Author: "S. Hekker" - Searchworks@Jio Institute Digital Library Search Results

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45 results on '"S. Hekker"'

1. Hot super-Earths stripped by their host stars

Author: M. S. Lundkvist, H. Kjeldsen, S. Albrecht, G. R. Davies, S. Basu, D. Huber, A. B. Justesen, C. Karoff, V. Silva Aguirre, V. Van Eylen, C. Vang, T. Arentoft, T. Barclay, T. R. Bedding, T. L. Campante, W. J. Chaplin, J. Christensen-Dalsgaard, Y. P. Elsworth, R. L. Gilliland, R. Handberg, S. Hekker, S. D. Kawaler, M. N. Lund, T. S. Metcalfe, A. Miglio, J. F. Rowe, D. Stello, B. Tingley, and T. R. White
Subjects: Science
Abstract: Theory predicts a deficit of super-Earth sized planets, which orbit close to their host star. Here, Lundkvist et al. use data from the NASA Kepler mission to show that this deficit is also seen in observations, thereby providing new insight into exoplanetary systems.
Published: 2016
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2. Mirror principle and the red-giant bump: the battle of entropy in low-mass stars

Author: S Hekker, G C Angelou, Y Elsworth, and S Basu
Published: 2020
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3. PLATO as it is: A legacy mission for Galactic archaeology

Author: A. Miglio, C. Chiappini, B. Mosser, G. R. Davies, K. Freeman, L. Girardi, P. Jofré, D. Kawata, B. M. Rendle, M. Valentini, L. Casagrande, W. J. Chaplin, G. Gilmore, K. Hawkins, B. Holl, T. Appourchaux, K. Belkacem, D. Bossini, K. Brogaard, M.‐J. Goupil, J. Montalbán, A. Noels, F. Anders, T. Rodrigues, G. Piotto, D. Pollacco, H. Rauer, C. Allende Prieto, P. P. Avelino, C. Babusiaux, C. Barban, B. Barbuy, S. Basu, F. Baudin, O. Benomar, O. Bienaymé, J. Binney, J. Bland‐Hawthorn, A. Bressan, C. Cacciari, T. L. Campante, S. Cassisi, J. Christensen‐Dalsgaard, F. Combes, O. Creevey, M. S. Cunha, R. S. Jong, P. Laverny, S. Degl'Innocenti, S. Deheuvels, É. Depagne, J. Ridder, P. Di Matteo, M. P. Di Mauro, M.‐A. Dupret, P. Eggenberger, Y. Elsworth, B. Famaey, S. Feltzing, R. A. García, O. Gerhard, B. K. Gibson, L. Gizon, M. Haywood, R. Handberg, U. Heiter, S. Hekker, D. Huber, R. Ibata, D. Katz, S. D. Kawaler, H. Kjeldsen, D. W. Kurtz, N. Lagarde, Y. Lebreton, M. N. Lund, S. R. Majewski, P. Marigo, M. Martig, S. Mathur, I. Minchev, T. Morel, S. Ortolani, M. H. Pinsonneault, B. Plez, P. G. Prada Moroni, D. Pricopi, A. Recio‐Blanco, C. Reylé, A. Robin, I. W. Roxburgh, M. Salaris, B. X. Santiago, R. Schiavon, A. Serenelli, S. Sharma, V. Silva Aguirre, C. Soubiran, M. Steinmetz, D. Stello, K. G. Strassmeier, P. Ventura, R. Ventura, N. A. Walton, and C. C. Worley
Published: 2017
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4. Asteroseismology of luminous red giants with Kepler - II

Author: Timothy R. Bedding, Daniel Huber, Jie Yu, Shourya Khanna, Dennis Stello, Shaolan Bi, S. Hekker, Laurent Gizon, and Astronomy
Subjects: oscillations [stars], Infrared, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, Luminosity, photometric [techniques], techniques: photometric, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, stars: late-type, Astronomy and Astrophysics, mass-loss [stars], Mass ratio, Astrophysics - Astrophysics of Galaxies, Red-giant branch, Interstellar medium, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), late-type [stars], Astrophysics::Earth and Planetary Astrophysics, stars: oscillations, stars: mass-loss
Abstract: Mass loss by red giants is an important process to understand the final stages of stellar evolution and the chemical enrichment of the interstellar medium. Mass-loss rates are thought to be controlled by pulsation-enhanced dust-driven outflows. Here we investigate the relationships between mass loss, pulsations, and radiation, using 3213 luminous Kepler red giants and 135000 ASAS-SN semiregulars and Miras. Mass-loss rates are traced by infrared colours using 2MASS and WISE and by observed-to-model WISE fluxes, and are also estimated using dust mass-loss rates from literature assuming a typical gas-to-dust mass ratio of 400. To specify the pulsations, we extract the period and height of the highest peak in the power spectrum of oscillation. Absolute magnitudes are obtained from the 2MASS Ks band and the Gaia DR2 parallaxes. Our results follow. (i) Substantial mass loss sets in at pulsation periods above ~60 and ~100 days, corresponding to Asymptotic-Giant-Branch stars at the base of the period-luminosity sequences C' and C. (ii) The mass-loss rate starts to rapidly increase in semiregulars for which the luminosity is just above the Red-Giant-Branch tip and gradually plateaus to a level similar to that of Miras. (iii) The mass-loss rates in Miras do not depend on luminosity, consistent with pulsation-enhanced dust-driven winds. (iv) The accumulated mass loss on the Red Giant Branch consistent with asteroseismic predictions reduces the masses of red-clump stars by 6.3%, less than the typical uncertainty on their asteroseismic masses. Thus mass loss is currently not a limitation of stellar age estimates for galactic archaeology studies., 14 pages, 12 figures, accepted for publication in MNRAS
Published: 2021

