Comparison of stellar radii found by multi-bant bolometric correction method with the values found by classical open cluster studies

Clusters are ideal laboratories for studies on star formation and evolution, as they are homogeneous groups of stars with similar chemical composition and age, formed from a cloud of gas and dust. Open clusters are important for studying the structure of the Milky Way, stellar populations in the Milky Way, star formation dynamics, and single and multiple star evolution. Determining the astrophysical parameters obtained from open cluster observations using sensitive and well-established methods is crucial for creating consistent and precise models of star formation and evolution. The absolute brightness of the stars in the open cluster is determined using colour-magnitude diagrams generated from photometric and astrometric data of the stars in the open cluster. Since the colours of the stars are also known, it is possible to proceed to their bolometric brightness. It is possible to proceed from bolometric brightness to luminosity and radius. In this thesis, it is aimed to obtain the radii by performing Spectral Energy Distribution (SED) analyses of the stars in the open cluster without obtaining the colour-magnitude diagram of the open cluster. This method, which we call the multi-bant bolometric correction method, was applied to an open cluster whose colour-magnitude diagram was obtained in the literature. In this thesis, the radii of the stars determined by these two different methods were compared using the stars of the selected NGC 6819 open cluster. This method used provided a more sensitive determination of star radii than the classical methods in the literature. Thus, a new method was developed for open clusters.