Revisit of open clusters UPK 39, UPK 41 and PHOC 39 : a new binary open cluster found

TL;DR

This study revisits three open clusters near the Aquila Rift, revealing that two are a primordial binary pair likely formed together, while the third may be captured in the future, based on Gaia and LAMOST data analysis.

Contribution

The paper provides a detailed analysis of three open clusters, identifying a new binary cluster pair and their formation history using Gaia DR3 and LAMOST data.

Findings

UPK 39 and UPK 41 are a primordial binary open cluster.

The clusters are approximately 6-8 million years old.

PHOC 39 may capture the binary pair in the future.

Abstract

We investigate the three open clusters near Aquila Rift cloud, named as UPK 39 (\texttt{c1} hereafter), UPK 41 (\texttt{c2} hereafter) in Sim et al. (2019) and PHOC 39 (\texttt{c3} hereafter) in Hunt \& Reffert (2021), respectively. Using photometric passpands, reddening, and extinction from Gaia DR3, we construct the color-absolute-magnitude diagram (CAMD). Using isochrone fits their ages are estimated as $6.3\pm0.9$, $8.1\pm1.4$ and $21.8\pm2.2$ Myr, respectively. Their proper motions and radial velocities, estimated using data from Gaia and LAMOST are very similar. From their orbits, relative distances among them at different times, kinematics, ages, and metallicities, we conclude that \texttt{c1} and \texttt{c2} are primordial binary open cluster, which are likely to have been formed at the same time, and \texttt{c3} may capture \texttt{c1}, \texttt{c2} in the future.