UOCS. III. UVIT catalogue of open clusters with machine learning based
  membership using \textit{Gaia} EDR3 astrometry
  We present a study of six open clusters (Berkeley 67, King 2, NGC 2420, NGC
2477, NGC 2682 and NGC 6940) using the Ultra Violet Imaging Telescope (UVIT)
aboard \textit{ASTROSAT} and \textit{Gaia} EDR3. We used combinations of
astrometric, photometric and systematic parameters to train and supervise a
machine learning algorithm along with a Gaussian mixture model for the
determination of cluster membership. This technique is robust, reproducible and
versatile in various cluster environments. In this study, the \textit{Gaia}
EDR3 membership catalogues are provided along with classification of the stars
as \texttt{members, candidates} and \texttt{field} in the six clusters. We
could detect 200--2500 additional members using our method with respect to
previous studies, which helped estimate mean space velocities, distances,
number of members and core radii. UVIT photometric catalogues, which include
blue stragglers, main-sequence and red giants are also provided. From
UV--Optical colour-magnitude diagrams, we found that majority of the sources in
NGC 2682 and a few in NGC 2420, NGC 2477 and NGC 6940 showed excess UV flux.
NGC 2682 images have ten white dwarf detection in far-UV. The far-UV and
near-UV images of the massive cluster NGC 2477 have 92 and 576 \texttt{members}
respectively, which will be useful to study the UV properties of stars in the
extended turn-off and in various evolutionary stages from main-sequence to red
clump. Future studies will carry out panchromatic and spectroscopic analysis of
noteworthy members detected in this study.
