Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of 0.3 Jupiter-mass, an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the radial velocity variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary temperature of approximately 230 K. The star has a metallicity of [Fe/H] = 0.32+/-0.06 dex, of order twice solar and among the highest metallicity stars in the immediate solar neighborhood. This newly discovered planet provides further support that the well-known planet-metallicity correlation for F, G, and K stars also extends down into the M-dwarf regime. The a priori geometric probability for transits of this planet is only about 1%. However, the expected eclipse depth is ~7%, considerably larger than that yet observed for any transiting planet. Though long on the odds, such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with HST. At the expected planetary effective temperature, the atmosphere may contain water clouds.
Stacked Periodograms as a Probe of Exoplanetary Populations
正在进行的极高精度多普勒径向速度巡天寻找质量小于几个M $_\oplus$的行星;然而，由于所需的观测时间投资以及与强有力地探测最低质量行星有关的挑战，确定行星质量分布的人口水平研究仍然很困难。我们概述了一种新的方法，利用广泛的，现有的RV数据集来约束群众的系外行星种群：堆叠周期图RV时间序列在许多目标。我们表明，一个系外行星人口可能是统计上可识别的堆叠周期图，即使个别行星不通过检测的阈值。我们讨论的堆叠周期图的分析，统计特性，进行模拟，以证明该方法的有效性，并调查半结构化的窗口函数和恒星活动的影响。对利克-卡内基系外行星巡天数据集的分析揭示了一个轻微显著的（$1.6σ$）信号，该信号与占据$3-7$日周期的系外行星群一致，其典型的$K$介于$1.6-5.1$ m s $^{-1}$之间。可能需要对与恒星活动和年度系统学相关的信号进行更详细的调查，以确认这一结果或检测其他潜在的开普勒贡献。
An Outer Giant Planet or Brown Dwarf in the 51 Pegasi System?
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；University of Hawai’i at Mänoa（夏威夷大学马诺阿分校）；Yale University（耶鲁大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of California Los Angeles（加州大学洛杉矶分校）；Michigan State University（密歇根州立大学）