5. The 16th Data Release of the Sloan Digital Sky Surveys : First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra

Author: Romina Ahumada, Carlos Allende Prieto, Andrés Almeida, Friedrich Anders, Scott F. Anderson, Brett H. Andrews, Borja Anguiano, Riccardo Arcodia, Eric Armengaud, Marie Aubert, Santiago Avila, Vladimir Avila-Reese, Carles Badenes, Christophe Balland, Kat Barger, Jorge K. Barrera-Ballesteros, Sarbani Basu, Julian Bautista, Rachael L. Beaton, Timothy C. Beers, B. Izamar T. Benavides, Chad F. Bender, Mariangela Bernardi, Matthew Bershady, Florian Beutler, Christian Moni Bidin, Jonathan Bird, Dmitry Bizyaev, Guillermo A. Blanc, Michael R. Blanton, Médéric Boquien, Jura Borissova, Jo Bovy, W. N. Brandt, Jonathan Brinkmann, Joel R. Brownstein, Kevin Bundy, Martin Bureau, Adam Burgasser, Etienne Burtin, Mariana Cano-Díaz, Raffaella Capasso, Michele Cappellari, Ricardo Carrera, Solène Chabanier, William Chaplin, Michael Chapman, Brian Cherinka, Cristina Chiappini, Peter Doohyun Choi, S. Drew Chojnowski, Haeun Chung, Nicolas Clerc, Damien Coffey, Julia M. Comerford, Johan Comparat, Luiz da Costa, Marie-Claude Cousinou, Kevin Covey, Jeffrey D. Crane, Katia Cunha, Gabriele da Silva Ilha, Yu Sophia Dai, Sanna B. Damsted, Jeremy Darling, James W. Davidson, Roger Davies, Kyle Dawson, Nikhil De, Axel de la Macorra, Nathan De Lee, Anna Bárbara de Andrade Queiroz, Alice Deconto Machado, Sylvain de la Torre, Flavia Dell’Agli, Hélion du Mas des Bourboux, Aleksandar M. Diamond-Stanic, Sean Dillon, John Donor, Niv Drory, Chris Duckworth, Tom Dwelly, Garrett Ebelke, Sarah Eftekharzadeh, Arthur Davis Eigenbrot, Yvonne P. Elsworth, Mike Eracleous, Ghazaleh Erfanianfar, Stephanie Escoffier, Xiaohui Fan, Emily Farr, José G. Fernández-Trincado, Diane Feuillet, Alexis Finoguenov, Patricia Fofie, Amelia Fraser-McKelvie, Peter M. Frinchaboy, Sebastien Fromenteau, Hai Fu, Lluís Galbany, Rafael A. Garcia, D. A. García-Hernández, Luis Alberto Garma Oehmichen, Junqiang Ge, Marcio Antonio Geimba Maia, Doug Geisler, Joseph Gelfand, Julian Goddy, Violeta Gonzalez-Perez, Kathleen Grabowski, Paul Green, Catherine J. Grier, Hong Guo, Julien Guy, Paul Harding, Sten Hasselquist, Adam James Hawken, Christian R. Hayes, Fred Hearty, S. Hekker, David W. Hogg, Jon A. Holtzman, Danny Horta, Jiamin Hou, Bau-Ching Hsieh, Daniel Huber, Jason A. S. Hunt, J. Ider Chitham, Julie Imig, Mariana Jaber, Camilo Eduardo Jimenez Angel, Jennifer A. Johnson, Amy M. Jones, Henrik Jönsson, Eric Jullo, Yerim Kim, Karen Kinemuchi, Charles C. Kirkpatrick IV, George W. Kite, Mark Klaene, Jean-Paul Kneib, Juna A. Kollmeier, Hui Kong, Marina Kounkel, Dhanesh Krishnarao, Ivan Lacerna, Ting-Wen Lan, Richard R. Lane, David R. Law, Jean-Marc Le Goff, Henry W. Leung, Hannah Lewis, Cheng Li, Jianhui Lian, Lihwai Lin, Dan Long, Penélope Longa-Peña, Britt Lundgren, Brad W. Lyke, J. Ted Mackereth, Chelsea L. MacLeod, Steven R. Majewski, Arturo Manchado, Claudia Maraston, Paul Martini, Thomas Masseron, Karen L. Masters, Savita Mathur, Richard M. McDermid, Andrea Merloni, Michael Merrifield, Szabolcs Mészáros, Andrea Miglio, Dante Minniti, Rebecca Minsley, Takamitsu Miyaji, Faizan Gohar Mohammad, Benoit Mosser, Eva-Maria Mueller, Demitri Muna, Andrea Muñoz-Gutiérrez, Adam D. Myers, Seshadri Nadathur, Preethi Nair, Kirpal Nandra, Janaina Correa do Nascimento, Rebecca Jean Nevin, Jeffrey A. Newman, David L. Nidever, Christian Nitschelm, Pasquier Noterdaeme, Julia E. O’Connell, Matthew D. Olmstead, Daniel Oravetz, Audrey Oravetz, Yeisson Osorio, Zachary J. Pace, Nelson Padilla, Nathalie Palanque-Delabrouille, Pedro A. Palicio, Hsi-An Pan, Kaike Pan, James Parker, Romain Paviot, Sebastien Peirani, Karla Peña Ramŕez, Samantha Penny, Will J. Percival, Ismael Perez-Fournon, Ignasi Pérez-Ràfols, Patrick Petitjean, Matthew M. Pieri, Marc Pinsonneault, Vijith Jacob Poovelil, Joshua Tyler Povick, Abhishek Prakash, Adrian M. Price-Whelan, M. Jordan Raddick, Anand Raichoor, Amy Ray, Sandro Barboza Rembold, Mehdi Rezaie, Rogemar A. Riffel, Rogério Riffel, Hans-Walter Rix, Annie C. Robin, A. Roman-Lopes, Carlos Román-Zúñiga, Benjamin Rose, Ashley J. Ross, Graziano Rossi, Kate Rowlands, Kate H. R. Rubin, Mara Salvato, Ariel G. Sánchez, Laura Sánchez-Menguiano, José R. Sánchez-Gallego, Conor Sayres, Adam Schaefer, Ricardo P. Schiavon, Jaderson S. Schimoia, Edward Schlafly, David Schlegel, Donald P. Schneider, Mathias Schultheis, Axel Schwope, Hee-Jong Seo, Aldo Serenelli, Arman Shafieloo, Shoaib Jamal Shamsi, Zhengyi Shao, Shiyin Shen, Matthew Shetrone, Raphael Shirley, Víctor Silva Aguirre, Joshua D. Simon, M. F. Skrutskie, Anže Slosar, Rebecca Smethurst, Jennifer Sobeck, Bernardo Cervantes Sodi, Diogo Souto, David V. Stark, Keivan G. Stassun, Matthias Steinmetz, Dennis Stello, Julianna Stermer, Thaisa Storchi-Bergmann, Alina Streblyanska, Guy S. Stringfellow, Amelia Stutz, Genaro Suárez, Jing Sun, Manuchehr Taghizadeh-Popp, Michael S. Talbot, Jamie Tayar, Aniruddha R. Thakar, Riley Theriault, Daniel Thomas, Zak C. Thomas, Jeremy Tinker, Rita Tojeiro, Hector Hernandez Toledo, Christy A. Tremonti, Nicholas W. Troup, Sarah Tuttle, Eduardo Unda-Sanzana, Marica Valentini, Jaime Vargas-González, Mariana Vargas-Magaña, Jose Antonio Vázquez-Mata, M. Vivek, David Wake, Yuting Wang, Benjamin Alan Weaver, Anne-Marie Weijmans, Vivienne Wild, John C. Wilson, Robert F. Wilson, Nathan Wolthuis, W. M. Wood-Vasey, Renbin Yan, Meng Yang, Christophe Yèche, Olga Zamora, Pauline Zarrouk, Gail Zasowski, Kai Zhang, Cheng Zhao, Gongbo Zhao, Zheng Zheng, Guangtun Zhu, Hu Zou, Department of Physics, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Instituto de Astrofisica de Canarias (IAC), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Universidad Nacional Autónoma de México (UNAM), Department of Astrophysical Sciences [Princeton], Princeton University, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Department of Astronomy, Yale University [New Haven], University of Notre Dame [Indiana] (UND), Department of Physics and Astronomy [Philadelphia], University of Pennsylvania [Philadelphia], University of Wisconsin-Madison, Texas Tech University Health Sciences Center, Texas Tech University [Lubbock] (TTU), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), California Institute of Technology (CALTECH), Sub-department of Astrophysics [Oxford], Department of Physics [Oxford], University of Oxford [Oxford]-University of Oxford [Oxford], Center for Astrophysics and Space Sciences [La Jolla] (CASS), University of California [San Diego] (UC San Diego), University of California-University of California, Department of Psychology, St John's University, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Departamento de FisicaTeorica e IFT-UAM/CSIC, Universidad Autonoma de Madrid (UAM), Lowell Observatory [Flagstaff], Observatorio Nacional [Rio de Janeiro], Vernalis (R&D) Ltd, Special Care Dentistry, UCLH Eastman Dental Hospital, University of Utah, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Universidad de La Laguna [Tenerife - SP] (ULL), University of Virginia [Charlottesville], University of Wyoming (UW), School of Physics and Astronomy, University of Birmingham [Birmingham], Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Arizona State University [Tempe] (ASU), Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Max-Planck-Institut für Astronomie (MPIA), Texas Christian University (TCU), Department of Physics and Astronomy [Irvine], University of California [Irvine] (UCI), Department of Physics and Astronomy [Pittsburgh], University of Pittsburgh (PITT), Pennsylvania Commonwealth System of Higher Education (PCSHE)-Pennsylvania Commonwealth System of Higher Education (PCSHE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), New York University [New York] (NYU), NYU System (NYU), Research Institute of Forest Resource Information Techniques, Chinese Academy of Forestry, New Mexico State University, Pennsylvania State University (Penn State), Penn State System, Princess Margaret Hospital, University of Toronto, Cognition, Langues, Langage, Ergonomie (CLLE-ERSS), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Toulouse - Jean Jaurès (UT2J)-Université Bordeaux Montaigne-Centre National de la Recherche Scientifique (CNRS), J. A. Baker Institute, Cornell University [New York], Institute of Infection, Immunity & Inflammation, University of Glasgow, Sainsbury Laboratory Cambridge University (SLCU), University of Cambridge [UK] (CAM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Carnegie Observatories, Carnegie Institution for Science [Washington], Institute of Science and Technology [Austria] (IST Austria), Universidad de Atacama, Department of Chemical and Biomolecular Engineering, Universidad de Antofagasta, Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Institute of cosmology and gravitation, University of Portsmouth, Institut d'Astronomie et d'Astrophysique [Bruxelles] (IAA), Université libre de Bruxelles (ULB), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Max-Planck-Institut für Astrophysik (MPA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, Universidad Andrés Bello [Santiago] (UNAB), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Montana State University (MSU), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Institut Lagrange de Paris, Sorbonne Université (SU), The Wellcome Trust Centre for Human Genetics [Oxford], University of Oxford [Oxford], Liverpool John Moores University (LJMU), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Space Sciences [Barcelona] (ICE-CSIC), Spanish National Research Council [Madrid] (CSIC), Chinese Academy of Sciences [Beijing] (CAS), McDonald Observatory, University of Texas at Austin [Austin], Astronomy Centre, University of Sussex, Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], University of Washington [Seattle], Vanderbilt University [Nashville], Stellar Astrophysics Centre [Aarhus] (SAC), University of Colorado [Boulder], Laboratoire de Biochimie Médicale (LBM), CHU Rouen, Normandie Université (NU)-Normandie Université (NU), University of St Andrews [Scotland], Instituto de Astronomıa, universidad catolica del Norte, Institut d'Astrophysique et de Géophysique [Liège], Laboratoire de Physique des Solides (LPS), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Department of Computer Science and Engineering [Minneapolis], University of Minnesota [Twin Cities] (UMN), University of Minnesota System-University of Minnesota System, Dunlap Institute for Astronomy and Astrophysics [Toronto], World Bank, State Key Laboratory in Computer Science [Beijing] (SKLCS), Institute of Software Chinese Academy of Sciences [Beijing], Nanjing University of Information Science and Technology (NUIST), Laboratoire de Chimie - UMR5182 (LC), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon)-Institut de Chimie du CNRS (INC), Johns Hopkins University (JHU), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of Pennsylvania, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Oxford-University of Oxford, University of California (UC)-University of California (UC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Universidad Autónoma de Madrid (UAM), University of Virginia, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), University of California [Irvine] (UC Irvine), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS), Carnegie Institution for Science, Institute of Science and Technology [Klosterneuburg, Austria] (IST Austria), Harvard University-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Oxford, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Ahumada R., Prieto C.A., Almeida A., Anders F., Anderson S.F., Andrews B.H., Anguiano B., Arcodia R., Armengaud E., Aubert M., Avila S., Avila-Reese V., Badenes C., Balland C., Barger K., Barrera-Ballesteros J.K., Basu S., Bautista J., Beaton R.L., Beers T.C., Benavides B.I.T., Bender C.F., Bernardi M., Bershady M., Beutler F., Bidin C.M., Bird J., Bizyaev D., Blanc G.A., Blanton M.R., Boquien M., Borissova J., Bovy J., Brandt W.N., Brinkmann J., Brownstein J.R., Bundy K., Bureau M., Burgasser A., Burtin E., Cano-Diaz M., Capasso R., Cappellari M., Carrera R., Chabanier S., Chaplin W., Chapman M., Cherinka B., Chiappini C., Doohyun Choi P., Chojnowski S.D., Chung H., Clerc N., Coffey D., Comerford J.M., Comparat J., Da Costa L., Cousinou M.-C., Covey K., Crane J.D., Cunha K., Ilha G.D.S., Dai Y.S., Damsted S.B., Darling J., Davidson J.W., Davies R., Dawson K., De N., De La Macorra A., De Lee N., Queiroz A.B.D.A., Deconto Machado A., De La Torre S., Dell'Agli F., Du Mas Des Bourboux H., Diamond-Stanic A.M., Dillon S., Donor J., Drory N., Duckworth C., Dwelly T., Ebelke G., Eftekharzadeh S., Davis Eigenbrot A., Elsworth Y.P., Eracleous M., Erfanianfar G., Escoffier S., Fan X., Farr E., Fernandez-Trincado J.G., Feuillet D., Finoguenov A., Fofie P., Fraser-Mckelvie A., Frinchaboy P.M., Fromenteau S., Fu H., Galbany L., Garcia R.A., Garcia-Hernandez D.A., Oehmichen L.A.G., Ge J., Maia M.A.G., Geisler D., Gelfand J., Goddy J., Gonzalez-Perez V., Grabowski K., Green P., Grier C.J., Guo H., Guy J., Harding P., Hasselquist S., Hawken A.J., Hayes C.R., Hearty F., Hekker S., Hogg D.W., Holtzman J.A., Horta D., Hou J., Hsieh B.-C., Huber D., Hunt J.A.S., Chitham J.I., Imig J., Jaber M., Angel C.E.J., Johnson J.A., Jones A.M., Jonsson H., Jullo E., Kim Y., Kinemuchi K., Kirkpatrick Iv C.C., Kite G.W., Klaene M., Kneib J.-P., Kollmeier J.A., Kong H., Kounkel M., Krishnarao D., Lacerna I., Lan T.-W., Lane R.R., Law D.R., Le Goff J.-M., Leung H.W., Lewis H., Li C., Lian J., Lin L., Long D., Longa-Peña P., Lundgren B., Lyke B.W., Ted Mackereth J., Macleod C.L., Majewski S.R., Manchado A., Maraston C., Martini P., Masseron T., Masters K.L., Mathur S., McDermid R.M., Merloni A., Merrifield M., Meszaros S., Miglio A., Minniti D., Minsley R., Miyaji T., Mohammad F.G., Mosser B., Mueller E.-M., Muna D., Muñoz-Gutierrez A., Myers A.D., Nadathur S., Nair P., Nandra K., Do Nascimento J.C., Nevin R.J., Newman J.A., Nidever D.L., Nitschelm C., Noterdaeme P., O'Connell J.E., Olmstead M.D., Oravetz D., Oravetz A., Osorio Y., Pace Z.J., Padilla N., Palanque-Delabrouille N., Palicio P.A., Pan H.-A., Pan K., Parker J., Paviot R., Peirani S., Ramrez K.P., Penny S., Percival W.J., Perez-Fournon I., Perez-Rafols I., Petitjean P., Pieri M.M., Pinsonneault M., Poovelil V.J., Povick J.T., Prakash A., Price-Whelan A.M., Raddick M.J., Raichoor A., Ray A., Rembold S.B., Rezaie M., Riffel R.A., Riffel R., Rix H.-W., Robin A.C., Roman-Lopes A., Roman-Zuñiga C., Rose B., Ross A.J., Rossi G., Rowlands K., Rubin K.H.R., Salvato M., Sanchez A.G., Sanchez-Menguiano L., Sanchez-Gallego J.R., Sayres C., Schaefer A., Schiavon R.P., Schimoia J.S., Schlafly E., Schlegel D., Schneider D.P., Schultheis M., Schwope A., Seo H.-J., Serenelli A., Shafieloo A., Shamsi S.J., Shao Z., Shen S., Shetrone M., Shirley R., Aguirre V.S., Simon J.D., Skrutskie M.F., Slosar A., Smethurst R., Sobeck J., Sodi B.C., Souto D., Stark D.V., Stassun K.G., Steinmetz M., Stello D., Stermer J., Storchi-Bergmann T., Streblyanska A., Stringfellow G.S., Stutz A., Suarez G., Sun J., Taghizadeh-Popp M., Talbot M.S., Tayar J., Thakar A.R., Theriault R., Thomas D., Thomas Z.C., Tinker J., Tojeiro R., Toledo H.H., Tremonti C.A., Troup N.W., Tuttle S., Unda-Sanzana E., Valentini M., Vargas-Gonzalez J., Vargas-Magaña M., Vazquez-Mata J.A., Vivek M., Wake D., Wang Y., Weaver B.A., Weijmans A.-M., Wild V., Wilson J.C., Wilson R.F., Wolthuis N., Wood-Vasey W.M., Yan R., Yang M., Yeche C., Zamora O., Zarrouk P., Zasowski G., Zhang K., Zhao C., Zhao G., Zheng Z., Zhu G., Zou H., Alfred P. Sloan Foundation, and Department of Energy (US)
Subjects: Optical telescopes, SAMPLE, Astrophysics, 01 natural sciences, Astronomi, astrofysik och kosmologi, Infrared astronomy, Observatory, Astronomy, Astrophysics and Cosmology, Astrophysics::Solar and Stellar Astrophysics, REDSHIFT 0.8, redshift surveys, stellar spectral lines, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, media_common, Astronomy databases, Redshift surveys, Physics, Astrophysics::Instrumentation and Methods for Astrophysics, stellar properties, CATALOG, astro-ph.CO, astronomy databases, Data release, [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], infrared astonomy, TELESCOPE, astro-ph.GA, media_common.quotation_subject, Astrophysics::Cosmology and Extragalactic Astrophysics, MASS, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Galactic abundances, Stellar properties, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, DISTANCES, Stellar spectral lines, 010308 nuclear & particles physics, Astronomy and Astrophysics, optical telescopes, 115 Astronomy, Space science, Galaxy, GALAXY, [PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], STELLAR, 13. Climate action, Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], galactic abundances, MILKY, astro-ph.IM, SDSS-IV MANGA
Abstract: This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)., Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS website is www.sdss.org.
Published: 2020

6. The Aarhus red giants challenge

Author: J. Christensen-Dalsgaard, V. Silva Aguirre, S. Cassisi, M. Miller Bertolami, A. Serenelli, D. Stello, A. Weiss, G. Angelou, C. Jiang, Y. Lebreton, F. Spada, E. P. Bellinger, S. Deheuvels, R. M. Ouazzani, A. Pietrinferni, J. R. Mosumgaard, R. H. D. Townsend, T. Battich, D. Bossini, T. Constantino, P. Eggenberger, S. Hekker, A. Mazumdar, A. Miglio, K. B. Nielsen, M. Salaris
Published: 2020
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7. TOI-257b (HD 19916b): A Warm sub-Saturn Orbiting an Evolved F-type Star

