[Paper Review] TESS Asteroseismology of $\alpha$ Mensae: Benchmark Ages for a G7 Dwarf and its M-dwarf Companion

Ashley Chontos, Daniel Huber+24 more|arXiv (Cornell University)|Dec 19, 2020

Stellar, planetary, and galactic studies11 references4 citations

TL;DR

This study presents the first precise asteroseismic age (6.2 ± 1.4 Gyr) for α Mensae A, a bright G7 dwarf, using TESS photometry combined with spectroscopy and astrometry. It also derives empirical mass-radius-temperature relations for its M-dwarf companion, establishing the system as a benchmark for gyrochronology and stellar age calibration in low-mass stars.

ABSTRACT

Asteroseismology of bright stars has become increasingly important as a method to determine 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 $\alpha$ 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 alpha Men A (Teff = 5569 +/- 62 K, R = 0.960 +/- 0.016 Rsun, M = 0.964 +/- 0.045 Msun). 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, R = 0.19 +/- 0.01 and Teff = 3054 +/- 44 K. Our asteroseismic age of 6.2 +/- 1.4 (stat) +/- 0.6 (sys) Gyr for the primary places $\alpha$ 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 13.1 +/- 1.1 years, 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=10pc) 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.

Motivation & Objective

• To determine the precise asteroseismic age of α Mensae A, a bright solar-analogue G7 dwarf, using TESS photometry.
• To characterize the M-dwarf companion using empirical relations derived from Gaia absolute magnitude and metallicity.
• To investigate long-term magnetic activity cycles in α Mensae A using multi-epoch spectroscopy.
• To calibrate gyrochronology models using the asteroseismic age and estimated rotation period.
• To establish the α Mensae system as a benchmark for future direct imaging missions targeting Earth-like planets.

Proposed method

• Acquired TESS 2-minute cadence photometry to detect solar-like oscillations in α Mensae A.
• Combined asteroseismic modeling with spectroscopic and astrometric data to derive fundamental stellar parameters (Teff, R*, M*).
• Used empirical relations between Gaia absolute magnitude, metallicity, and stellar properties to estimate mass, radius, and temperature for the M-dwarf companion.
• Applied gyrochronology models (standard and weakened braking laws) to estimate rotation periods from the asteroseismic age.
• Analyzed ground-based spectroscopic surveys to detect a 13.1 ± 1.1 year activity cycle in α Mensae A.
• Validated results using multiple stellar evolution codes (e.g., MESA, GARSTEC) and Bayesian inference (emcee, isoclassify).

Experimental results

Research questions

• RQ1 What is the asteroseismic age of the G7 dwarf α Mensae A, and how precise is it?
• RQ2 Can empirical relations accurately estimate mass, radius, and temperature for the fully-convective M-dwarf companion using Gaia data?
• RQ3 Does α Mensae A exhibit a long-term magnetic activity cycle, and how does its period compare to the Sun’s?
• RQ4 What is the estimated rotation period of α Mensae A based on gyrochronology and the asteroseismic age?
• RQ5 How does the α Mensae system serve as a benchmark for calibrating stellar age-dating methods in low-mass stars?

Key findings

• The asteroseismic age of α Mensae A is 6.2 ± 1.4 (stat) ± 0.6 (sys) Gyr, making it the closest (d = 10 pc) solar-analogue with a precise space-based asteroseismic age.
• The M-dwarf companion has a mass of 0.169 ± 0.006 M⊙, radius of 0.19 ± 0.01 R⊙, and effective temperature of 3054 ± 44 K, derived from empirical relations.
• A long-term magnetic activity cycle of P = 13.1 ± 1.1 years was detected in α Mensae A, similar in period to the Sun’s 11-year cycle.
• Gyrochronology models yield rotation periods of 30.4 ± 4.5 days (standard braking) and 29.6 ± 3.0 days (weakened braking), consistent with the asteroseismic age.
• The system is now a key benchmark for calibrating gyrochronology and improving age estimates for late-type stars.
• The combination of precise age, activity cycle, and rotation period positions α Mensae A as a prime target for next-generation direct imaging missions.