Identification of unresolved binaries in the VVV b294 tile: A Pro-Am collaboration using the Virtual Observatory

Abstract

Stellar binaries and multiples are common objects. Their identification and characterization are primarily limited by the angular resolution of current instrumentation, survey depth and dynamic range. Towards the Galactic plane, stellar crowding further complicates these studies. We aim to identify unresolved binaries with good astrometric solutions and M dwarf primaries in the b294 field from the Vista Variables in the V\'ia L\'actea (VVV) survey using publicly available data. We examine the catalogue of M dwarfs within 500 pc in the b294 tile, employing binarity tracers based on statistical parameters from Gaia Data Release 3, multi-band photometry, and information in the literature. We reassess the astrometric and photometric parameters typically used for binary detection, establishing new boundaries and validating existing ones in the dense stellar field examined. We compare these results with those obtained in the solar vicinity. We present 990 unresolved binary candidates and 43 previously known binaries, including five possible triple systems. These represent the 13\% of the catalogue, rising to 14.9\% in well-covered regions. Binary-model SED fitting yields effective temperatures for 98 primary stars, with the properties of their secondary candidates indicating that nearly half may be substellar objects. We select 120 of the most promising binary candidates. Tangential velocities, where calculated, place 95\% of the studied binary candidates within the young disc population (tau <= 1 Ga). We demonstrate that the influence of nearby Gaia detections on the statistical parameters is small, allowing constraints similar to those that are applied in less crowded regions.