Work

Southern Massive Stars at High Angular Resolution (SMaSH+): Properties of hierarchical massive triples

Year: 2026

Type: article

Abstract: Context. While massive stars are frequently found in triple architectures, the lack of observed parameter distributions has long remained a bottleneck for statistical models of their evolution. Aims. We bridge this gap by compiling the first representative set of physical and orbital distributions for main-sequence hierarchical massive triples. Methods. We present a homogeneous analysis of 26 O-type hierarchical triples identified in the SMaSH+ survey by combining spectroscopic data for inner binaries with interferometric and aperture masking detections of tertiary companions within ∼200 au. We derive the distributions of masses, mass ratios, and separations, and investigate their joint probability density functions. We assess the dynamical stability of these systems. We estimate the relative importance of secular processes by comparing the von Zeipel–Kozai–Lidov (ZKL) timescale to the general relativistic precession timescale for several systems with well-constrained orbital solutions. Finally, we evaluate the observational completeness and find no substantial detection bias for separations ≲100 au and mass ratios q out > 0.1. Results. The sample is dominated by strongly hierarchical configurations, consisting primarily of tight inner spectroscopic binaries ( a in < 1 au) and wider tertiaries ( a ∼ out / a in > 70 for most systems). We find no significant correlation between tertiary mass and either inner-binary mass or outer separation, indicating a broad diversity of system architectures. Ten systems (out of 26) host relatively massive tertiaries ( q out > 0.5), especially at closer outer separations ( a ∼ out ≲ 30 au). For two to four systems out of five with well-constrained orbits, general relativistic precession dominates over ZKL oscillations in their current configuration, although ZKL-driven migration may have contributed to the formation of the observed short-period inner binaries. These results provide the first observationally grounded distributions of key parameters for massive hierarchical triples and offer important constraints for population synthesis and evolutionary models, particularly regarding the role of tertiary companions in shaping binary evolution.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202557918