Characterization of hot populations of Melotte 66 open cluster using <i>Swift</i>/UVOT

ABSTRACT Ultraviolet (UV) wavelength observations have made a significant contribution to our understanding of hot stellar populations star clusters. Multiwavelength spectral energy distributions (SEDs) stars, including ultraviolet observations, proven be an excellent tool for discovering unresolved companions in exotic stars such as blue straggler (BSS), thereby providing helpful clues constrain their formation mechanisms. Melotte 66 is 3.4 Gyr old open cluster located at distance 4810 pc. We identify the members by applying ML-MOC algorithm on Gaia EDR3 data. Based membership identification, we find 1162 members, 14 BSS candidates, 2 yellow candidates (YSS), and one subdwarf B candidate (sdB). generated SEDs 11 sdB using Swift/UVOT data combined with other archival optical IR wavelengths. discover companion candidate, BSS3, temperature 38 000$_{-6000}^{+7000}$ K, luminosity 2.99$_{-1.86}^{+5.47}$ L?, radius 0.04$_{-0.005}^{+0.008}$ R?. This likely low-mass WD estimated mass 0.24–0.44 M?. report BSS6, Algol-type eclipsing binary period 0.8006 d, based DR3 variability classification. suggest that BSS3 formed via either Case A or mass-transfer channel, whereas BSS6 transfer.