2025MNRAS.537.1763R

This study focuses on the open cluster NGC 6834. Despite being well-known, its primary parameters show considerable variation. As an intermediate-age cluster (50-80 million years), it is expected to host a prominent population of B-type stars, including numerous Be stars. Fifteen B-type variable stars have already been identified in the vicinity of the cluster, with four confirmed as Be stars through spectroscopic observations. Our spectrophotometric analysis aims to better understand the general and specific properties of NGC 6834, with particular emphasis on its B-type stars. Photometric data were gathered from gri images obtained with the Gemini North telescope, which was completed with several photometric catalogues. Additionally, 109 optical spectra for 89 stars in the cluster's region were obtained using the GMOS-MOS spectrograph. From the photometric data, we derive the foreground cluster colour excess, E(B - V) = 0.62. Through photometric diagrams, including traditional colour-colour and colour-magnitude diagrams and those incorporating the reddening-free Q parameter, we identify new stars with $\mathrm{H}\alpha$ emission. Spectral classification of 89 stars is achieved, along with estimations of basic physical parameters, and projected rotational velocities for 64 B-type stars. We identify five new Be stars: NGC 6834 3, 9, and 118 as cluster members, and NGC 6834 23 and 121 as non-members. The research contributes to a deeper understanding of the structure of NGC 6834 and its B-type star population.