基于LAMOST DR13与Gaia DR3的贫金属巨星测光距离及超高速星搜寻
Photometric Distances for Metal-poor Giants and a Search for Hypervelocity Stars with LAMOST DR13 and Gaia DR3
AI总结：
本研究结合LAMOST DR13光谱与Gaia DR3天体测量数据，校准贫金属巨星测光距离关系，据此搜寻到9颗贫金属超高速星候选体，其中1颗或起源于银盘，3颗或与人马座星流相关。
AI中文摘要：
超高速星（HVS）是速度足以逃离银河系的恒星，其认证高度依赖距离估计，尤其是遥远巨星的距离。本研究结合LAMOST DR13光谱数据与Gaia DR3天体测量数据，搜寻贫金属超高速星候选体。利用高质量参考样本，校准得到贫金属巨星的金属丰度依赖的色-绝对星等关系，将其应用于41331颗恒星以推导测光距离；该关系重现参考绝对星等的弥散为0.24星等，对应固有距离不确定度约9.7%。结合上述距离、Gaia自行及LAMOST视向速度，在McMillan（2017）的银河系势场下，初步识别出13颗初始不被引力束缚的候选体。光谱检查显示，其中部分为色球活跃双星或其他非标准系统，此类系统的巨星校准不可靠；剔除这些干扰后，剩余9颗贫金属超高速星候选体。反向轨道积分表明，1颗候选体最符合银盘起源，3颗的轨道轨迹暗示与人马座星流存在关联。
英文摘要：
Hypervelocity stars (HVSs) are stars with velocities high enough to escape the Milky Way, but their identification depends sensitively on distance estimates, particularly for distant giants. In this work, we search for metal-poor HVS candidates by combining LAMOST DR13 spectroscopy with Gaia DR3 astrometry. We calibrate a metallicity-dependent color--absolute-magnitude relation for normal metal-poor giants using a high-quality reference sample, and apply it to derive photometric distances for 41{,}331 stars. The relation reproduces the reference absolute magnitudes with a scatter of 0.24\,mag, corresponding to an intrinsic distance uncertainty of $\sim$9.7\%. Combining these distances with Gaia proper motions and LAMOST radial velocities, we identify 13 initially unbound candidates under the Galactic potential from \citet{McMillan2017}. Spectral inspection indicates that several are chromospherically active binaries or other non-standard systems for which a giant-star calibration is unreliable; removing these contaminants leaves nine metal-poor HVS candidates. Backward orbit integrations suggest that one candidate is most consistent with a disk origin, while three have trajectories suggestive of an association with the Sagittarius stream.
