Asteroseismology can reveal strong internal magnetic fields in red giant stars.
Internal stellar magnetic fields are inaccessible to direct observations, and little is known about their amplitude, geometry, and evolution. We demonstrate that strong magnetic fields in the cores of red giant stars can be identified with asteroseismology. The fields can manifest themselves via depressed dipole stellar oscillation modes, arising from a magnetic greenhouse effect that scatters and traps oscillation-mode energy within the core of the star. The Kepler satellite has observed a few dozen red giants with depressed dipole modes, which we interpret as stars with strongly magnetized cores. We find that field strengths larger than ~10(5) gauss may produce the observed depression, and in one case we infer a minimum core field strength of ≈10(7) gauss.
TAPIR, Walter Burke Institute for Theoretical Physics, Mailcode 350-17 California Institute of Technology, Pasadena, CA 91125, USA. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA. jfuller@caltech.edu matteo@kitp.ucsb.edu.
Jim
J
Fuller
Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA. jfuller@caltech.edu matteo@kitp.ucsb.edu.
Matteo
M
Cantiello
Sydney Institute for Astronomy, School of Physics, University of Sydney, New South Wales 2006, Australia. Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
Dennis
D
Stello
Laboratoire Astrophysique Interactions Multi-échelles, Commissariat á l'Énergie Atomique/Direction des Sciences de la Matiére, CNRS, Université Paris Diderot, Institut de Recherches sur les lois Fondamentales de l'Univers/Service d'Astrophysique Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France.
Rafael A
RA
Garcia
Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA. Department of Physics, University of California, Santa Barbara, CA 93106, USA.
Lars
L
Bildsten