Spectral, kinematic, orbital dynamics and galactic origin analyses of metal-poor stars of intermediate spectral type in the solar neighborhood

This thesis study was conducted within the scope of the TÜBİTAK ARDEB 1001 project numbered 121F265, and includes spectral, kinematic, orbital dynamic, and age analyses of the stars BD +07 4841, BD -01 1792, HD 3546, and HD 148897, which were selected from the project's stellar sample. The high-resolution echelle spectra used for the determination of elemental abundances in the spectral analysis were obtained from the ESPaDOnS, SOPHIE, and UVES spectral libraries, respectively. For the astrometric data required in the kinematic calculations, the Gaia DR3 catalog was used. The derived alpha-element and iron (Fe) abundance ratios of the target stars were evaluated in comparison with Galactic population classifications based on stellar kinematics. In the calculation of the Galactic orbital parameters, recently developed Python libraries by the members of the HRSS High-Resolution Stellar Spectroscopy Fundamental Science Laboratory were utilized. For age determinations, the Bayesian-based method presented by Şahin and Bilir (2020) was adopted. The obtained chemical abundances were interpreted together with the orbital dynamics, ages, and kinematic properties to investigate the possible origins of the studied stars, particularly in the context of globular clusters and dwarf galaxies—potential satellite systems of the Milky Way. The orbital parameters, space velocities, and chemical abundance patterns of the target stars were jointly evaluated to investigate their likely Galactic origins. Notably, BD +07 4841 exhibits orbital and chemical properties closely matching those of the globular cluster Omega Centauri, suggesting a possible origin from this system. HD 3546 displays the low metallicity and enhanced alpha-element enrichment typical of thick-disk stars. In contrast, the high orbital eccentricities, frequent disk crossings, and alpha-enhanced abundance profiles of BD -01 1792 and HD 148897 indicate their membership in the Galactic halo population. These findings imply that a significant fraction of the analyzed stars may have been accreted from external systems during the Milky Way's hierarchical formation history. Stars of spectral types F and G retain the chemical imprint of their natal molecular clouds in their atmospheres. Therefore, the heavy element abundances observed in the atmospheres of such stars provide critical insights into the chemical evolution of the Galaxy. In particular, detailed studies of the spectral, kinematic, and orbital properties of intermediate-type stars located in the solar neighborhood contribute significantly to distinguishing among different Galactic stellar populations. However, studies that simultaneously evaluate the spectral, kinematic, and orbital dynamic properties of metal-poor stars in the solar neighborhood are relatively limited in the literature. Recent advances in analysis techniques and the emergence of large-scale sky survey programs have led to a growing number of such multidimensional studies. The analysis techniques applied in this thesis to the selected target stars are expected to make meaningful contributions to the literature on the chemical and dynamical structure of stars in the solar vicinity, particularly when applied to a statistically significant sample. Indeed, these methods have also been applied to a broader stellar sample consisting of 90 metal-poor G-type stars with metallicities in the range -2.5 < [Fe/H] (dex) < -0.5, as part of the same TÜBİTAK ARDEB 1001 project. Notably, 66% of this sample consists of stars with high proper motion (mu > 100 mas/yr). The four stars analyzed in this thesis — BD +07 4841, BD -01 1792, HD 3546, and HD 148897 — are representative high proper motion stars selected from this group and exhibit metal-poor characteristics. Almost all the targets examined in this study show differences in reported values of effective temperature, surface gravity, and metallicity compared to those found in the literature, and are being analyzed for the first time in such a comprehensive framework combining spectral, kinematic, and orbital dynamic methods.