Hot Stellar Populations of Berkeley 39 Using Swift/UVOT

Abstract

Open clusters are excellent tools to probe the history of the Galactic disk and properties of star formation. In this work, we present a study of an old age open cluster Berkeley 39 using the observations from UVOT instrument of the Neil Gehrels Swift observatory. Making use of a machine learning algorithm, ML-MOC, we have identified a total of 861 stars as cluster members out of which 17 are blue straggler stars. In this work, we present a characterisation of two blue straggler stars. To estimate the fundamental parameters of blue straggler stars and their companions (if any), we constructed spectral energy distributions using UV data from Swift/UVOT and GALEX, optical data from Gaia DR3, and infrared (IR) data from 2MASS, Spitzer/IRAC, and WISE. We find excess flux in UV in one blue straggler star, implying the possibility of a hot companion.