TESS Asteroseismology of α Mensae: Benchmark Ages for a G7 Dwarf and Its M Dwarf Companion

Chontos, A., et al.Asteroseismology of bright stars has become increasingly important as a method to determine the fundamental properties (in particular ages) of stars. The Kepler Space Telescope initiated a revolution by detecting oscillations in more than 500 main-sequence and subgiant stars. However, most Kepler stars are faint and therefore have limited constraints from independent methods such as long-baseline interferometry. Here we present the discovery of solar-like oscillations in α Men A, a naked-eye (V = 5.1) G7 dwarf in TESS's southern continuous viewing zone. Using a combination of astrometry, spectroscopy, and asteroseismology, we precisely characterize the solar analog α Men A (T eff = 5569 62 K, R ∗ = 0.960 0.016 R o˙, M ∗ = 0.964 0.045 M o˙). To characterize the fully convective M dwarf companion, we derive empirical relations to estimate mass, radius, and temperature given the absolute Gaia magnitude and metallicity, yielding M ∗ = 0.169 0.006 M o˙, R ∗ = 0.19 0.01 R o˙, and T eff = 3054 44 K. Our asteroseismic age of 6.2 1.4 (stat) 0.6 (sys) Gyr for the primary places α Men B within a small population of M dwarfs with precisely measured ages. We combined multiple ground-based spectroscopy surveys to reveal an activity cycle of P = 13.1 1.1 yr for α Men A, a period similar to that observed in the Sun. We used different gyrochronology models with the asteroseismic age to estimate a rotation period of ∼30 days for the primary. Alpha Men A is now the closest (d = 10 pc) solar analog with a precise asteroseismic age from space-based photometry, making it a prime target for next-generation direct-imaging missions searching for true Earth analogs.A.C. acknowledges support from the National Science Foundation under the Graduate Research Fellowship Program (DGE 1842402). D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379), and the National Science Foundation (AST-1717000). T.A.B. acknowledges support from a NASA FINESST award (80NSSC19K1424). A.S. is partially supported by MICINN project PRPPID2019-108709GBI00. V.S.A. acknowledges support from the Independent Research Fund Denmark (research grant 7027-00096B) and the Carlsberg Foundation (grant agreement CF19-0649). T.R.B. acknowledges support from the Australian Research Council (DP210103119). W.H.B., W.J.C., and M.B.N. thank the UK Science and Technology Facilities Council (STFC) for support under grant ST/R0023297/1. R.A.G. acknowledges the support of the PLATO and GOLF CNES grants. M.S.L. is supported by the Carlsberg Foundation (grant agreement No. CF17-0760). Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation (grant DNRF106). S.M. acknowledges support from the Spanish Ministry of Science and Innovation with Ramon y Cajal fellowship No. RYC-2015- 17697 and from grant No. PID2019-107187GB-I00. T.S.M. acknowledges support from NASA grant 80NSSC20K0458. Computational time at the Texas Advanced Computing Center was provided through XSEDE allocation TG-AST090107. R.H. D.T. acknowledges support from NSF grants ACI-1663696, AST1716436, and PHY-1748958 and NASA grant 80NSSC20K051