Author: Andrés Jordán, Derek Buzasi, K. I. Collins, Joshua Pepper, Jon M. Jenkins, Alexander Lyttle, Martin Schlecker, Ismael Mireles, Sara Seager, Brett C. Addison, Andrea Miglio, Jack Okumura, Savita Mathur, Christopher Tylor, Daniel R. Hey, Victor Silva Aguirre, Zhao Guo, Tansu Daylan, Paula Sarkis, Mikkel N. Lund, J. S. Bentley, Martin Bo Nielsen, Joshua E. Schlieder, Keivan G. Stassun, Aldo Serenelli, Jonathan Horner, Stephen R. Kane, Tiago L. Campante, B. D. Carter, Joshua N. Winn, Hui Zhang, Diana Kossakowski, Thomas Henning, Brendan P. Bowler, Rasmus Handberg, Jake T. Clark, Warrick H. Ball, Matthew W. Mengel, Pamela Rowden, L. González-Cuesta, Karen A. Collins, Andrew W. Mann, Nicholas M. Law, John F. Kielkopf, B. Mosser, Daniel Huber, Ian J. M. Crossfield, Mathieu Clerte, Michaela Collins, Ashley Chontos, Songhu Wang, Belinda A. Nicholson, Pascal Torres, Thomas Kallinger, Robert A. Wittenmyer, Stephen C. Marsden, Andrew Vanderburg, Dag Evensberget, N. Themeßl, Rachel A. Matson, José Dias do Nascimento, David W. Latham, Cenk Kayhan, Timothy R. Bedding, Allen B. Davis, Emilie Laychock, J. O'Connor, Néstor Espinoza, B. Cale, Andrius Burnelis, S. Hekker, Steven D. Kawaler, Avi Shporer, Duncan J. Wright, Sarbani Basu, Peter Plavchan, James S. Kuszlewicz, Guy R. Davies, Teo Mocnik, Leandro de Almeida, Jason D. Eastman, Carl Ziegler, Rafael Brahm, Enrico Corsaro, William J. Chaplin, C. G. Tinney, Catherine Stevens, Rafael A. García, Sergi Blanco-Cuaresma, Steve B. Howell, Alexis Heitzmann, Roland Vanderspek, Thiam-Guan Tan, George R. Ricker, Addison, Brett C, Wright, Duncan J, Nicholson, Belinda A, Cale, Bryson, Mocnik, Teo, Huber, Daniel, Plavchan, Peter, Wittenmyer, Robert A, Vanderburg, Andrew, Chaplin, William J, Chontos, Ashley, Clark, Jake T, Eastman, Jason D, Ziegler, Carl, Brahm, Rafael, Carter, Bradley D, Clerte, Mathieu, Espinoza, Néstor, Horner, Jonathan, Bentley, John, Jordán, André, Kane, Stephen R, Kielkopf, John F, Laychock, Emilie, Mengel, Matthew W, Okumura, Jack, Stassun, Keivan G, Bedding, Timothy R, Bowler, Brendan P, Burnelis, Andriu, Blanco-Cuaresma, Sergi, Collins, Michaela, Crossfield, Ian, Davis, Allen B, Evensberget, Dag, Heitzmann, Alexi, Howell, Steve B, Law, Nichola, Mann, Andrew W, Marsden, Stephen C, Matson, Rachel A, O’Connor, James H, Shporer, Avi, Stevens, Catherine, Tinney, C G, Tylor, Christopher, Wang, Songhu, Zhang, Hui, Henning, Thoma, Kossakowski, Diana, Ricker, George, Sarkis, Paula, Schlecker, Martin, Torres, Pascal, Vanderspek, Roland, Latham, David W, Seager, Sara, Winn, Joshua N, Jenkins, Jon M, Mireles, Ismael, Rowden, Pam, Pepper, Joshua, Daylan, Tansu, Schlieder, Joshua E, Collins, Karen A, Collins, Kevin I, Tan, Thiam-Guan, Ball, Warrick H, Basu, Sarbani, Buzasi, Derek L, Campante, Tiago L, Corsaro, Enrico, González-Cuesta, L, Davies, Guy R, de Almeida, Leandro, do Nascimento, Jose-Dia, García, Rafael A, Guo, Zhao, Handberg, Rasmu, Hekker, Saskia, Hey, Daniel R, Kallinger, Thoma, Kawaler, Steven D, Kayhan, Cenk, S. Kuszlewicz, Jame, Lund, Mikkel N, Lyttle, Alexander, Mathur, Savita, Miglio, Andrea, Mosser, Benoit, Nielsen, Martin B, Serenelli, Aldo M, Aguirre, Victor Silva, Themeßl, Nathalie, National Aeronautics and Space Administration (US), National Science Foundation (US), Danish National Research Foundation, National Natural Science Foundation of China, Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, European Commission, Centre National D'Etudes Spatiales (France), Ministerio de Economía y Competitividad (España), Kavli Institute for Theoretical Physics, Independent Research Fund Denmark, Carlsberg Foundation, Addison, Brett C., Wright, Duncan J., Nicholson, Belinda A., Wittenmyer, Robert A., Chaplin, William J., Clark, Jake T., Eastman, Jason D., Carter, Bradley D., Kane, Stephen R., Kielkopf, John F., Mengel, Matthew W., Stassun, Keivan G., Bedding, Timothy R., Bowler, Brendan P., Davis, Allen B., Howell, Steve B., Mann, Andrew W., Marsden, Stephen C., Matson, Rachel A., O'Connor, Jame, Tinney, C. G., Latham, David W., Winn, Joshua N., Jenkins, Jon M., Schlieder, Joshua E., Collins, Karen A., Collins, Kevin I., Ball, Warrick H., Buzasi, Derek L., Campante, Tiago L., González-Cuesta, Lucía, Davies, Guy R., do Nascimento, Jose-Dias, Jr., García, Rafael A., Hey, Daniel R., Kawaler, Steven D., Kuszlewicz, James S., Lund, Mikkel N., Nielsen, Martin B., Serenelli, Aldo M., and Silva Aguirre, Victor
Subjects: astro-ph.SR, Star (game theory), FOS: Physical sciences, Context (language use), Astrophysics, asteroseismology, Type (model theory), 01 natural sciences, Asteroseismology, spectroscopic [Techniques], techniques: photometric, stars: individual (TIC 200723869/TOI-257), 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, Earth and Planetary Astrophysics (astro-ph.EP), individual (TIC 200723869/TOI-257) [Stars], radial velocities [Techniques], 010308 nuclear & particles physics, photometric [Techniques], techniques: radial velocitie, Astronomy and Astrophysics, Planetary system, planetary system, Exoplanet, Radial velocity, Stars, Planetary systems, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Techniques: radial velocities, astro-ph.EP, techniques: spectroscopic, Astrophysics - Earth and Planetary Astrophysics
Abstract: We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the Minerva-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 M J (43.9 ± 7.3, M⊕), a radius of RP = 0.639 ± 0.013 R J (7.16 ± 0.15, R ⊕), bulk density of 0.65+0.12-0.11 (cgs), and period 18.38818 +0.00085 -0.00084 days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M∗ = 1.390 ± 0.046 rm M sun, R∗ = 1.888 ± 0.033 Rsun, Teff = 6075 ± 90 rm K, and vsin i = 11.3 ± 0.5 km s-1. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems., Daniel Huber acknowledges support by the National Aeronautics and Space Administration through the TESS Guest Investigator Program (80NSSC18K1585) and by the National Science Foundation (AST-1717000). Ashley Chontos acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program (DGE 1842402). William J. Chaplin, Warrick H. Ball, Martin B. Nielsen, and Andrea Miglio. acknowledge support from the Science and Technology Facilities Council and UK Space Agency. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). Rafael Brahm acknowledges support from National Fund for Scientific and Technological Development Post-doctoral Fellowship Project 3180246, and from the Millennium Institute of Astrophysics (MAS). H.Z. Hui Zhang is supported by the Natural Science Foundation of China (NSFC grants 11673011, 11933001). Andres Jordan acknowledges support from FONDECYT project 1171208 and by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS). Aldo M. Serenelli is partially supported by grants ESP2017-82674-R (Spanish Government) and 2017-SGR-1131 (Generalitat de Catalunya). Andrea Miglio acknowledges support from the European Research Council Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, G.A. number 772293). Rafael A. Garcia acknowledges the support of the PLAnetary Transits and Oscillations of stars grant from the Centre National d'Études Spatiales. Savita Mathur acknowledges support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. Tiago L. Campante acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 792848 (PULSATION). This work was supported by Foundation of Science and Technology/Ministry of Science, Technology and Higher Education through national funds (UID/FIS/04434/2019). Enrico Corsaro is funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 664931. L. González-Cuesta thanks the support from grant FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO) (research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610). Sarbani Basu acknowledges NASA grant NNX16AI09G and NSF grant AST-1514676. Ian J. M. Crossfield acknowledges support from the NSF through grant AST-1824644, and from NASA through Caltech/JPL grant RSA-1610091. Tansu Daylan acknowledges support from MIT’s Kavli Institute as a Kavli postdoctoral fellow. Derek L. Buzasi acknowledges support from NASA through the TESS Guest Investigator program (80NSSC19K0385). Cenk Kayhan acknowledges support by Erciyes University Scientific Research Projects Coordination Unit under grant number MAP-2020-9749. Emilie Laychock and Michaela Collins acknowledge support by the National Science Foundation under grant 1559487. Victor Silva Aguirre acknowledges support from the Independent Research Fund Denmark (Research grant 7027-00096B) and the Carlsberg Foundation (grant agreement CF19-0649).
Published: 2020
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8. Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets★†

Author: J. Molenda-Zakowicz, Clara Régulo, T. Appourchaux, T. L. Campante, C. Catala, K. Uytterhoeven, D. T. Sanderfer, Robert L. Morris, Ian W. Roxburgh, Rasmus Handberg, H. Kjeldsen, Daniel Huber, H. Bruntt, A. O. Thygesen, Barry Smalley, S. Basu, T. R. Bedding, Yvonne Elsworth, Elisa V. Quintana, William J. Chaplin, B. Mosser, J.-C. Gazzano, D. Stello, P.-O. Quirion, R. A. Garcia, Graham A. Verner, J. Christensen-Dalsgaard, S. Mathur, T. S. Metcalfe, S. D. Kawaler, S. Hekker, and Christoffer Karoff
Subjects: Physics, 010308 nuclear & particles physics, Metallicity, Astronomy and Astrophysics, Astrophysics, Surface gravity, Light curve, 01 natural sciences, Kepler, Stars, Space and Planetary Science, 0103 physical sciences, Magnitude (astronomy), Calibration, 010303 astronomy & astrophysics, Scaling
Abstract: We present a detailed spectroscopic study of 93 solar-type stars that are targets of the NASA/Kepler mission and provide detailed chemical composition of each target. We find that the overall metallicity is well-represented by Fe lines. Relative abundances of light elements (CNO) and alpha-elements are generally higher for low-metallicity stars. Our spectroscopic analysis benefits from the accurately measured surface gravity from the asteroseismic analysis of the Kepler light curves. The log g parameter is known to better than 0.03 dex and is held fixed in the analysis. We compare our Teff determination with a recent colour calibration of V-K (TYCHO V magnitude minus 2MASS Ks magnitude) and find very good agreement and a scatter of only 80 K, showing that for other nearby Kepler targets this index can be used. The asteroseismic log g values agree very well with the classical determination using Fe1-Fe2 balance, although we find a small systematic offset of 0.08 dex (asteroseismic log g values are lower). The abundance patterns of metals, alpha elements, and the light elements (CNO) show that a simple scaling by [Fe/H] is adequate to represent the metallicity of the stars, except for the stars with metallicity below -0.3, where alpha-enhancement becomes important. However, this is only important for a very small fraction of the Kepler sample. We therefore recommend that a simple scaling with [Fe/H] be employed in the asteroseismic analyses of large ensembles of solar-type stars.
Published: 2012

9. Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819

Author: Arlette Noels, B. Mosser, F. D'Antona, K. Brogaard, D. Stello, S. McCauliff, Róbert Szabó, Christopher K. Middour, S. Hekker, William J. Chaplin, S. Basu, Paolo Ventura, Jie Li, Alfio Bonanno, Frank Grundahl, V. Silva-Aguirre, T. Kallinger, Marc H. Pinsonneault, Josefina Montalbán, Andrea Miglio, Yvonne Elsworth, H. Kjeldsen, Alessandro Bressan, and A. M. Serenelli
Subjects: Physics, 010308 nuclear & particles physics, Astronomy, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Asteroseismology, Galaxy, Red-giant branch, Stars, Space and Planetary Science, 0103 physical sciences, Range (statistics), Cluster (physics), 010303 astronomy & astrophysics, Red clump, Open cluster
Abstract: Mass loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC6791 and NGC6819. The aim of this work is to constrain the integrated RGB mass loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB (i.e. stars with L
Published: 2011

10. Characterization of red giant stars in the public Kepler data

Author: Khadeejah A. Ibrahim, Todd C. Klaus, J. De Ridder, Jie Li, T. Kallinger, S. Hekker, Yvonne Elsworth, William J. Chaplin, D. Stello, and R. L. Gilliland
Subjects: Physics, Stars, Space and Planetary Science, Red giant, Astrophysics::Solar and Stellar Astrophysics, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics, Kepler, Astrophysics::Galaxy Astrophysics, Large sample
Abstract: The first public release of long-cadence stellar photometric data collected by the NASA Kepler mission has now been made available. In this paper we characterise the red-giant (G-K) stars in this large sample in terms of their solar-like oscillations. We use published methods and well-known scaling relations in the analysis. Just over 70% of the red giants in the sample show detectable solar-like oscillations, and from these oscillations we are able to estimate the fundamental properties of the stars. This asteroseismic analysis reveals different populations: low-luminosity H-shell burning red-giant branch stars, cool high-luminosity red giants on the red-giant branch and He-core burning clump and secondary-clump giants.
Published: 2011

