Unresolved triple systems in the aged open cluster Trumpler 19: Discovery, confirmation, and implications

@misc{minniti2026unresolved,
  title = {{Unresolved triple systems in the aged open cluster Trumpler 19: Discovery, confirmation, and implications}},
  author = {D. Minniti and R. K. Saito and V. D. Ivanov and C. O. Obasi and M. Gómez and P. W. Lucas and J. G. Fernández-Trincado and J. Alonso-García and E. R. Garro and J. Corral-Santana and A. Luna and Z. Guo and R. Kurtev and J. Borissova and V. Fermiano and J. Osses and C. Morris and B. Dias and C. Cáceres and S. Saroon and J. B. Pullen and P. Rodriguez and M. Lad and S. Federle and I. Petralia and D. Bhadrakumar and P. Esteves and M. G. Navarro and T. Palma and L. Baravalle and D. Galdeano and M. V. Alonso and J. L. Nilo Castellon and A. N. Chené},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.05722},
  eprint = {2609.05722},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.05722},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Unresolved triple systems in the aged open cluster Trumpler 19: Discovery, confirmation, and implications
AU  - D. Minniti
AU  - R. K. Saito
AU  - V. D. Ivanov
AU  - C. O. Obasi
AU  - M. Gómez
AU  - P. W. Lucas
AU  - J. G. Fernández-Trincado
AU  - J. Alonso-García
AU  - E. R. Garro
AU  - J. Corral-Santana
AU  - A. Luna
AU  - Z. Guo
AU  - R. Kurtev
AU  - J. Borissova
AU  - V. Fermiano
AU  - J. Osses
AU  - C. Morris
AU  - B. Dias
AU  - C. Cáceres
AU  - S. Saroon
AU  - J. B. Pullen
AU  - P. Rodriguez
AU  - M. Lad
AU  - S. Federle
AU  - I. Petralia
AU  - D. Bhadrakumar
AU  - P. Esteves
AU  - M. G. Navarro
AU  - T. Palma
AU  - L. Baravalle
AU  - D. Galdeano
AU  - M. V. Alonso
AU  - J. L. Nilo Castellon
AU  - A. N. Chené
PY  - 2026
DA  - 2026/09/10
PB  - arXiv
DO  - 10.48550/arxiv.2609.05722
UR  - https://arxiv.org/abs/2609.05722
AB  - It is difficult to identify unresolved triple and higher-order systems beyond the solar vicinity. Star clusters yield controlled environments with known physical parameters, providing a way to explore homogeneous stellar samples. Combining modern optical and near-IR surveys, our main goal is to explore the region of the color-magnitude diagrams located above the sequence of equal-mass binaries, which is inhabited by unresolved triple and quadruple systems. Specifically, here we aim to discover and characterize the presence of multiple systems in the aged open star cluster Trumpler 19. We selected cluster members using Gaia astrometry and photometry from the VVVX and DECAPS2 surveys. We made optical and near-IR color-magnitude diagrams to select stars located >0.75 mag above the cluster main sequence, including suitable unresolved triple and quadruple systems. We confirm previous results that there is a sizable sequence of unresolved binaries in Trumpler 19. We also report the discovery of a sequence of unresolved multiple systems in this cluster, and confirm some of these multiple systems via radial velocities measured by the ESO KMOS VVVX-GalCen spectroscopic survey. The fraction of multiple stars in this cluster is comparable to that of the solar neighborhood, with the caveat that the local sample probes deeper down the main sequence. The fraction of unresolved triples and quadruples is also three times higher than that of the open cluster M 67, which is of a similar age and chemical composition. The discovery of unresolved triple systems in Trumpler 19 leads to our main conclusion that these systems were able to survive within the cluster for nearly 4 Gyr. In addition, this cluster contains more multiple systems than M 67, which has a similar total present mass. Further investigations are needed to unveil if this is a primordial feature or the result of dynamical evolution.
ER  -