The Evolution of Rotation and Magnetic Activity in 94 Aqr Aa from Asteroseismology with TESS

Abstract

Most previous efforts to calibrate how rotation and magnetic activity depend on stellar age and mass have relied on observations of clusters, where isochrones from stellar evolution models are used to determine the properties of the ensemble. Asteroseismology employs similar models to measure the properties of an individual star by matching its normal modes of oscillation, yielding the stellar age and mass with high precision. We use 27 days of photometry from the Transiting Exoplanet Survey Satellite to characterize solar-like oscillations in the G8 subgiant of the 94 Aqr triple system. The resulting stellar properties, when combined with a reanalysis of 35 yr of activity measurements from the Mount Wilson HK project, allow us to probe the evolution of rotation and magnetic activity in the system. The asteroseismic age of the subgiant agrees with a stellar isochrone fit, but the rotation period is much shorter than expected from standard models of angular momentum evolution. We conclude that weakened magnetic braking may be needed to reproduce the stellar properties, and that evolved subgiants in the hydrogen shell-burning phase can reinvigorate large-scale dynamo action and briefly sustain magnetic activity cycles before ascending the red giant branch.

14 pages including 8 figures and 3 tables (updated Table 3 & Figure 6). ApJ in press

References in corpus (16)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Southern Sample
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• ASTEC -- the Aarhus STellar Evolution Code
• A new correction of stellar oscillation frequencies for near-surface effects
• YREC: The Yale Rotating Stellar Evolution Code
• Mixed modes in red giants: a window on stellar evolution
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992
• The Stagger-grid: A grid of 3D stellar atmosphere models - III. The relation to mixing-length convection theory
• The Mount Wilson Observatory S-index of the Sun
• The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars
• K2P${}^2$ $-$ A photometry pipeline for the K2 mission
• The Asteroseismic Target List (ATL) for solar-like oscillators observed in 2-minute cadence with the Transiting Exoplanet Survey Satellite (TESS)
• Chemical Evolution in the Milky Way: Rotation-based ages for APOGEE-Kepler cool dwarf stars
• LBT/PEPSI Spectropolarimetry of a Magnetic Morphology Shift in Old Solar-type Stars

Cited by in corpus (15)

• A Catalogue of Solar-Like Oscillators Observed by TESS in 120-second and 20-second Cadence
• Magnetic and Rotational Evolution of $\rho$ CrB from Asteroseismology with TESS
• Magnetic activity evolution of solar-like stars: I. S_ph-Age relation derived from Kepler observations
• Asteroseismology and Spectropolarimetry of the Exoplanet Host Star $\lambda$ Serpentis
• KIC 7955301: a hierarchical triple system with eclipse timing variations and an oscillating red giant
• Luminaries in the Sky: The TESS Legacy Sample of Bright Stars. I. Asteroseismic detections in naked-eye main-sequence and sub-giant solar-like oscillators
• On the characterization of GJ 504: a magnetically active planet-host star observed by the Transiting Exoplanet Survey Satellite (TESS)
• A probabilistic method for detecting solar-like oscillations using meaningful prior information
• Fine Structure of the Age-Chromospheric Activity Relation in Solar-Type Stars: II. H$\alpha$ Line
• The TESS Mission Target Selection Procedure
• TESS asteroseismology of $\beta$ Hydri: a subgiant with a born-again dynamo
• Testing the Rossby Paradigm: Weakened Magnetic Braking in early K-type Stars
• Magnetic braking and dynamo evolution of $\beta$ Hydri
• Solar-like oscillations and ellipsoidal variations in TESS observations of the binary 12 Boötis
• Anti-Solar Differential Rotation May Have Revived Magnetic Braking in the Subgiant 31 Aquilae