11. Preparation of Kepler light curves for asteroseismic analyses

Author: Christopher K. Middour, Rasmus Handberg, S. Hekker, Yvonne Elsworth, J. Ballot, Mário J. P. F. G. Monteiro, J. Molenda-Zakowicz, Daniel Huber, Christoffer Karoff, H. Kjeldsen, Michael Thompson, Savita Mathur, T. S. Metcalfe, S. McCauliff, D. Stello, R. L. Gilliland, William J. Chaplin, J. M. Jenkins, Jeffrey C. Smith, G. Houdek, R. A. Garcia, J. Christensen-Dalsgaard, Juan Gutiérrez-Soto, T. Appourchaux, and K. Uytterhoeven
Subjects: Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrophysics, Light curve, 01 natural sciences, Kepler, Stars, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar-like oscillations, 010303 astronomy & astrophysics
Abstract: The Kepler mission is providing photometric data of exquisite quality for the asteroseismic study of different classes of pulsating stars. These analyses place particular demands on the pre-processing of the data, over a range of timescales from minutes to months. Here, we describe processing procedures developed by the Kepler Asteroseismic Science Consortium (KASC) to prepare light curves that are optimized for the asteroseismic study of solar-like oscillating stars in which outliers, jumps and drifts are corrected.
Published: 2011

12. Young [$\alpha$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?

Author: Arlette Noels, M. A. G. Maia, Marie Martig, T. Morel, R. A. Garcia, Matthew Shetrone, Keivan G. Stassun, T. S. Rodrigues, Matthias Steinmetz, Sz. Meszaros, T. Kallinger, Paul Harding, Marica Valentini, Josefina Montalbán, D. P. Schneider, M. Schultheis, Friedrich Anders, J. A. Holtzman, R. de Assis Peralta, B. Mosser, S. Hekker, I. Minchev, L. N. da Costa, Andrea Miglio, C. Allende Prieto, Basilio X. Santiago, D. L. Nidever, N. Themeßl, S. R. Majewski, L. Girardi, S. Mathur, K. M. Cunha, F. Baudin, Cristina Chiappini, Timothy C. Beers, K. Pan, Ricardo P. Schiavon, Leibniz-Institut für Astrophysik Potsdam (AIP), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), European Project: 338251,EC:FP7:ERC,ERC-2013-StG,STELLARAGES(2013), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: RED-GIANT STARS, Milky Way, fundamental parameters [stars], MILKY-WAY DISK, Astrophysics, asteroseismology, Astrophysics::Cosmology and Extragalactic Astrophysics, Spectral line, Formacao de galaxias, Galaxy: disk, STELLAR POPULATIONS, SOLAR VICINITY, stellar content [Galaxy], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics, QB, Physics, Galaxy: stellar content, Spiral galaxy, Galactic Center, 1ST YEAR, abundances [Galaxy], Astronomy and Astrophysics, ELEMENTAL ABUNDANCE, Alpha (navigation), CHEMICAL ABUNDANCES, CHEMODYNAMICAL EVOLUTION, Astrophysics - Astrophysics of Galaxies, Chemical evolution, Stars, formation [Galaxy], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Galaxy: formation, Asterosismologia, Galaxy: abundances, stars: fundamental parameters, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], disk [Galaxy], NEARBY STARS, GALACTIC-CENTER
Abstract: We report the discovery of a group of apparently young CoRoT red-giant stars exhibiting enhanced [alpha/Fe] abundance ratios (as determined from APOGEE spectra) with respect to Solar values. Their existence is not explained by standard chemical evolution models of the Milky Way, and shows that the chemical-enrichment history of the Galactic disc is more complex. We find similar stars in previously published samples for which isochrone-ages could be robustly obtained, although in smaller relative numbers, which could explain why these stars have not received prior attention. The young [alpha/Fe]-rich stars are much more numerous in the CoRoT-APOGEE (CoRoGEE) inner-field sample than in any other high-resolution sample available at present, as only CoRoGEE can explore the inner-disc regions and provide ages for its field stars. The kinematic properties of the young [$\alpha$/Fe]-rich stars are not clearly thick-disc like, despite their rather large distances from the Galactic mid-plane. Our tentative interpretation of these and previous intriguing observations in the Milky Way is that these stars were formed close to the end of the Galactic bar, near corotation -- a region where gas can be kept inert for longer times, compared to other regions shocked more frequently by the passage of spiral arms. Moreover, that is where the mass return from older inner-disc stellar generations should be maximal (according to an inside-out disc-formation scenario), further diluting the in-situ gas. Other possibilities to explain these observations (e.g., a recent gas-accretion event) are also discussed., Comment: Letter in press in Astronomy and Astrophysics (5 pages, 4 figures + 2 pages Appendix)
Published: 2015

13. Pulsating red giant stars in eccentric binary systems discovered from Kepler space-based photometry. A sample study and the analysis of KIC 5006817

Author: Aliz Derekas, P. Nemeth, J. De Ridder, A. J. van Marle, J. Vos, R. A. Garcia, Steven Bloemen, Péter Pápics, E. Corsaro, B. Mosser, Andrew Tkachenko, Guy R. Davies, Lionel Siess, Daniel Huber, Conny Aerts, Alex Lobel, Jonas Debosscher, B. L. de Vries, V. S. Schmid, S. Mathur, R. H. Østensen, D. W. Kurtz, Andrej Prsa, K. De Smedt, S. Hekker, Yvonne Elsworth, P. Marcos-Arenal, Krešimir Pavlovski, T. Kallinger, Pieter Degroote, Kelly Hambleton, Paul G. Beck, H. Van Winckel, Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Project: 227224,EC:FP7:ERC,ERC-2008-AdG,PROSPERITY(2009), European Project: 312844,EC:FP7:SPA,FP7-SPACE-2012-1,SPACEINN(2013), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Low Energy Astrophysics (API, FNWI), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: Rotation period, Red giant, Astronomy, Astrophysics, asteroseismology, Astrophysics::Cosmology and Extragalactic Astrophysics, solar-type [Stars], 01 natural sciences, 7. Clean energy, stars: rotation, 0103 physical sciences, Binary star, Astrophysics::Solar and Stellar Astrophysics, Sun: oscillations, 010303 astronomy & astrophysics, Stellar evolution, stars, red giants, oscillations, rotation, binary stars, Astrophysique, Astrophysics::Galaxy Astrophysics, Physics, general [Binaries], 010308 nuclear & particles physics, oscillations [Sun], Asteroseismology, Astronomy and Astrophysics, stars: solar-type, individual: KIC5006817 [Stars], Orbital period, Light curve, Subdwarf, 3. Good health, rotation [Stars], Radial velocity, stars: individual: KIC5006817, binaries: general, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Context. The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red giant stars and binary stars. Seismology allows us to constrain the properties of red giants. In addition to eclipsing binaries, eccentric non-eclipsing binaries that exhibit ellipsoidal modulations have been detected with Kepler. Aims. We aim to study the properties of eccentric binary systems containing a red giant star and to derive the parameters of the primary giant component. Methods. We applied asteroseismic techniques to determine the masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques were applied to extract the parameters of the system and its primary component. Stellar evolution and its effects on the evolution of the binary system were studied from theoretical models. Results. The paper presents the asteroseismic analysis of 18 pulsating red giants in eccentric binary systems, for which masses and radii were constrained. The orbital periods of these systems range from 20 to 440 days. The results of our ongoing radial velocity monitoring programme with the Hermes spectrograph reveal an eccentricity range of e = 0.2 to 0.76. As a case study we present a detailed analysis of KIC 5006817, whose rich oscillation spectrum allows for detailed seismic analysis. From seismology we constrain the rotational period of the envelope to be at least 165 d, which is roughly twice the orbital period. The stellar core rotates 13 times faster than the surface. From the spectrum and radial velocities we expect that the Doppler beaming signal should have a maximum amplitude of 300 ppm in the light curve. Fixing the mass and radius to the asteroseismically determined values, we find from our binary modelling a value of the gravity darkening exponent that is significantly larger than expected. Through binary modelling, we determine the mass of the secondary component to be 0.29 ± 0.03 Mmiddot; Conclusions. For KIC 5006817 we exclude pseudo-synchronous rotation of the red giant with the orbit. The comparison of the results from seismology and modelling of the light curve shows a possible alignment of the rotational and orbital axis at the 2σ level. Red giant eccentric systems could be progenitors of cataclysmic variables and hot subdwarf B stars. © 2014 ESO., SCOPUS: ar.j, info:eu-repo/semantics/published
Published: 2014

14. CoRoT and Kepler results: Solar-like oscillators

Author: S. Hekker and Low Energy Astrophysics (API, FNWI)
Subjects: Physics, Atmospheric Science, K-type main-sequence star, FOS: Physical sciences, Aerospace Engineering, Astronomy, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Asteroseismology, Exoplanet, Kepler-47, Stars, T Tauri star, Geophysics, Convection zone, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, General Earth and Planetary Sciences, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars., Invited review for Advances in Space Research
Published: 2013

15. Study of HD 169392A observed by CoRoT and HARPS

Author: M. Steslicki, Ian W. Roxburgh, Rasmus Handberg, M. Rainer, Yvonne Elsworth, L. Mantegazza, William J. Chaplin, Frédéric Baudin, A. Baglin, T. Roca Cortés, R. Samadi, S. Barceló Forteza, Clara Régulo, C. Catala, Graham A. Verner, S. Hekker, Rafael A. García, B. Mosser, E. Michel, Guy R. Davies, J. Ballot, Othman Benomar, E. Poretti, H. Bruntt, D. Salabert, M. Auvergne, S. Mathur, K. Uytterhoeven, Low Energy Astrophysics (API, FNWI), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astrophysics, Double star, asteroseismology, 01 natural sciences, Asteroseismology, Measure (mathematics), Space exploration, 0103 physical sciences, 010303 astronomy & astrophysics, Stellar evolution, ComputingMilieux_MISCELLANEOUS, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, Mode (statistics), Astronomy and Astrophysics, Radius, methods: data analysis, Stars, stars: individual: HD 169392, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, stars: oscillations, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: The numerous results obtained with asteroseismology thanks to space missions such as CoRoT and Kepler are providing a new insight on stellar evolution. After five years of observations, CoRoT is going on providing high-quality data. We present here the analysis of the double star HD169392 complemented by ground-based spectroscopic observations. This work aims at characterizing the fundamental parameters of the two stars, their chemical composition, the acoustic-mode global parameters including their individual frequencies, and their dynamics. We have analysed HARPS observations of the two stars to retrieve their chemical compositions. Several methods have been used and compared to measure the global properties of acoustic modes and their individual frequencies from the photometric data of CoRoT. The new spectroscopic observations and archival astrometric values suggest that HD169392 is a wide binary system weakly bounded. We have obtained the spectroscopic parameters for both components, suggesting the origin from the same cloud. However, only the mode signature of HD169392 A has been measured within the CoRoT data. The signal-to-noise ratio of the modes in HD169392B is too low to allow any confident detection. We were able to extract mode parameters of modes for l=0, 1, 2, and 3. The study of the splittings and inclination angle gives two possible solutions with splittings and inclination angles of 0.4-1.0 muHz and 20-40 degrees for one case and 0.2-0.5 muHz and 55-86 degrees for the other case. The modeling of this star with the Asteroseismic Modeling Portal led to a mass of 1.15+/-0.01 Ms, a radius of 1.88+/-0.02 Rs, and an age of 4.33+/-0.12 Gyr, where the uncertainties are the internal ones., Comment: 13 pages, 12 Figures, Accepted for publication in A&A
Published: 2013

16. KIC 8410637: a 408-day period eclipsing binary containing a pulsating giant star

Author: S. Frandsen, H. Lehmann, S. Hekker, J. Southworth, J. Debosscher, P. Beck, M. Hartmann, A. Pigulski, G. Kopacki, Z. Kołaczkowski, M. Stȩślicki, A. O. Thygesen, K. Brogaard, Y. Elsworth, and Low Energy Astrophysics (API, FNWI)
Subjects: Physics, 010308 nuclear & particles physics, Red giant, Astronomy and Astrophysics, Radius, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Light curve, 01 natural sciences, Spectral line, Stars, Photometry (astronomy), Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Red clump, Astrophysics::Galaxy Astrophysics, Open cluster
Abstract: Context. Detached eclipsing binaries (dEBs) are ideal targets for accurately measuring the masses and radii of their component stars. If at least one of the stars has evolved off the main sequence (MS), the masses and radii give a strict constraint on the age of the stars. Several dEBs containing a bright K giant and a fainter MS star have been discovered by the Kepler satellite. The mass and radius of a red giant (RG) star can also be derived from its asteroseismic signal. The parameters determined in this way depend on stellar models and may contain systematic errors. It is important to validate the asteroseismically determined mass and radius with independent methods. This can be done when stars are members of stellar clusters or members of dEBs.Aims. This paper presents an analysis of the dEB system KIC 8410637, which consists of an RG and an MS star. The aim is to derive accurate masses and radii for both components and provide the foundation for a strong test of the asteroseismic method and the accuracy of the deduced mass, radius, and age.Methods. We analysed high-resolution, high-signal-to-noise spectra from three different spectrographs. We also calculated a fit to the Kepler light curve and used ground-based photometry to determine the flux ratios between the component stars in the BVRI passbands.Results. We measured the masses and radii of the stars in the dEB, and the classical parameters Teff, log g, and [Fe/H] from the spectra and ground-based photometry. The RG component of KIC 8410637 is most likely in the core helium-burning red clump phase of evolution and has an age and composition that are very similar to the stars in the open cluster NGC 6819. The mass of the RG in KIC 8410637 should therefore be similar to the mass of RGs in NGC 6819, thus lending support to the latest version of the asteroseismic scaling relations. This is the first direct measurement of both mass and radius for an RG to be compared with values for RGs from asteroseismic scaling relations thereby providing an accurate comparison. We find excellent agreement between log g values derived from the binary analysis and asteroseismic scaling relations.Conclusions. We have determined the masses and radii of the two stars in the binary accurately. A detailed asteroseismic analysis will be presented in a forthcoming paper, allowing an informative comparison between the parameters determined for the dEB and from asteroseismology.
Published: 2013

