Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey

@misc{minniti2026unresolved,
  title = {{Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey}},
  author = {D. Minniti and T. Palma and C. O. Obasi and M. Gómez and R. K. Saito and J. G. Fernández-Trincado and J. Alonso-García and E. R. Garro and J. Corral-Santana and A. Luna and P. W. Lucas and M. G. Navarro and V. D. Ivanov and Z. Guo and J. Borissova and R. Kurtev and C. Morris and V. Fermiano and J. Osses and P. Esteves and C. Cáceres and B. Dias and S. Saroon and S. Federle and M. Lad and I. Petralia and P. Rodriguez Cuevas and J. B. Pullen and D. Bhadrakumar Sindhu and L. Gramajo and L. Baravalle and D. Galdeano and M. V. Alonso and J. L. Nilo Castellon},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.00659},
  eprint = {2610.00659},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.00659},
}

TY  - UNPB
TI  - Unresolved triples in the open cluster NGC 2437 (M 46) confirmed by the KMOS VVVX-GalCen Spectroscopic Survey
AU  - D. Minniti
AU  - T. Palma
AU  - C. O. Obasi
AU  - M. Gómez
AU  - R. K. Saito
AU  - J. G. Fernández-Trincado
AU  - J. Alonso-García
AU  - E. R. Garro
AU  - J. Corral-Santana
AU  - A. Luna
AU  - P. W. Lucas
AU  - M. G. Navarro
AU  - V. D. Ivanov
AU  - Z. Guo
AU  - J. Borissova
AU  - R. Kurtev
AU  - C. Morris
AU  - V. Fermiano
AU  - J. Osses
AU  - P. Esteves
AU  - C. Cáceres
AU  - B. Dias
AU  - S. Saroon
AU  - S. Federle
AU  - M. Lad
AU  - I. Petralia
AU  - P. Rodriguez Cuevas
AU  - J. B. Pullen
AU  - D. Bhadrakumar Sindhu
AU  - L. Gramajo
AU  - L. Baravalle
AU  - D. Galdeano
AU  - M. V. Alonso
AU  - J. L. Nilo Castellon
PY  - 2026
DA  - 2026/10/01
PB  - arXiv
DO  - 10.48550/arxiv.2610.00659
UR  - https://arxiv.org/abs/2610.00659
AB  - Recent optical and near-IR photometric databases like Gaia data release 3 (DR3) and the VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey allow the exploration of candidate unresolved multiple systems (binaries, triples, quadruples, etc.) in nearby clusters, that need spectroscopic confirmation. NGC 2437 (M 46) is a benchmark open cluster with well determined physical parameters. Its relative proximity (D=1.6 kpc) makes this cluster an ideal laboratory to measure 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. 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.
ER  -