Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
Year: 2026
Type: article
Abstract: Recent optical and near-IR photometric databases such as Data Release 3 (DR3) and the VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey allow for the exploration of candidate unresolved multiple systems (binaries, triples, quadruples, etc.) in nearby clusters, which need spectroscopic confirmation. Gaia NGC 2437 (M 46) is a benchmark open cluster with well-determined physical parameters. Its relative proximity (D=1.6 ± 0.1 kpc) makes it an ideal laboratory for measuring the fractions of unresolved multiple systems. We aim here to identify unresolved triple and higher-order systems that are reliable members of the open cluster NGC 2437, and provide the spectroscopic confirmation using radial velocities. The selection of cluster members was made using DR3 astrometry and optical photometry in combination with near-IR photometry from the VVVX survey. We made optical and near-IR color-magnitude diagrams to select stars located well above the cluster main sequence, which should include suitable unresolved multiple systems. Gaia We confirm that there is a sequence of unresolved binaries in NGC 2437, and report the discovery of a sequence of unresolved triple systems in this cluster. We corroborate membership for 13 binary systems and 8 triple systems using radial velocities measured by the ESO KMOS VVVX-GalCen spectroscopic survey. We further select stars with colors consistent with K-dwarfs, in order to have a controlled sample, comparable to the solar neighborhood. We also find that the fraction of unresolved triples and quadruples is higher than that of the older open cluster Trumpler 19, studied using a similar setup, suggesting that these systems merge to form blue stragglers or get dissolved with time. We report the spectroscopic confirmation of 95% of the selected VVVX targets, thereby securing the presence of a sequence of unresolved triple systems in NGC 2437, located above the sequence of equal-mass binaries. The single stars constitute 60 % of the mass of the cluster, while the rest of the mass (40 %) is lodged in the unresolved multiple systems.
Source: Astronomy and Astrophysics
Authors: D. Minniti, T. Palma, C. O. Obasi, R. K. Saito, J. G. Fernández-Trincado, J. Alonso-García, E. R. Garro, J. Corral-Santana, A. Luna, P. W. Lucas, M. G. Navarro, V. D. Ivanov, Z. Guo, J. Borissova, R. Kurtev, C. Morris, V. Fermiano, J. Osses, P. Esteves, C. Cáceres, B. Dias, S. Saroon, S. Federle, M. Lad, I. Petralia, P. Rodriguez Cuevas, J. B. Pullen, D. Bhadrakumar Sindhu, L. Gramajo, L. Baravalle, D. Galdeano, M. V. Alonso, J. L. Nilo Castellon
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
Awards: CONSTRAINING THE ORIGIN OF O-TYPE STARS THROUGH THEIR PROGENITOR IDENTIFICATION., G1503830331, G2141439436, The Nature and Origins of Eruptive Variability in YSOs, TRACKING DOWN THE ROOTS OF THE GLOBULAR CLUSTER - BLACK HOLE RELATION, G7610025757, UNVEILING THE HIDDEN GALACTIC PLANE A NEAR-INFRARED VIEW OF THE STELLAR POPULATIONS AND THE STAR CLUSTERS AT LOW-GALACTIC LATITUDES, G8461561985, CENTRO DE ASTROFISICA Y TECNOLOGIAS AFINES (CATA), G8890173333
OpenAlex ID: W7216103645