17. Fundamental properties of stars using asteroseismology from Kepler and CoRoT and interferometry from the CHARA Array

Author: J. Christensen-Dalsgaard, Martin C. Stumpe, Chris Farrington, Andrea Miglio, Michael Ireland, Neal J. Turner, Joanna Molenda-Żakowicz, H. A. McAlister, Luca Casagrande, H. Kjeldsen, P. J. Goldfinger, K. Uytterhoeven, H. Bruntt, Antonio Frasca, Vicente Maestro, V. Silva Aguirre, T. ten Brummelaar, Michael Thompson, T. S. Metcalfe, Daniel Huber, R. A. Garcia, T. R. Bedding, S. G. Sousa, Thomas Barclay, Timothy R. White, I. M. Brandão, M. S. Cunha, R. L. Gilliland, Christopher J. Burke, J. Sturmann, Marc H. Pinsonneault, S. Hekker, William J. Chaplin, Steven D. Kawaler, L. Sturmann, L. Piau, Mário J. P. F. G. Monteiro, Gail Schaefer, J. De Ridder, D. Stello, and Low Energy Astrophysics (API, FNWI)
Subjects: oscillations (including pulsations) [stars], Red giant, FOS: Physical sciences, Astrophysics, 7. Clean energy, 01 natural sciences, Asteroseismology, CHARA array, photometric [techniques], Frequency separation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Oscillation, Subgiant, Astronomy and Astrophysics, interferometric [techniques], Stars, Interferometry, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, late-type [stars], Astrophysics::Earth and Planetary Astrophysics
Abstract: We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos parallaxes, asteroseismic densities, bolometric fluxes and high-resolution spectroscopy we derive a full set of near model-independent fundamental properties for the sample. We first use these properties to test asteroseismic scaling relations for the frequency of maximum power (nu_max) and the large frequency separation (Delta_nu). We find excellent agreement within the observational uncertainties, and empirically show that simple estimates of asteroseismic radii for main-sequence stars are accurate to, Comment: 18 pages, 12 figures, 7 tables; accepted for publication in ApJ
Published: 2012
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18. DETECTION OF SOLAR-LIKE OSCILLATIONS, OBSERVATIONAL CONSTRAINTS, AND STELLAR MODELS FORθCYG, THE BRIGHTEST STAR OBSERVED BY THEKEPLERMISSION

Author: Andrea Miglio, Lars A. Buchhave, D. W. Kurtz, Amanda P. Doyle, Daniel Huber, Péter Pápics, Giovanni Catanzaro, Joanna Molenda-Żakowicz, G. Doğan, Tiago L. Campante, Antonio Frasca, J. A. Guzik, Martin Still, Maryline Briquet, William J. Chaplin, Fergal Mullally, Diana Dragomir, T. S. Metcalfe, J. Christensen-Dalsgaard, Barry Smalley, Sarbani Basu, Rasmus Handberg, M. Gruberbauer, O. Benomar, Timothy R. White, Jason F. Rowe, B. Mosser, Guy R. Davies, T. Appourchaux, J. Ballot, S. G. Sousa, Conny Aerts, K. Uytterhoeven, Patrick Gaulme, S. T. Bryson, Simon J. Murphy, Clara Régulo, S. Hekker, H. Bruntt, D. W. Latham, V. Ripepi, Victoria Antoci, Rafael A. García, Tabetha S. Boyajian, Christoffer Karoff, Holger Lehmann, D. Salabert, G. Houdek, S. Mathur, Yvonne Elsworth, T. R. Bedding, D. Stello, P. Mathias, R. L. Gilliland, H. Kjeldsen, Institute for Astronomy [Vienna], University of Vienna [Vienna], Stellar Astrophysics Centre [Aarhus] (SAC), Aarhus University [Aarhus], Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Geosciences [Lubbock], Texas Tech University [Lubbock] (TTU), Visio per computador i robotica (VICOROB), Universitat de Girona (UdG), Department of Physics and Astronomy [Aarhus], Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Observatoire de Paris, Université Paris sciences et lettres (PSL), National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy and Physics [Halifax], Saint Mary's University [Halifax], Indian Institute of Astrophysics (IIA), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), INAF - Osservatorio Astronomico di Capodimonte (OAC), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Sydney Institute for Astronomy (SIfA), The University of Sydney, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), Guzik J.A., Houdek G., Chaplin W.J., Smalley B., Kurtz D.W., Gilliland R.L., Mullally F., Rowe J.F., Bryson S.T., Still M.D., Antoci V., Appourchaux T., Basu S., Bedding T.R., Benomar O., Garcia R.A., Huber D., Kjeldsen H., Latham D.W., Metcalfe T.S., Papics P.I., White T.R., Aerts C., Ballot J., Boyajian T.S., Briquet M., Bruntt H., Buchhave L.A., Campante T.L., Catanzaro G., Christensen-Dalsgaard J., Davies G.R., Dogan G., Dragomir D., Doyle A.P., Elsworth Y., Frasca A., Gaulme P., Gruberbauer M., Handberg R., Hekker S., Karoff C., Lehmann H., Mathias P., Mathur S., Miglio A., Molenda-Zakowicz J., Mosser B., Murphy S.J., Regulo C., Ripepi V., Salabert D., Sousa S.G., Stello D., Uytterhoeven K., Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), PSL Research University (PSL), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Wrocław [Poland], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur
Subjects: solar-type [stars], GAMMA DORADUS STARS, Astronomy, fundamental parameters [stars], EXOPLANET HOST STARS, INFRARED FLUX METHOD, Solar radius, F500, asteroseismology, Astrophysics, EFFECTIVE TEMPERATURES, 01 natural sciences, Apparent magnitude, Angular diameter, 0103 physical sciences, Solar-like oscillations, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, QB, stars: interior, interiors [stars], [PHYS]Physics [physics], Physics, Solar mass, 010308 nuclear & particles physics, stars: solar-type, Astronomy and Astrophysics, stars: fundamental parameter, Radius, A-TYPE, SPECTROSCOPIC PARAMETERS, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, DELTA SCT, F-TYPE STARS, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Parallax, MAIN-SEQUENCE STARS, NEARBY STARS
Abstract: $\theta$ Cygni is an F3 spectral-type main-sequence star with visual magnitude V=4.48. This star was the brightest star observed by the original Kepler spacecraft mission. Short-cadence (58.8 s) photometric data using a custom aperture were obtained during Quarter 6 (June-September 2010) and subsequently in Quarters 8 and 12-17. We present analyses of the solar-like oscillations based on Q6 and Q8 data, identifying angular degree $l$ = 0, 1, and 2 oscillations in the range 1000-2700 microHz, with a large frequency separation of 83.9 plus/minus 0.4 microHz, and frequency with maximum amplitude 1829 plus/minus 54 microHz. We also present analyses of new ground-based spectroscopic observations, which, when combined with angular diameter measurements from interferometry and Hipparcos parallax, give T_eff = 6697 plus/minus 78 K, radius 1.49 plus/minus 0.03 solar radii, [Fe/H] = -0.02 plus/minus 0.06 dex, and log g = 4.23 plus/minus 0.03. We calculate stellar models matching the constraints using several methods, including using the Yale Rotating Evolution Code and the Asteroseismic Modeling Portal. The best-fit models have masses 1.35-1.39 solar masses and ages 1.0-1.6 Gyr. theta Cyg's T_eff and log g place it cooler than the red edge of the gamma Doradus instability region established from pre-Kepler ground-based observations, but just at the red edge derived from pulsation modeling. The pulsation models show gamma Dor gravity-mode pulsations driven by the convective-blocking mechanism, with frequencies of 1 to 3 cycles/day (11 to 33 microHz). However, gravity modes were not detected in the Kepler data, one signal at 1.776 cycles/day (20.56 microHz) may be attributable to a faint, possibly background, binary. Asteroseismic studies of theta Cyg and other A-F stars observed by Kepler and CoRoT, will help to improve stellar model physics and to test pulsation driving mechanisms., Comment: Accepted for Publication in The Astrophysical Journal, July 1, 2016
Published: 2016

19. Asteroseismology of the Solar Analogs 16 Cyg A and B from Kepler Observations

Author: T. Stahn, S. Mathur, T. S. Metcalfe, J. Christensen-Dalsgaard, T. Appourchaux, Martin Still, H. M. Antia, R. L. Gilliland, B. Mosser, Guy R. Davies, G. Doğan, H. Kjeldsen, P. Eggenberger, D. Stello, Yvonne Elsworth, R. A. Garcia, O. L. Creevey, S. D. Kawaler, S. Basu, Andrea Miglio, Christoffer Karoff, William J. Chaplin, T. R. Bedding, S. T. Bryson, I. M. Brandão, D. Salabert, Mutlu Yildiz, S. Hekker, Laurent Gizon, Z. Celik, Clara Régulo, O. Benomar, Khadeejah A. Ibrahim, Todd C. Klaus, Jie Li, Sébastien Deheuvels, Roger T. Howe, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Ege Üniversitesi, and Low Energy Astrophysics (API, FNWI)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: interiors, 01 natural sciences, 7. Clean energy, Asteroseismology, Photometry (optics), Spitzer Space Telescope, 0103 physical sciences, Differential rotation, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, Earth and Planetary Astrophysics (astro-ph.EP), 010308 nuclear & particles physics, Astronomy and Astrophysics, stars: solar-type, Orbital period, Stars, Astrophysics - Solar and Stellar Astrophysics, Convection zone, 13. Climate action, Space and Planetary Science, stars: individual (HD 186408, HD 186427), stars: fundamental parameters, stars: oscillations, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: WOS: 000301297500010, The evolved solar-type stars 16 Cyg A and B have long been studied as solar analogs, yielding a glimpse into the future of our own Sun. The orbital period of the binary system is too long to provide meaningful dynamical constraints on the stellar properties, but asteroseismology can help because the stars are among the brightest in the Kepler field. We present an analysis of three months of nearly uninterrupted photometry of 16 Cyg A and B from the Kepler space telescope. We extract a total of 46 and 41 oscillation frequencies for the two components, respectively, including a clear detection of octupole (l = 3) modes in both stars. We derive the properties of each star independently using the Asteroseismic Modeling Portal, fitting the individual oscillation frequencies and other observational constraints simultaneously. We evaluate the systematic uncertainties from an ensemble of results generated by a variety of stellar evolution codes and fitting methods. The optimal models derived by fitting each component individually yield a common age (t = 6.8 +/- 0.4 Gyr) and initial composition (Z(i) = 0.024 +/- 0.002, Y-i = 0.25 +/- 0.01) within the uncertainties, as expected for the components of a binary system, bolstering our confidence in the reliability of asteroseismic techniques. The longer data sets that will ultimately become available will allow future studies of differential rotation, convection zone depths, and long-term changes due to stellar activity cycles., NASA's Science Mission Directorate; NASANational Aeronautics & Space Administration (NASA) [NNX09AE59G]; National Science FoundationNational Science Foundation (NSF) [NSF PHY05-51164]; Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC) [ST/J001163/1], Funding for this Discovery mission is provided by NASA's Science Mission Directorate. This work was supported in part by NASA grant NNX09AE59G. Computational time on Kraken at the National Institute of Computational Sciences was provided through NSF TeraGrid allocation TG-AST090107. We acknowledge the KITP staff at UCSB for their warm hospitality during the research program "Asteroseismology in the Space Age." This research was supported in part by the National Science Foundation under Grant No. NSF PHY05-51164. The authors thank Jeff Hall, Todd Henry, Dave Soderblom, and Russel White for helpful discussions, as well as the entire Kepler team, without whom these results would not be possible. We also thank all funding councils and agencies that have supported the activities of the Kepler Asteroseismic Science Consortium Working Group 1, including the Pale Blue Dot Project hosted by White Dwarf Research Corporation (http://whitedwarf.org/palebluedot/).
Published: 2012

20. An asteroseismic membership study of the red giants in three open clusters observed by Kepler: NGC6791, NGC6819, and NGC6811

