标题： 可见光和近红外波段对迷你月球2024 PT$_5$的多历元光谱测光表征 显示英文标题

标题： Multi-epoch spectro-photometric characterization of the minimoon 2024 PT$_5$ in the visible and near-infrared

摘要： 2024 PT$_5$是一颗小型（$D\leq10$m）近地小行星（NEA），于2024年8月被发现。 2024 PT$_5$在2024年9月至11月期间与地月系统存在引力束缚，被归类为迷你月球。 一些快速响应观测表明2024 PT$_5$来源于月球喷出物，而旋转状态和反照率是研究其起源的关键属性，但目前尚未得到很好约束。 我们利用Seimei 3.8米望远镜上的TriColor CMOS相机和光谱仪（TriCCS）在2025年1月4日至10日期间获取的数据，对2024 PT$_5$进行了可见光至近红外多色测光。 2024 PT$_5$的赛名/TriCCS 观测覆盖相位角从14度到27度，并在Pan-STARRS系统中的$g$、$r$、$i$和$z$波段中获得。 此外，我们分析了使用凯克I望远镜上的多目标红外探索光谱仪（MOSFIRE）于2025年1月16-17日获取的$Y$、$J$、$H$和$K$光度数据。 我们的光变曲线显示在几十分钟的时间尺度上有亮度变化。 我们推断2024 PT$_5$处于翻滚状态，光变曲线振幅约为0.3星等。 可见光和近红外颜色指数的2024 PT$_5$, $g-r=0.567\pm0.044$, $r-i=0.155\pm0.009$, $r-z=0.147\pm0.066$, $Y-J=0.557\pm0.046$, $J-H=0.672\pm0.078$, 和 $H-Ks=0.148\pm0.098$，表明2024 PT$_5$是一个S型小行星，与之前的观测结果基本一致。 使用$H$-$G$模型，我们推导出 V 波段的绝对星等$H_{V,HG}$为$27.72\pm0.09$和斜率参数$G_V$为$0.223\pm0.073$。 从其光度相位曲线的斜率得出2024 PT$_5$的几何反照率为$0.26\pm0.07$。这个反照率值是S型和Q型近地天体的典型值。根据我们的观测得出的2024 PT$_5$的颜色特性与从月球表面采集的岩石样本相匹配，这与之前的研究一致。 显示英文摘要

摘要： 2024 PT$_5$ is a tiny ($D\leq10$ m) near-Earth asteroid (NEA) discovered in August 2024. 2024 PT$_5$ was gravitationally bound to the Earth-Moon system from September to November 2024 and classified as a minimoon. Several quick response observations suggest the lunar ejecta origin of 2024 PT$_5$, while rotation state and albedo, essential properties to investigate its origin, are not well constrained. We performed visible to near-infrared multicolor photometry of 2024 PT$_5$ from data taken using the TriColor CMOS Camera and Spectrograph (TriCCS) on the Seimei 3.8 m telescope during 2025 January 4-10. The Seimei/TriCCS observations of 2024 PT$_5$ cover phase angles from 14 deg to 27 deg, and were obtained in the $g$, $r$, $i$, and $z$ bands in the Pan-STARRS system. In addition, we analyzed $Y$, $J$, $H$, and $K$ photometry taken with the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) on the Keck I 10-m telescope taken on 2025 January 16-17. Our lightcurves show brightness variations over time periods of several tens of minutes. We infer that 2024 PT$_5$ is in a tumbling state and has a lightcurve amplitude of about 0.3 mag. Visible and near-infrared color indices of 2024 PT$_5$, $g-r=0.567\pm0.044$, $r-i=0.155\pm0.009$, $r-z=0.147\pm0.066$, $Y-J=0.557\pm0.046$, $J-H=0.672\pm0.078$, and $H-Ks=0.148\pm0.098$, indicate that 2024 PT$_5$ is an S-complex asteroid, largely consistent with previous observations. Using the $H$-$G$ model, we derived an absolute magnitude $H_{V,HG}$ of $27.72\pm0.09$ and a slope parameter $G_V$ of $0.223\pm0.073$ in V-band. A geometric albedo of 2024 PT$_5$ is derived to be $0.26\pm0.07$ from the slope of its photometric phase curve. This albedo value is typical of the S- and Q-type NEAs. The color properties of 2024 PT$_5$ derived from our observations match rock samples taken from the lunar surface, which agrees with previous studies.