银河系核球中的一个候选高速系外行星系统
A Candidate High-Velocity Exoplanet System in the Galactic Bulge
AI总结：
针对微引力透镜事件MOA-2011-BLG-262的Keck AO图像分析确认其为银河系核球中宿主质量0.19M⊙、行星28.92M⊕、横向速度541.31km/s的高速系外行星系统，为迄今最高速且宿主质量最低的微引力透镜系外行星系统。
摘要：
我们对Keck-I望远镜针对微引力透镜事件MOA-2011-BLG-262的自适应光学（AO）图像进行了分析。Bennett等人2014年的原始发现论文报告了透镜系统的两种不同可能性：一种是带有系外卫星伴星的近邻气态巨行星透镜，另一种是银河系核球中带有行星伴星的极低质量恒星。微引力透镜事件与Keck后续观测之间约10年的基线，使我们能够探测到K=22.3星等的暗淡候选透镜宿主（恒星），并确认了遥远透镜系统的解释。结合宿主恒星亮度和光变曲线参数，得出宿主恒星质量为M_host=0.19±0.03M⊙，行星质量为m_p=28.92±4.75M⊕，距离为D_L=7.49±0.91 kpc。我们对Gaia DR3进行了多历元交叉参考，测量出候选透镜系统的横向速度为v_L=541.31±65.75 km s⁻¹。我们得出结论，该事件包含迄今为止探测到的速度最高的系外行星系统，也是首个通过确认质量测量得到的质量最低的微引力透镜宿主恒星。透镜系统的高速特性现在可以通过任何时间的额外高分辨率成像历元来明确确认。本工作概述的方法表明，Roman银河系系外行星巡天（RGES）将能够可靠地测量核球中的低质量宿主恒星。
英文摘要：
We present an analysis of adaptive optics (AO) images from the Keck-I telescope of the microlensing event MOA-2011-BLG-262. The original discovery paper by Bennett et al. 2014 reports two distinct possibilities for the lens system; a nearby gas giant lens with an exomoon companion or a very low mass star with a planetary companion in the galactic bulge. The $\sim$10 year baseline between the microlensing event and the Keck follow-up observations allows us to detect the faint candidate lens host (star) at $K = 22.3$ mag and confirm the distant lens system interpretation. The combination of the host star brightness and light curve parameters yields host star and planet masses of $M_{\rm host} = 0.19 \pm 0.03M_{\odot}$ and $m_p = 28.92 \pm 4.75M_{\oplus}$ at a distance of $D_L = 7.49 \pm 0.91\,$kpc. We perform a multi-epoch cross reference to \textit{Gaia} DR3 and measure a transverse velocity for the candidate lens system of $v_L = 541.31 \pm 65.75$ km s$^{-1}$. We conclude this event consists of the highest velocity exoplanet system detected to date, and also the lowest mass microlensing host star with a confirmed mass measurement. The high-velocity nature of the lens system can be definitively confirmed with an additional epoch of high-resolution imaging at any time now. The methods outlined in this work demonstrate that the \textit{Roman} Galactic Exoplanet Survey (RGES) will be able to securely measure low-mass host stars in the bulge.
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