Author: B. Mosser, K. Brogaard, Daniel Huber, S. Meibom, S. Mathur, Martin Still, Róbert Szabó, William J. Chaplin, J. Christensen-Dalsgaard, S. Hekker, T. R. Bedding, A. M. Serenelli, Joanna Molenda-Żakowicz, S. Basu, J. M. Jenkins, Frank Grundahl, B. Wohler, T. Kallinger, R. A. Garcia, D. Stello, H. Kjeldsen, Yvonne Elsworth, R. L. Gilliland, Sydney Institute for Astronomy (SIfA), Harvard-Smithsonian Center for Astrophysics, Space Telescope Science Institute (STScI), Department of Physics and Astronomy, Aarhus University, School of Physics and Astronomy, University of Birmingham, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut für Astronomie, Universität Wien (IfA), High Altitude Observatory, National Center for Atmospheric Research, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Astronomy, Yale University, Instytut Astronomiczny, Uniwersytet Wroclawski, Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, SETI Institute, NASA Ames Research Center, Moffett Field, Instituto de Ciencias del Espacio-Institut d'Estudis Espacials de Catalunya, and Orbital Sciences Corporation, NASA Ames Research Center, Moffett Field
Subjects: Physics, 010308 nuclear & particles physics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Kepler, Asteroseismology, Photometry (optics), Stars, Star cluster, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Cluster (physics), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Open cluster
Abstract: Studying star clusters offers significant advances in stellar astrophysics due to the combined power of having many stars with essentially the same distance, age, and initial composition. This makes clusters excellent test benches for verification of stellar evolution theory. To fully exploit this potential, it is vital that the star sample is uncontaminated by stars that are not members of the cluster. Techniques for determining cluster membership therefore play a key role in the investigation of clusters. We present results on three clusters in the Kepler field of view based on a newly established technique that uses asteroseismology to identify fore- or background stars in the field, which demonstrates advantages over classical methods such as kinematic and photometry measurements. Four previously identified seismic non-members in NGC6819 are confirmed in this study, and three additional non-members are found -- two in NGC6819 and one in NGC6791. We further highlight which stars are, or might be, affected by blending, which needs to be taken into account when analysing these Kepler data., 12 pages, 9 figures, 5 tables, accepted by ApJ
Published: 2011

21. Constructing a One-solar-mass Evolutionary Sequence Using Asteroseismic Data from Kepler

Author: Alfio Bonanno, Axel Weiss, D. Salabert, V. Silva Aguirre, Mário J. P. F. G. Monteiro, Graham A. Verner, G. Houdek, A.-M. Broomhall, E. Corsaro, R. L. Gilliland, Jessie L. Christiansen, H. Bruntt, William J. Chaplin, J. Molenda-Zakowicz, A. M. Serenelli, S. G. Sousa, T. Appourchaux, Savita Mathur, D. A. Caldwell, J. Christensen-Dalsgaard, Timothy R. Bedding, Ralph Schönrich, Michael Thompson, B. Mosser, H. Kjeldsen, J. Ballot, S. Basu, T. S. Metcalfe, B. Wohler, Timothy R. White, Daniel Huber, R. A. Garcia, Rasmus Handberg, Andrea Miglio, Yvonne Elsworth, T. L. Campante, S. D. Kawaler, Luca Casagrande, Christoffer Karoff, S. Hekker, Patrick Gaulme, D. Stello, Laboratoire Hippolyte Fizeau (FIZEAU), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), and Low Energy Astrophysics (API, FNWI)
Subjects: Physics, Solar mass, Field (physics), 010308 nuclear & particles physics, Oscillation, FOS: Physical sciences, Astronomy and Astrophysics, Observable, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asteroseismology, Stars, Photometry (astronomy), Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Frequency separation, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics
Abstract: Asteroseismology of solar-type stars has entered a new era of large surveys with the success of the NASA \textit{Kepler} mission, which is providing exquisite data on oscillations of stars across the Hertzprung-Russell (HR) diagram. From the time-series photometry, the two seismic parameters that can be most readily extracted are the large frequency separation ($\Delta\nu$) and the frequency of maximum oscillation power ($\nu_\mathrm{max}$). After the survey phase, these quantities are available for hundreds of solar-type stars. By scaling from solar values, we use these two asteroseismic observables to identify for the first time an evolutionary sequence of 1-M$_\odot$ field stars, without the need for further information from stellar models. Comparison of our determinations with the few available spectroscopic results shows an excellent level of agreement. We discuss the potential of the method for differential analysis throughout the main-sequence evolution, and the possibility of detecting twins of very well-known stars., Comment: 17 pages, 4 figures, accepted in ApJL
Published: 2011

22. Granulation in Red Giants: Observations by the Kepler Mission and Three-dimensional Convection Simulations

Author: S. Mathur, Daniel Huber, R. A. Garcia, H. Kjeldsen, William J. Chaplin, Derek L. Buzasi, Yvonne Elsworth, R. Trampedach, Antonio Jiménez, T. R. Bedding, D. Stello, Steven J. Hale, Fergal Mullally, J. De Ridder, T. Kallinger, Karen Kinemuchi, S. Hekker, Clara Régulo, Susan E. Thompson, B. Mosser, J. Ballot, High Altitude Observatory, National Center for Atmospheric Research, Astronomical Institute Anton Pannekoek, University of Amsterdam, University of Colorado, Joint Institute for Laboratory Astrophysics (JILA), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut für Astronomie, Universität Wien (IfA), Eureka Scientific, Oakland, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Sydney Institute for Astronomy (SIfA), Universidad de La Laguna [Tenerife - SP] (ULL), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Etoile, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), School of Physics and Astronomy, University of Birmingham, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, Danish AsteroSeismology Centre (DASC), SETI Institute, NASA Ames Research Center, Moffett Field, and Low Energy Astrophysics (API, FNWI)
Subjects: Physics, Photosphere, Astronomy and Astrophysics, Astrophysics, Effective temperature, Surface gravity, Asteroseismology, Stars, Granulation, Convection zone, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Red clump, Astrophysics::Galaxy Astrophysics
Abstract: The granulation pattern that we observe on the surface of the Sun is due to hot plasma from the interior rising to the photosphere where it cools down, and descends back into the interior at the edges of granules. This is the visible manifestation of convection taking place in the outer part of the solar convection zone. Because red giants have deeper convection zones and more extended atmospheres than the Sun, we cannot a priori assume that granulation in red giants is a scaled version of solar granulation. Until now, neither observations nor 1D analytical convection models could put constraints on granulation in red giants. However, thanks to asteroseismology, this study can now be performed. The resulting parameters yield physical information about the granulation. We analyze \sim1000 red giants that have been observed by Kepler during 13 months. We fit the power spectra with Harvey-like profiles to retrieve the characteristics of the granulation (time scale tau_gran and power P_gran). We also introduce a new time scale, tau_eff, which takes into account that different slopes are used in the Harvey functions. We search for a correlation between these parameters and the global acoustic-mode parameter (the position of maximum power, nu_max) as well as with stellar parameters (mass, radius, surface gravity (log g) and effective temperature (T_eff)). We show that tau_eff nu_max^{-0.89} and P_gran nu_max^{-1.90}, which is consistent with the theoretical predictions. We find that the granulation time scales of stars that belong to the red clump have similar values while the time scales of stars in the red-giant branch are spread in a wider range. Finally, we show that realistic 3D simulations of the surface convection in stars, spanning the (T_eff, log g)-range of our sample of red giants, match the Kepler observations well in terms of trends.
Published: 2011

23. Solar-like Oscillations in KIC 11395018 and KIC 11234888 from 8 Months of Kepler Data

Author: S. D. Kawaler, J. Christensen-Dalsgaard, S. E. Seader, Mário J. P. F. G. Monteiro, Elisa V. Quintana, Timothy R. Bedding, Tiago L. Campante, Daniel Huber, H. Kjeldsen, T. S. Metcalfe, Rasmus Handberg, Graham A. Verner, Yvonne Elsworth, D. T. Sanderfer, Patrick Gaulme, O. L. Creevey, E. Corsaro, R. L. Gilliland, I. M. Brandão, S. Hekker, Michael Thompson, Timothy R. White, B. Mosser, J. Ballot, Christoffer Karoff, T. Appourchaux, G. Doğan, William J. Chaplin, Steven J. Hale, Rafael A. García, O. Benomar, J. Molenda-Zakowicz, Savita Mathur, Alfio Bonanno, D. Salabert, G. Houdek, Clara Régulo, High Altitude Observatory, National Center for Atmospheric Research, Danish AsteroSeismology Centre (DASC), Centro de Astrofísica, Universidade do Porto, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Sydney Institute for Astronomy (SIfA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), School of Physics and Astronomy, University of Birmingham, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), INAF-Osservatorio Astrofisico di Catania (INAF-OACt), Universidad de La Laguna [Tenerife - SP] (ULL), Astronomy Unit, Queen Mary, Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Institut für Astronomie, Universität Wien (IfA), Astronomical Institute, University of Wroclaw, Space Telescope Science Institute (STScI), Department of Physics and Astronomy, Iowa State University, SETI Institute, NASA Ames Research Center, Moffett Field, and Low Energy Astrophysics (API, FNWI)
Subjects: Physics, Oscillation, Stellar rotation, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Radius, Stellar classification, Stars, Laser linewidth, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Solar-like oscillations, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Envelope (waves)
Abstract: We analyze the photometric short-cadence data obtained with the Kepler Mission during the first eight months of observations of two solar-type stars of spectral types G and F: KIC 11395018 and KIC 11234888 respectively, the latter having a lower signal-to-noise ratio compared to the former. We estimate global parameters of the acoustic (p) modes such as the average large and small frequency separations, the frequency of the maximum of the p-mode envelope and the average linewidth of the acoustic modes. We were able to identify and to measure 22 p-mode frequencies for the first star and 16 for the second one even though the signal-to-noise ratios of these stars are rather low. We also derive some information about the stellar rotation periods from the analyses of the low-frequency parts of the power spectral densities. A model-independent estimation of the mean density, mass and radius are obtained using the scaling laws. We emphasize the importance of continued observations for the stars with low signal-to-noise ratio for an improved characterization of the oscillation modes. Our results offer a preview of what will be possible for many stars with the long data sets obtained during the remainder of the mission., Comment: 39 pages, 9 figures. Accepted for publication in ApJ
Published: 2011

24. Non-radial oscillations in the red giant HR7349 measured by CoRoT

Author: T. Morel, Andrea Miglio, T. Kallinger, Josefina Montalbán, M. Auvergne, J. De Ridder, R. Samadi, S. Hekker, C. Catala, A. P. Hatzes, Caroline Barban, Fabien Carrier, E. Michel, Werner W. Weiss, A. Baglin, F. Baudin, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Astronomie du LESIA, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Thüringer Landessternwarte, Tautenburg Observatory, School of Physics and Astronomy, University of Birmingham, Institut für Astronomie, Universität Wien (IfA), and Institut d'Astrophysique, Géophysique et Océanographie, Université de Liège
Subjects: Convection, Physics, Red giant, Spectral density, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Acoustic wave, Astrophysics::Cosmology and Extragalactic Astrophysics, Asteroseismology, Stars, Amplitude, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Speed of sound, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: Convection in red giant stars excites resonant acoustic waves whose frequencies depend on the sound speed inside the star, which in turn depends on the properties of the stellar interior. Therefore, asteroseismology is the most robust available method for probing the internal structure of red giant stars. Solar-like oscillations in the red giant HR7349 are investigated. Our study is based on a time series of 380760 photometric measurements spread over 5 months obtained with the CoRoT satellite. Mode parameters were estimated using maximum likelihood estimation of the power spectrum. The power spectrum of the high-precision time series clearly exhibits several identifiable peaks between 19 and 40 uHz showing regularity with a mean large and small spacing of Dnu = 3.47+-0.12 uHz and dnu_02 = 0.65+-0.10 uHz. Nineteen individual modes are identified with amplitudes in the range from 35 to 115 ppm. The mode damping time is estimated to be 14.7+4.7-2.9 days., 8 pages, A&A accepted
Published: 2010

