UBVI CCD Photometry of Berkeley 55 Open Cluster

TL;DR

This study determines fundamental parameters of the Berkeley 55 open cluster using UBVI CCD photometry, confirming its distance, age, and location near the Perseus spiral arm, and comparing results with Gaia and Cepheid data.

Contribution

First detailed UBVI CCD photometric analysis of Be 55, deriving its fundamental parameters and comparing with Gaia and Cepheid distances.

Findings

Distance of 3.02 kpc consistent with Gaia and Cepheid data.

Age estimated at 85 million years.

Cluster located near the Perseus spiral arm.

Abstract

Fundamental astrophysical parameters have been derived for Be 55 open cluster based on UBVI CCD photometric data, observed with the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The mean reddening is obtained as E(B-V)=1.77+-0.10 mag from early type members. The zero age main sequence fitting in the Q(VA)- Q0 diagrams indicates the distance modulus, (V0 - MV)=12.4+-0.20 mag (d=3.02+-0.28 kpc). This photometric distance is consistent with the distances of Gaia EDR3 (d=3.09+-0.16 kpc) and period-luminosity relation (d=2.78+-0.32 kpc) of its Cepheid S5 within the uncertainties. This distance also locates the cluster near the Perseus spiral arm. The Geneva isochrone fittings to the Hertzsprung-Russell diagram and observational colourmagnitude diagrams derive turn-off age, 85+-13 Myr, by taking care five red supergiants/bright giants. The possible inconsistences on the locations of the bright giants with the rotating/non-rotating isochrones may be due to both the age spread of stars in young open clusters and the diversity in rotational velocities.