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

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  • Travis S. Metcalfe
  • Jennifer L. Van Saders, University of Hawaii at Manoa
  • ,
  • Sarbani Basu, Yale University
  • ,
  • Derek Buzasi, Florida Gulf Coast University
  • ,
  • William J. Chaplin, University of Birmingham
  • ,
  • Ricky Egeland, National Center for Atmospheric Research
  • ,
  • Rafael A. Garcia, Universite Paris-Saclay
  • ,
  • Patrick Gaulme, Max Planck Institute for Solar System Research
  • ,
  • Daniel Huber, University of Hawaii at Manoa
  • ,
  • Timo Reinhold, Max Planck Institute for Solar System Research
  • ,
  • Hannah Schunker, Max Planck Institute for Solar System Research, University of Newcastle
  • ,
  • Keivan G. Stassun, Vanderbilt University
  • ,
  • Thierry Appourchaux, Universite Paris-Sud
  • ,
  • Warrick H. Ball, University of Birmingham
  • ,
  • Timothy R. Bedding, University of Sydney
  • ,
  • Sébastien Deheuvels, Universite Toulouse III - Paul Sabatier
  • ,
  • Lucía González-Cuesta, Instituto Astrofisico de Canarias, University of La Laguna
  • ,
  • Rasmus Handberg
  • Antonio Jiménez, Instituto Astrofisico de Canarias, University of La Laguna
  • ,
  • Hans Kjeldsen
  • Tanda Li, University of Sydney, Chinese Academy of Sciences
  • ,
  • Mikkel N. Lund
  • Savita Mathur, Instituto Astrofisico de Canarias, University of La Laguna
  • ,
  • Benoit Mosser, Laboratoire de Géologie de l’ENS - PSL Research University – CNRS UMR8538
  • ,
  • Martin B. Nielsen, University of Birmingham, New York University Abu Dhabi, Aarhus Universitet
  • ,
  • Anthony Noll, Universite Toulouse III - Paul Sabatier
  • ,
  • Zeynep Çelik Orhan, Ege University
  • ,
  • Sibel Örtel, Ege University
  • ,
  • Ângela R.G. Santos, Space Science Institute
  • ,
  • Mutlu Yildiz, Ege University
  • ,
  • Sallie Baliunas, Harvard University
  • ,
  • Willie Soon, Harvard University

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.

OriginalsprogEngelsk
Artikelnummer154
TidsskriftAstrophysical Journal
Vol/bind900
Nummer2
Antal sider11
ISSN0004-637X
DOI
StatusUdgivet - sep. 2020

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