25. Asteroseismology of solar-type stars with Kepler I:Data analysis

Author: Arlette Noels, R. Trampedach, Sarbani Basu, Graham A. Verner, Dennis Stello, T. Appourchaux, T. S. Metcalfe, J. A. Guzik, Patrick Gaulme, Tiago L. Campante, Michael Gruberbauer, K. H. Sato, K. Uytterhoeven, Friedrich Kupka, J. Christensen-Dalsgaard, Markus Roth, M. Martic, S. Hekker, Katia Biazzo, Mário J. P. F. G. Monteiro, J. H. M. M. Schmitt, William J. Chaplin, B. Mosser, J. Molenda-Zakowicz, Christoffer Karoff, T. Roca Cortés, Rita Ventura, Robert W. Noyes, R. L. Gilliland, Rasmus Handberg, Savita Mathur, B. Leroy, Michael Thompson, Paul Wilson, Kevin Belkacem, P. Eggenberger, Clara Régulo, Rafael A. García, Yvonne Elsworth, D. Salabert, G. Houdek, Stéphane Mathis, Hans-Günter Ludwig, Stephen T. Fletcher, Ian W. Roxburgh, Timothy R. Bedding, Margarida S. Cunha, Hans Kjeldsen, M. D. Suran, School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Institute for Astronomy [Vienna], University of Vienna [Vienna], Scientific Computing Division [Boulder] (SCD), National Center for Atmospheric Research [Boulder] (NCAR), Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto, Departamento de Física e Astronomia [Porto] (DFA/FCUP), Faculdade de Ciências da Universidade do Porto (FCUP), Universidade do Porto-Universidade do Porto, School of Mathematics and Statistics [Sheffield] (SoMaS), University of Sheffield [Sheffield], Space Telescope Science Institute (STSci), Department of Astronomy [New Haven], Yale University [New Haven], Sydney Institute for Astronomy (SIfA), The University of Sydney, Geneva Observatory, University of Geneva [Switzerland], Materials and Engineering Research Institute [Sheffield] (MERI), Sheffield Hallam University, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Instituto de Astrofisica de Canarias (IAC), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Astronomy Unit [London] (AU), Queen Mary University of London (QMUL), Département d'astrophysique, Géophysique et Océanographie (AGO), Université de Liège, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Department of Astronomy and Physics [Halifax], Saint Mary's University [Halifax], Los Alamos National Laboratory (LANL), Faculty of Mathematics [Vienna], Zentrum für Astronomie der Universität Heidelberg (ZAH), Universität Heidelberg [Heidelberg], Smithsonian Astrophysical Observatory, Smithsonian Institution, Kiepenheuer-Institut für Sonnenphysik (KIS), Observatoire de Haute-Provence (OHP), Institut Pythéas (OSU PYTHEAS), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut de Recherche pour le Développement (IRD), Astronomical Institute of Romanian Academy, Romanian Academy, Joint Institute for Laboratory Astrophysics (JILA), National Institute of Standards and Technology [Gaithersburg] (NIST)-University of Colorado [Boulder], INAF - Osservatorio Astrofisico di Catania (OACT), Institute of Theoretical Astrophysics [Oslo], University of Oslo (UiO), Nordic Optical Telescope (NOT), Danish Natural Sciences Research Council., Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universidade do Porto = University of Porto, Universidade do Porto = University of Porto-Universidade do Porto = University of Porto, Université de Genève = University of Geneva (UNIGE), Universität Heidelberg [Heidelberg] = Heidelberg University, Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), University of Wrocław [Poland], Universidade do Porto [Porto], Departamento de Física e Astronomia [Porto], Materials and Engineering Research Institute [Sheffield], HEPPI - LATMOS, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: 010504 meteorology & atmospheric sciences, Data analysis, FOS: Physical sciences, Astrophysics, Stars: late-type, Star (graph theory), Type (model theory), 01 natural sciences, Kepler, Asteroseismology, Spectral line, 0103 physical sciences, Stars: oscillations, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Oscillation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Stars: interiors, Astrophysics::Earth and Planetary Astrophysics
Abstract: We report on the first asteroseismic analysis of solar-type stars observed by Kepler. Observations of three G-type stars, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: About 20 modes of oscillation can clearly be distinguished in each star. We discuss the appearance of the oscillation spectra, including the presence of a possible signature of faculae, and the presence of mixed modes in one of the three stars., Comment: 5 pages, 4 figure, submitted to Astronomische Nachrichten
Published: 2010

26. Asteroseismology of red giants from the first four months of Kepler data: Fundamental stellar parameters

Author: S. Frandsen, S. Hekker, S. Basu, Yvonne Elsworth, R. L. Gilliland, J. De Ridder, J. Christensen-Dalsgaard, M. Gruberbauer, J. M. Matthews, D. Stello, William J. Borucki, R. A. Garcia, S. Mathur, T. Kallinger, H. Kjeldsen, William J. Chaplin, Daniel Huber, T. R. Bedding, H. Bruntt, David G. Koch, B. Mosser, Institut für Astronomie, Universität Wien (IfA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), School of Physics and Astronomy, University of Birmingham, Sydney Institute for Astronomy (SIfA), High Altitude Observatory, National Center for Atmospheric Research, Department of Astronomy, Yale University, Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Danish AsteroSeismology Centre (DASC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institute for Computational Astrophysics, Department of Astronomy and Physics, Saint Marys University, Department of Physics and Astronomy, University of British Columbia, National Aeronautics and Space Administration, Ames Research Center, Department of Physics and Astronomy, Aarhus University, and Space Telescope Science Institute (STScI)
Subjects: Stellar population, Metallicity, Population, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Stellar classification, 01 natural sciences, Asteroseismology, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Stellar structure, Solar-like oscillations, education, 010303 astronomy & astrophysics, Red clump, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, education.field_of_study, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Clear power excess in a frequency range typical for solar-type oscillations in red giants has been detected in more than 1000 stars, which have been observed during the first 138 days of the science operation of the NASA Kepler satellite. This sample includes stars in a wide mass and radius range with spectral types G and K, extending in luminosity from the bottom of the giant branch up to high-luminous red giants. The high-precision asteroseismic observations with Kepler provide a perfect source for testing stellar structure and evolutionary models, as well as investigating the stellar population in our Galaxy. We fit a global model to the observed frequency spectra, which allows us to accurately estimate the granulation background signal and the global oscillation parameters, such as the frequency of maximum oscillation power. We find regular patterns of radial and non-radial oscillation modes and use a new technique to automatically identify the mode degree and the characteristic frequency separations between consecutive modes of the same spherical degree. In most cases, we can also measure the small separation. The seismic parameters are used to estimate stellar masses and radii and to place the stars in an H-R diagram by using an extensive grid of stellar models that covers a wide parameter range. Using Bayesian techniques throughout our analysis allows us to determine reliable uncertainties for all parameters. We provide accurate seismic parameters and their uncertainties for a large sample of red giants and determine their asteroseismic fundamental parameters. We investigate the influence of the stars' metallicities on their positions in the H-R diagram. We study the red-giant populations in the red clump and bump and compare them to a synthetic population and find a mass and metallicity gradient in the red clump and clear evidence of a secondary-clump population., Comment: accepted for publication in Astronomy and Astrophysics, 14 pages, 13 figures
Published: 2010

27. The Asteroseismic Potential of Kepler: First Results for Solar-Type Stars

Author: W. J. Chaplin, T. Appourchaux, Y. Elsworth, R. A. García, G. Houdek, C. Karoff, T. S. Metcalfe, J. Molenda-Żakowicz, M. J. P. F. G. Monteiro, M. J. Thompson, T. M. Brown, J. Christensen-Dalsgaard, R. L. Gilliland, H. Kjeldsen, W. J. Borucki, D. Koch, J. M. Jenkins, J. Ballot, S. Basu, M. Bazot, T. R. Bedding, O. Benomar, A. Bonanno, I. M. Brandão, H. Bruntt, T. L. Campante, O. L. Creevey, M. P. Di Mauro, G. Doğan, S. Dreizler, P. Eggenberger, L. Esch, S. T. Fletcher, S. Frandsen, N. Gai, P. Gaulme, R. Handberg, S. Hekker, R. Howe, D. Huber, S. G. Korzennik, J. C. Lebrun, S. Leccia, M. Martic, S. Mathur, B. Mosser, R. New, P.-O. Quirion, C. Régulo, I. W. Roxburgh, D. Salabert, J. Schou, S. G. Sousa, D. Stello, G. A. Verner, T. Arentoft, C. Barban, K. Belkacem, S. Benatti, K. Biazzo, P. Boumier, P. A. Bradley, A.-M. Broomhall, D. L. Buzasi, R. U. Claudi, M. S. Cunha, F. D'Antona, S. Deheuvels, A. Derekas, A. García Hernández, M. S. Giampapa, M. J. Goupil, M. Gruberbauer, J. A. Guzik, S. J. Hale, M. J. Ireland, L. L. Kiss, I. N. Kitiashvili, K. Kolenberg, H. Korhonen, A. G. Kosovichev, F. Kupka, Y. Lebreton, B. Leroy, H.-G. Ludwig, S. Mathis, E. Michel, A. Miglio, J. Montalbán, A. Moya, A. Noels, R. W. Noyes, P. L. Pallé, L. Piau, H. L. Preston, T. Roca Cortés, M. Roth, K. H. Sato, J. Schmitt, A. M. Serenelli, V. Silva Aguirre, I. R. Stevens, J. C. Suárez, M. D. Suran, R. Trampedach, S. Turck-Chièze, K. Uytterhoeven, R. Ventura, P. A. Wilson, School of Physics and Astronomy [Birmingham], University of Birmingham [Birmingham], Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institute for Astronomy [Vienna], University of Vienna [Vienna], High Altitude Observatory (HAO), National Center for Atmospheric Research [Boulder] (NCAR), Astronomical Institute [Wroclaw], University of Wrocław [Poland] (UWr), Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto, School of Mathematics and Statistics [Sheffield] (SoMaS), University of Sheffield [Sheffield], Las Cumbres Observatory (LCO), Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], Space Telescope Science Institute (STSci), NASA Ames Research Center (ARC), SETI Institute, Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées, Department of Astronomy [New Haven], Yale University [New Haven], Sydney Institute for Astronomy (SIfA), The University of Sydney, INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Observatoire de Paris, Université Paris sciences et lettres (PSL), Departamento de Astrofísica [La laguna], Universidad de La Laguna [Tenerife - SP] (ULL), Instituto de Astrofisica de Canarias (IAC), Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Institut für Astrophysik [Göttingen], Georg-August-University [Göttingen], Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Materials and Engineering Research Institute [Sheffield] (MERI), Sheffield Hallam University, Beijing Normal University (BNU), National Solar Observatory [Tucson] (NSO/Tucson), National Science Foundation [Arlington] (NSF)-Association of Universities for Research in Astronomy (AURA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), INAF - Osservatorio Astronomico di Capodimonte (OAC), Indian Institute of Astrophysics (IIA), Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Canadian Space Agency (CSA), Astronomy Unit [London] (AU), Queen Mary University of London (QMUL), Hansen Experimental Physics Lab [Stanford] (HEPL), Stanford University, Département d'astrophysique, Géophysique et Océanographie (AGO), Université de Liège, Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Universita degli Studi di Padova, INAF - Osservatorio Astrofisico di Arcetri (OAA), Los Alamos National Laboratory (LANL), Eureka Scientific, INAF - Osservatorio Astronomico di Padova (OAPD), INAF - Osservatorio Astronomico di Roma (OAR), Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Department of Astronomy and Physics [Halifax], Saint Mary's University [Halifax], Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut d'Astrophysique et de Géophysique [Liège], Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universidade do Porto = University of Porto, Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Georg-August-University = Georg-August-Universität Göttingen, Université de Genève = University of Geneva (UNIGE), Harvard University-Smithsonian Institution, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Università degli Studi di Padova = University of Padua (Unipd), and Faculdade de Ciências
Subjects: oscillations [stars], Física [Ciências exactas e naturais], FOS: Physical sciences, Astrophysics, Type (model theory), Star (graph theory), stars: interiors, 01 natural sciences, Kepler, Spectral line, Physical sciences [Natural sciences], Astrophysics, Astronomy, Physical sciences, Physical sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrofísica, Astronomia, Ciências Físicas, Física, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, interiors [stars], 010308 nuclear & particles physics, Oscillation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], stars: late-type, Astronomy and Astrophysics, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, late-type [stars], Astrophysics::Earth and Planetary Astrophysics, stars: oscillations
Abstract: We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: About 20 modes of oscillation may be clearly distinguished in each star. We discuss the appearance of the oscillation spectra, use the frequencies and frequency separations to provide first results on the radii, masses and ages of the stars, and comment in the light of these results on prospects for inference on other solar-type stars that Kepler will observe., Comment: 16 pages, 3 figures, 1 table; now accepted for publication in ApJ Letters
Published: 2010

28. Asteroseismology of red-clump stars with CoRoT and Kepler

Author: A. Miglio, J. Montalbán, P. Eggenberger, S. Hekker, A. Noels, Joyce Ann Guzik, and Paul A. Bradley
Subjects: Physics, education.field_of_study, Star formation, Metallicity, Population, FOS: Physical sciences, Astrophysics, Radius, Astrophysics::Cosmology and Extragalactic Astrophysics, Kepler, Asteroseismology, Astrophysics - Astrophysics of Galaxies, Stars, Astrophysics - Solar and Stellar Astrophysics, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, education, Red clump, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics
Abstract: The availability of asteroseismic constraints for a large number of red giants with CoRoT and in the near future with Kepler, paves the way for detailed studies of populations of galactic-disk red giants. We investigate which information on the observed population can be recovered by the distribution of the observed seismic constraints: the frequency of maximum power of solar-like oscillations ($\nu_{max}$) and the large frequency separation ($\Delta\nu$). We use the distribution of $\nu_{max}$ and of $\Delta\nu$ observed by CoRoT in nearly 800 red giants in the first long observational run, as a tool to investigate the properties of galactic red-giant stars through the comparison with simulated distributions based on synthetic stellar populations. We can clearly identify the bulk of the red giants observed by CoRoT as red-clump stars, i.e. post-flash core-He-burning stars. The distribution of $\nu_{max}$ and of $\Delta\nu$ give us access to the distribution of the stellar radius and mass, and thus represent a most promising probe of the age and star formation rate of the disk, and of the mass-loss rate during the red-giant branch. This approach will be of great utility also in the interpretation of forthcoming surveys of variability of red giants with CoRoT and Kepler. In particular, an asteroseismic mass estimate of clump stars in the old-open clusters observed by Kepler, would represent a most valuable observational test of the poorly known mass-loss rate on the giant branch, and of its dependence on metallicity., Comment: 5 pages, 6 figures, proceeding for "Stellar Pulsation: Challenges for Theory and Observation", Santa Fe 2009
Published: 2009

