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Suppression of Quadrupole and Octupole Modes in Red Giants Observed by Kepler

Stello, Dennis and Cantiello, Matteo and Fuller, Jim and Garcia, Rafael A. and Huber, Daniel (2016) Suppression of Quadrupole and Octupole Modes in Red Giants Observed by Kepler. Publications of the Astronomical Society of Australia, 33 . Art. No. e011. ISSN 1323-3580. doi:10.1017/pasa.2016.9.

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An exciting new theoretical result shows that observing suppression of dipole oscillation modes in red giant stars can be used to detect strong magnetic fields in the stellar cores. A fundamental facet of the theory is that nearly all the mode energy leaking into the core is trapped by the magnetic greenhouse effect. This results in clear predictions for how the mode visibility changes as a star evolves up the red giant branch, and how that depends on stellar mass, spherical degree, and mode lifetime. Here, we investigate the validity of these predictions with a focus on the visibility of different spherical degrees. We find that mode suppression weakens for higher degree modes with a reduction in the quadrupole mode visibility of up to 49%, and no detectable suppression of octupole modes, in agreement with theory. We find evidence for the influence of increasing mode lifetimes on the visibilities along the red giant branch, in agreement with previous independent observations. These results support the theory that strong internal magnetic fields cause suppression of non-radial modes in red giants. We also find preliminary evidence that stars with suppressed dipole modes on average have slightly lower metallicity than normal stars.

Item Type:Article
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URLURL TypeDescription Paper
Cantiello, Matteo0000-0002-8171-8596
Fuller, Jim0000-0002-4544-0750
Huber, Daniel0000-0001-8832-4488
Additional Information:© 2016 Astronomical Society of Australia. Received January 19 2016; Accepted February 12 2016. We acknowledge the entire Kepler team, whose efforts made these results possible. D.S. is the recipient of an Australian Research Council Future Fellowship (project number FT140100147). J.F. acknowledges support from NSF under grant no. AST-1205732 and through a Lee DuBridge Fellowship at Caltech. R.A.G. acknowledge the support of the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 269194 (IRSES/ASK), the ANR- IDEE (n ANR-12-BS05-0008), and from the CNES. D.H. acknowledges support by the Australian Research Council’s Discovery Projects funding scheme (project number DE140101364) and support by the National Aeronautics and Space Administration under Grant NNX14AB92G issued through the Kepler Participating Scientist Program. This project was supported by NASA under TCAN grant number NNX14AB53G, and the NSF under grants PHY 11-25915 and AST 11-09174. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement no.: DNRF106). The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (Grant agreement no.: 267864).
Group:TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Australian Research CouncilFT140100147
Lee A. DuBridge FoundationUNSPECIFIED
European Research Council (ERC)269194
Agence Nationale pour la Recherche (ANR)ANR-12-BS05-0008
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Australian Research CouncilDE140101364
NSFPHY 11-25915
NSFAST 11-09174
Danish National Research FoundationDNRF106
European Research Council (ERC)267864 ASTERISK
Subject Keywords:stars: fundamental parameters — stars: oscillations — stars: interiors — stars: magnetic field
Record Number:CaltechAUTHORS:20160408-143954572
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Official Citation: Dennis Stello, Matteo Cantiello, Jim Fuller, Rafael A. Garcia and Daniel Huber (2016). Suppression of Quadrupole and Octupole Modes in Red Giants Observed by Kepler. Publications of the Astronomical Society of Australia, 33, e011 doi:10.1017/pasa.2016.9
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66033
Deposited By: Tony Diaz
Deposited On:12 Apr 2016 23:35
Last Modified:10 Nov 2021 23:52

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