Merging high resolution spectroscopy with accurate photometry in the study of open clustersBeeson, Kevin (Avtor) Kos, Janez (Mentor) open clusters and associations: general -- techniques: photometric-- parallaxes -- Hertzsprung –Russell and colour–magnitude diagrams -- stars: abundancesThe study of stars' chemical composition is pivotal for understanding the Milky Way's history. The explosion of large astronomical surveys in the 21$^{\rm{st}}$ century gives a wealth of data for astronomers to explore with the improving observational analytical methods. In this thesis, we combined photometric methods with spectroscopic methods to get better chemical compositions of stars in open clusters. The ability to measure precise and accurate stellar effective temperatures ($T_{\rm{eff}}$) and surface gravities ($\log(g)$) is essential in determining accurate and precise abundances of chemical elements in stars. Measuring $\log(g)$ from isochrones fitted to colour-magnitude diagrams of open clusters is significantly more accurate and precise compared to spectroscopic $\log(g)$. By determining the ranges of ages, metallicity, and extinction of isochrones that will fit the colour-magnitude diagram, we constructed a joint probability distribution of $T_{\rm{eff}}$ and $\log(g)$. The joint photometric probability shows the complex correlations between $T_{\rm{eff}}$ and $\log(g)$, which depend on the evolutionary stage of the star. We show that by using this photometric prior while fitting spectra, we can acquire more precise spectroscopic stellar parameters and abundances of chemical elements. This reveals higher-order abundance trends in open clusters like traces of atomic diffusion. We used photometry and astrometry provided by the \textit{Gaia} DR3 catalogue, Padova isochrones, and Galactic Archaeology with HERMES (GALAH) DR4 spectra. We analysed the spectra of 1979 stars in nine open clusters, using Markov chain Monte Carlo(MCMC) to fit the spectroscopic abundances of 26 elements, $T_{\rm{eff}}$, $\log(g)$, $v_{\rm{mic}}$, and $v_{\rm{broad}}$. We found that using photometric priors improves the accuracy of abundances and $\log(g)$, as we observed the effects of atomic diffusion in certain elements when we calculated abundances using photometric priors, compared to calculations made without the photometric priors. We explored how well MCMC measures the precision of abundances and stellar parameters by comparing them to abundance spread in repeat observations, abundance spread in M67, and the uncertainty in GALAH DR4. We found that MCMC underestimates the precision of abundances. We compared our precision to GALAH DR4 and found it to be well-measured.20242024-09-26 08:15:15Doktorsko delo/naloga162660VisID: 144371COBISS_ID: 209918979sl