Host Star Metallicity Across Different Exoplanet Populations: A Statistical Analysis Using LAMOST Spectroscopic Data

The formation and diversity of exoplanets are influenced by both physical and chemical properties of their host stars, making statistical comparisons of host stars an important approach to understanding how planetary systems differ. In this study, we combine medium-resolution spectroscopic data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) with confirmed exoplanet information from the NASA Exoplanet Archive to construct samples of exoplanet host stars and a matched control sample of stars without known planets. Using uniform data selection and statistical analysis, we examine stellar parameters with particular emphasis on metallicity and compare host stars associated with different types of exoplanets. We find that host stars and control stars are generally similar in effective temperature and evolutionary stage, indicating that they belong to comparable stellar populations, but they show differences in metallicity distributions. Gas giant planets are preferentially found around metal-rich stars, while terrestrial planets and sub-Neptunes occur over a much broader range of metallicities. For the low-mass planet sample, planetary mass and radius exhibit a weak positive trend with host star metallicity, although this result is limited by small sample size and should be interpreted with caution. Overall, this work provides statistical observational evidence that host star metallicity is related to exoplanet type, particularly for massive planets, and demonstrates that medium-resolution spectroscopic surveys such as LAMOST are valuable resources for large-sample studies of exoplanet host stars.