Long-term investigation of an open cluster Berkeley 65

Tarak Chand; Saurabh Sharma; Koshvendra Singh; Jeewan Pandey; Aayushi Verma; Harmeen Kaur; Mamta; Manojit Chakraborty; Devendra K. Ojha; Ajay Kumar Singh

doi:10.3389/fspas.2025.1608196

paper

Long-term investigation of an open cluster Berkeley 65

arXiv:2505.24240 · doi:10.3389/fspas.2025.1608196

Abstract

We present a decade-long investigation of a poorly studied cluster, Berkeley 65 (Be 65), using deep optical data from the telescopes of ARIES, Nainital Observatory. We estimate its radius ( $R_{c l u s t er}$ = 1.6 $^{^{'}}$ , aspect ratio of $\sim$ 1.1), distance (2.0 $\pm$ 0.1 kpc) and age ( $\sim$ 160 Myrs). A clear turn-off point at $\sim$ 1.7 M $_{⊙}$ in the mass function suggests the escape of low-mass stars, and the lower photometric mass compared to the dynamical mass indicates ongoing disruption due to external forces. Our long-baseline optical photometric data also identifies 64 periodic and 16 non-periodic stars in this region. We have presented the light curves and the classification of those variables. The periodic stars have periods ranging from $\sim$ 0.05 days to $\sim$ 3.00 days and amplitude ranges from $\sim$ 8 mmag to $\sim$ 700 mmag. The nonperiodic stars show variation from $\sim$ 30 mmag to $\sim$ 500 mmag. The periodic stars include main-sequence pulsating variables such as Slow Pulsating B-type, $δ$ Scuti, RR Lyrae, and $γ$ Doradus. We report a detached binary system and rotating variables similar to BY Draconis-type stars exhibiting variable brightness caused by starspots, chromospheric activity, and magnetic field-related phenomena.

28 pages, 10 figures, 2 tables, accepted in Frontiers in Astronomy and Space Sciences

Long-term investigation of an open cluster Berkeley 65

Abstract

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