CCD UBVRI photometry of the open cluster Berkeley 8

Hikmet Çakmak ,Raul Michel ,Yusuf Karataş

doi:10.3906/fiz-1906-6

Abstract

The poorly studied Berkeley 8 (Be 8) open cluster is analyzed from CCD U BV RI photometric data taken with the 0.90 m telescope at the Sierra Nevada Observatory. The Z = +0.008 PARSEC isochrone gave us a reddening of E(B-V) = 0.69 ± 0.03, a distance of 3410 ± 300 pc, and an age of 2.8 ± 0.2 Gyr. Its median Gaia DR2 distance, d = 3676 ± 810 pc, is in good agreement with our photometric distances, 3410-3620 pc within the uncertainties. The kinematic parameters of five likely members of Be 8 with the circular orbits, ecc = [0.23, 0.30] , reflect the properties of the Galactic thin disc, which is also consistent with what is expected of its metal content ([M/H] = -0.27). Be 8 with R > 9 kpc (co-rotation gap at 9 kpc) may have been originating from a different galactic radius or different star formation region.

Highlights

Open clusters (OCs) are valuable objects for revealing stellar evolution and the structure, chemical, and dynamical evolution of the Galactic disc
The main aim of this paper is to present astrophysical parameters such as reddening, distance, and age of Berkeley 8 (Be 8) from four color indices, (B − V ), (V − I), (R − I), and (GBP – GRP ), obtained from deep CCD U BV RI and Gaia photometries
This kind of data is valuable for classifying early-type stars, Blue Stragglers (BS), and Red Giant/Red Clump (RG/RC) candidates in the color magnitude diagrams (CMDs), and probable candidates are proposed for future spectroscopic observations

Summary

Introduction

Open clusters (OCs) are valuable objects for revealing stellar evolution and the structure, chemical, and dynamical evolution of the Galactic disc. 4. Classification of cluster members For the membership determination of Be 8, our CCD U BV RI photometric data have been matched with Gaia DR2 astrometric (proper motion components and parallaxes) ( μα , μδ , and π ) and Gaia DR2 photometric data. By applying the Gaussian Mixture Model (GMM) [20] to the stars in the cluster region of Be 8, we have determined the membership probability ( P ). The used parameters for estimation of Φc and Φf are μα , μδ , π , σμα , σμδ , and σπ From the relation of the membership probability ( P ) versus G mag (Figure 6b), high membership probability appears to extend down to G ∼ 21 mag

Astrophysical parameters of Be 8 open cluster

Findings

Discussion and conclusions