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Title: Surface activity and oscillation amplitudes of red giants in eclipsing binaries

Among the 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection in the remaining 4 is an observational bias or possibly evidence of mode damping that originates from tidal interactions. A careful analysis of the corresponding Kepler light curves shows that modes with amplitudes that are usually observed in red giants would have been detected if they were present. We observe that mode depletion is strongly associated with short-period systems, in which stellar radii account for 16%-24% of the semi-major axis, and where red-giant surface activity is detected. We suggest that when the rotational and orbital periods synchronize in close binaries, the red-giant component is spun up, so that a dynamo mechanism starts and generates a magnetic field, leading to observable stellar activity. Pressure modes would then be damped as acoustic waves dissipate in these fields.
Authors:
;  [1] ;  [2] ;  [3]
  1. Department of Astronomy, New Mexico State University, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003-8001 (United States)
  2. Institut d'Astrophysique Spatiale, Université Paris-Sud 11 and CNRS (UMR 8617), Bâtiment 121, F-91405 Orsay cedex (France)
  3. LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, F-92195 Meudon cedex (France)
Publication Date:
OSTI Identifier:
22357211
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; DETECTION; ECLIPSE; MAGNETIC FIELDS; OSCILLATIONS; RED GIANT STARS; SOUND WAVES; STAR EVOLUTION; STELLAR ACTIVITY; SURFACES; VISIBLE RADIATION