2026/04/14 by Marcus L. Marcussen, Mikkel N. Lund, Frank Grundahl +11 · 1 voice
Physics and Astronomy · #astro-ph.SR
μ Herculis is a bright, nearby quadruple system. Its brightest member, μ Her Aa, displays solar-like oscillations, establishing the system as a crucial benchmark for asteroseismology, provided that its mass can be determined independently of stellar models. We aim to resolve the full hierarchical architecture of the system and determine precise, model-independent dynamical masses for all four components (Aa, Ab, B, and C), along with a consistent astrometric solution for the system's centre of mass. We performed a joint fit of radial velocities, relative astrometry and absolute astrometry from Hipparcos, Gaia DR3, and ground-based catalogues, spanning nearly three centuries. Our forward-modelling framework simultaneously constrains the Keplerian orbits of the inner Aa--Ab and B--C subsystems, the wide A--BC orbit, and the sky motion and parallax of the total centre of mass. Leveraging several complementary datasets and the decisive 2023 periastron passage of the Aa--Ab pair, we precisely determine all orbital parameters and obtain sub-percent precision on the component masses: M\rm Aa = 1.134 ± 0.007 M\odot, M\rm Ab = 0.2286 ± 0.0006 M\odot, M\rm C = 0.445 ± 0.005 M\odot, and M\rm B = 0.417 ± 0.005 M\odot. We derive a system parallax of \varpi\rm CM = 120.069 ± 0.089 mas that reconciles and improves upon the individual Hipparcos and Gaia DR3 values.