main sequence star for which a planetary candidate has been reported.

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