[en] Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly ~50seconds) and those that are also burning helium (period spacing ~100 to 300 seconds).
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Bedding, Timothy R; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, New South Wales 2006, Australia
Mosser, Benoit; LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon cedex, France
Huber, Daniel; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, New South Wales 2006, Australia
Montalban Iglesias, Josefa ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Beck, Paul; Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
Christensen-Dalsgaard, Jørgen; Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Elsworth, Yvonne P; School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
García, Rafael A; Laboratoire AIM, CEA/DSM-CNRS, Université Paris 7 Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
Miglio, Andrea ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Stello, Dennis; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, New South Wales 2006, Australia
White, Timothy R; Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, New South Wales 2006, Australia
De Ridder, Joris; Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
Hekker, Saskia; School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
Aerts, Conny; Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
Barban, Caroline; LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon cedex, France
Belkacem, Kevin; Institut d'Astrophysique Spatiale, UMR 8617, Université Paris XI, Bâtiment 121, 91405 Orsay Cedex, France
Broomhall, Anne-Marie; School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
Brown, Timothy M.; Las Cumbres Observatory Global Telescope, Goleta, California 93117, USA
Buzasi, Derek L.; Eureka Scientific, 2452 Delmer Street Suite 100, Oakland, California 94602-3017, USA
Carrier, Fabien; Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
Chaplin, William J; School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
di Mauro, Maria Pia; INAF - IASF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
Dupret, Marc-Antoine ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Frandsen, Søren; Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Gilliland, Ronald L; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
Goupil, Marie-Jo; LESIA, CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon cedex, France
Jenkins, Jon M; SETI Institute/NASA Ames Research Center, MS 244-30, Moffett Field, California 94035, USA
Kallinger, Thomas; Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada
Kawaler, Steven; Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
Kjeldsen, Hans; Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
Mathur, Savita; High Altitude Observatory, NCAR, PO Box 3000, Boulder, Colorado 80307, USA
Noels-Grötsch, Arlette ; Institut d'Astrophysique et de Géophysique de l'Université de Liège, Allée du 6 Août 17, B 4000 Liège, Belgium
Aguirre, Victor Silva; Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching bei München, Germany
Ventura, Paolo; INAF - Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
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