We report radial-velocity search for short-period planets in the Pleiades open cluster. We observed 30 Pleiades member stars at the Okayama Astrophysical Observatory (OAO) with High Dispersion Echelle Spectrograph (HIDES). To evaluate and mitigate the effects of stellar activity on radial-velocity measurements, we computed four activity indicators (FWHM, $V_{\rm span}$, $W_{\rm span}$ and $S_{\rm H{\alpha}}$). Among our sample, no short-period planet candidates were detected. Stellar intrinsic RV jitter was estimated to be ${\rm 52\ m\,s^{-1}}$, ${\rm 128\ m\,s^{-1}}$ and ${\rm 173\ m\,s^{-1}}$ for stars with $v\sin i$ of ${\rm 10\ km\,s^{-1}}$, ${\rm 15\ km\,s^{-1}}$ and ${\rm 20\ km\,s^{-1}}$, respectively. We determined the planet occurrence rate from our survey and set the upper limit to 11.4\% for the planets with masses 1--13 $M_{\rm JUP}$ and period 1--10 days. To set a more stringent constraint on the planet occurrence rate, we combined the result of our survey with those of other surveys targeting open clusters with ages between 30--300 Myr. As a result, the planet occurrence rate in young open clusters was found to be less than 7.4\%, 2.9\% and 1.9\% for the planets with an orbital period of three days and masses between 1--5, 5--13, and 13--80 $M_{\rm JUP}$, respectively.

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昴宿星团疏散星团中短周期行星的径向速度搜索和统计研究

我们报告了昴宿星团疏散星团中短周期行星的径向速度搜索。我们在冈山天体物理天文台 (OAO) 使用高色散阶梯光谱仪 (HIDES) 观测了 30 颗昴宿星团成员恒星。为了评估和减轻恒星活动对径向速度测量的影响，我们计算了四个活动指标（FWHM、$V_{\rm span}$、$W_{\rm span}$ 和 $S_{\rm H{\alpha }}$）。在我们的样本中，没有检测到短期行星候选者。Stellar 固有 RV 抖动估计为 ${\rm 52\ m\,s^{-1}}$、${\rm 128\ m\,s^{-1}}$ 和 ${\rm 173\ m\,s^{-1}}$ 表示 $v\sin i$ 为 ${\rm 10\ km\,s^{-1}}$, ${\rm 15\ km\,s^ {-1}}$ 和 ${\rm 20\ km\,s^{-1}}$ 分别。我们根据调查确定了行星出现率，并将上限设置为 11。4\% 质量为 1--13 $M_{\rm JUP}$ 且周期为 1--10 天的行星。为了对行星出现率设置更严格的限制，我们将我们的调查结果与其他针对年龄在 30--300 Myr 之间的疏散星团的调查结果相结合。结果发现，对于公转周期为三天、质量在1--5、5--之间的行星，年轻疏散星团中的行星出现率分别低于7.4\%、2.9\%和1.9\%。分别为 13 和 13--80 $M_{\rm JUP}$。