29. The red-giant CoRoT target HR 7349

Author: F. Carrier, T. Morel, A. Miglio, J. Montalbán, M. Auvergne, A. Baglin, F. Baudin, C. Barban, C. Catala, F. D’Antona, J. De Ridder, P. Eggenberger, A. P. Hatzes, S. Hekker, T. Kallinger, E. Michel, A. Noels, E. Poretti, M. Rainer, R. Samadi, P. Ventura, and W. W. Weiss
Published: 2009

30. Red Giants observed with CoRoT

Author: S. Hekker, J. De Ridded, F. Baudin, C. Barban, F. Carrier, A. P. Hatzes, T. Kallinger, W. W. Weiss, Joyce Ann Guzik, and Paul A. Bradley
Subjects: Physics, Bright giant, K-type main-sequence star, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Giant star, Asteroseismology, Photometry (optics), Stars, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar-like oscillations, Variable star, Astrophysics::Galaxy Astrophysics
Abstract: Observations of red (G−K)‐giant stars with the CoRoT satellite provide unprecedented information on the stochastically excited oscillations in these stars. The long time series of nearly uninterrupted high‐cadence and high‐precision photometry revealed the presence of non‐radial modes with long lifetimes, which opens the possibility to perform asteroseismology on these stars. Also, the large number of red giants, for which solar‐like oscillations are now observed, allows for a more statistical investigation of the characteristics of solar‐like oscillations in red giants.
Published: 2009

31. Seismic analysis of HD 43587Aa, a solar-like oscillator in a multiple system

Author: T. Stahn, S. Mathur, R. Samadi, S. Hekker, Laurent Gizon, T. Appourchaux, Yveline Lebreton, C. Catala, Patrick Gaulme, Othman Benomar, M. Hall, P. Boumier, Ian W. Roxburgh, Clara Régulo, Graham A. Verner, E. Poretti, B. Mosser, T. Morel, A. Baglin, F. Baudin, J. D. do Nascimento, D. Salabert, M. Auvergne, R. A. Garcia, E. Michel, William J. Chaplin, Yvonne Elsworth, M. Rainer, S. Chaintreuil, Low Energy Astrophysics (API, FNWI), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), School of Physics and Astronomy, University of Birmingham [Birmingham], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Insituto Geofísico, Escuela Politécnica Nacional (EPN), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université de Liège, INAF - Osservatorio Astronomico di Brera (OAB), Istituto Nazionale di Astrofisica (INAF), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, stars: individual: HD 43587Aa, FOS: Physical sciences, Orbital eccentricity, Astrophysics, asteroseismology, Star (graph theory), stars, HD 43587Aa, binaries, solar-type, data analysis, Rotation, 01 natural sciences, Apparent magnitude, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, Astronomy and Astrophysics, stars: solar-type, Radius, Effective temperature, methods: data analysis, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Radial velocity, binaries: general, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Context. The object HD 43587Aa is a G0V star observed during the 145-day LRa03 run of the COnvection, ROtation and planetary Transits space mission (CoRoT), for which complementary High Accuracy Radial velocity Planet Searcher (HARPS) spectra with S/N > 300 were also obtained. Its visual magnitude is 5.71, and its effective temperature is close to 5950 K. It has a known companion in a highly eccentric orbit and is also coupled with two more distant companions.Aims. We undertake a preliminary investigation of the internal structure of HD 43587Aa.Methods. We carried out a seismic analysis of the star, using maximum likelihood estimators and Markov chain Monte Carlo methods.Results. We established the first table of the eigenmode frequencies, widths, and heights for HD 43587Aa. The star appears to have a mass and a radius slightly larger than the Sun, and is slightly older (5.6 Gyr). Two scenarios are suggested for the geometry of the star: either its inclination angle is very low, or the rotation velocity of the star is very low.Conclusions. A more detailed study of the rotation and of the magnetic and chromospheric activity for this star is needed, and will be the subject of a further study. New high resolution spectrometric observations should be performed for at least several months in duration.
Published: 2014

32. KIC 2568888: To Be or Not to Be a Binary.

Author: N. Themessl, S. Hekker, A. Mints, R. A. García, A. García Saravia Ortiz de Montellano, P. B. Stetson, and J. De Ridder
Subjects: *BINARY stars, *GIANT stars, *ASTRONOMICAL photometry, *SEISMOLOGY, *POWER density
Abstract: In cases where both components of a binary system show oscillations, asteroseismology has been proposed as a method to identify the system. For KIC 2568888, observed with Kepler, we detect oscillation modes for two red giants in a single power-density spectrum. Through an asteroseismic study we investigate if the stars have similar properties, which could be an indication that they are physically bound into a binary system. While one star lies on the red giant branch (RGB), the other, more evolved star, is either a RGB or asymptotic giant branch star. We found similar ages for the red giants and a mass ratio close to 1. Based on these asteroseismic results, we propose KIC 2568888 as a rare candidate binary system (∼0.1% chance). However, when combining the asteroseismic data with ground-based BVI photometry we estimated different distances for the stars, which we cross-checked with Gaia DR2. From Gaia we obtained for one object a distance between and broadly consistent with the distances from BVI photometry. For the other object we have a negative parallax with a not yet reliable Gaia distance solution. The derived distances challenge a binary interpretation and may either point to a triple system, which could explain the visible magnitudes, or, to a rare chance alignment (∼0.05% chance based on stellar magnitudes). This probability would even be smaller, if calculated for close pairs of stars with a mass ratio close to unity in addition to similar magnitudes, which may indeed indicate that a binary scenario is more favorable. [ABSTRACT FROM AUTHOR]
Published: 2018
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33. Improved asteroseismic inversions for red-giant surface rotation rates

Author: F. Ahlborn, E. P. Bellinger, S. Hekker, S. Basu, and D. Mokrytska
Subjects: rotation [Stars], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, oscillations [Stars], Asteroseismology, interiors [Stars], FOS: Physical sciences, Astronomy and Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: Asteroseismic observations of internal stellar rotation have indicated a substantial lack of angular momentum transport in theoretical models of subgiant and red-giant stars. Accurate core and surface rotation rate measurements are therefore needed to constrain internal transport processes included in the models. We eliminate substantial systematic errors of asteroseismic surface rotation rates found in previous studies. We propose a new objective function for the Optimally Localized Averages method of rotational inversions for red-giant stars, which results in more accurate envelope rotation rate estimates obtained from the same data. We use synthetic observations from stellar models across a range of evolutionary stages and masses to demonstrate the improvement. We find that our new inversion technique allows us to obtain estimates of the surface rotation rate that are independent of the core rotation. For a star at the base of the red-giant branch, we reduce the systematic error from about 20% to a value close to 0, assuming constant envelope rotation. We also show the equivalence between this method and the method of linearised rotational splittings. Our new rotational inversion method substantially reduces the systematic errors of red-giant surface rotation rates. In combination with independent measures of the surface rotation rate, this will allow better constraints to be set on the internal rotation profile. This will be a very important probe to further constrain the internal angular momentum transport along the lower part of the red-giant branch., 17 pages, 22 figures, accepted for publication in Astronomy and Astrophysics
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34. SPIN–ORBIT ALIGNMENT OF EXOPLANET SYSTEMS: ENSEMBLE ANALYSIS USING ASTEROSEISMOLOGY.

Author: T. L. Campante, M. N. Lund, J. S. Kuszlewicz, G. R. Davies, W. J. Chaplin, S. Albrecht, J. N. Winn, T. R. Bedding, O. Benomar, D. Bossini, R. Handberg, A. R. G. Santos, V. Van Eylen, S. Basu, J. Christensen-Dalsgaard, Y. P. Elsworth, S. Hekker, T. Hirano, D. Huber, and C. Karoff
Subjects: EXTRASOLAR planets, ORIGIN of planets, KEPLER'S laws, BAYESIAN analysis, BAYES' theorem
Abstract: The angle ψ between a planet’s orbital axis and the spin axis of its parent star is an important diagnostic of planet formation, migration, and tidal evolution. We seek empirical constraints on ψ by measuring the stellar inclination is via asteroseismology for an ensemble of 25 solar-type hosts observed with NASA’s Kepler satellite. Our results for is are consistent with alignment at the 2σ level for all stars in the sample, meaning that the system surrounding the red-giant star Kepler-56 remains as the only unambiguous misaligned multiple-planet system detected to date. The availability of a measurement of the projected spin–orbit angle λ for two of the systems allows us to estimate ψ. We find that the orbit of the hot Jupiter HAT-P-7b is likely to be retrograde (), whereas that of Kepler-25c seems to be well aligned with the stellar spin axis (). While the latter result is in apparent contradiction with a statement made previously in the literature that the multi-transiting system Kepler-25 is misaligned, we show that the results are consistent, given the large associated uncertainties. Finally, we perform a hierarchical Bayesian analysis based on the asteroseismic sample in order to recover the underlying distribution of ψ. The ensemble analysis suggests that the directions of the stellar spin and planetary orbital axes are correlated, as conveyed by a tendency of the host stars to display large values of inclination. [ABSTRACT FROM AUTHOR]
Published: 2016
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35. INTERNAL ROTATION OF THE RED-GIANT STAR KIC 4448777 BY MEANS OF ASTEROSEISMIC INVERSION.

Author: M. P. Di Mauro, R. Ventura, D. Cardini, D. Stello, J. Christensen-Dalsgaard, W. A. Dziembowski, L. Paternò, P. G. Beck, S. Bloemen, G. R. Davies, K. De Smedt, Y. Elsworth, R. A. García, S. Hekker, B. Mosser, and A. Tkachenko
Subjects: ASYMPTOTIC giant branch stars, STELLAR structure, RED giants, STELLAR oscillations, STELLAR rotation, STELLAR evolution
Abstract: We study the dynamics of the stellar interior of the early red-giant star KIC 4448777 by asteroseismic inversion of 14 splittings of the dipole mixed modes obtained from Kepler observations. In order to overcome the complexity of the oscillation pattern typical of red-giant stars, we present a procedure to extract the rotational splittings from the power spectrum. We find not only that the core rotates from a minimum of 8 to a maximum of 17 times faster than the surface, confirming previous inversion results generated for other red giants (Deheuvels et al.), but we also estimate the variation of the angular velocity within the helium core with a spatial resolution of 0.001R and verify the hypothesis of a sharp discontinuity in the inner stellar rotation. The results show that the entire core rotates rigidly and provide evidence for an angular velocity gradient around the base of the hydrogen-burning shell; however, we do not succeed in characterizing the rotational slope, due to the intrinsic limits of the applied techniques. The angular velocity, from the edge of the core, appears to decrease with increasing distance from the center, reaching an average value in the convective envelope of 68 ± 22 nHz. We conclude that a set of data that includes only dipolar modes is sufficient to infer quite accurately the rotation of a red giant not only in the dense core but also, with a lower level of confidence, in part of the radiative region and in the convective envelope. [ABSTRACT FROM AUTHOR]
Published: 2016
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36. Hot super-Earths stripped by their host stars.

Author: Lundkvist MS, Kjeldsen H, Albrecht S, Davies GR, Basu S, Huber D, Justesen AB, Karoff C, Silva Aguirre V, Van Eylen V, Vang C, Arentoft T, Barclay T, Bedding TR, Campante TL, Chaplin WJ, Christensen-Dalsgaard J, Elsworth YP, Gilliland RL, Handberg R, Hekker S, Kawaler SD, Lund MN, Metcalfe TS, Miglio A, Rowe JF, Stello D, Tingley B, and White TR
Abstract: Simulations predict that hot super-Earth sized exoplanets can have their envelopes stripped by photoevaporation, which would present itself as a lack of these exoplanets. However, this absence in the exoplanet population has escaped a firm detection. Here we demonstrate, using asteroseismology on a sample of exoplanets and exoplanet candidates observed during the Kepler mission that, while there is an abundance of super-Earth sized exoplanets with low incident fluxes, none are found with high incident fluxes. We do not find any exoplanets with radii between 2.2 and 3.8 Earth radii with incident flux above 650 times the incident flux on Earth. This gap in the population of exoplanets is explained by evaporation of volatile elements and thus supports the predictions. The confirmation of a hot-super-Earth desert caused by evaporation will add an important constraint on simulations of planetary systems, since they must be able to reproduce the dearth of close-in super-Earths.
Published: 2016
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37. Precise stellar surface gravities from the time scales of convectively driven brightness variations.

Author: Kallinger T, Hekker S, García RA, Huber D, and Matthews JM
Subjects: Extraterrestrial Environment, Astronomy methods, Gravitation, Stars, Celestial
Abstract: A significant part of the intrinsic brightness variations in cool stars of low and intermediate mass arises from surface convection (seen as granulation) and acoustic oscillations (p-mode pulsations). The characteristics of these phenomena are largely determined by the stars' surface gravity (g). Detailed photometric measurements of either signal can yield an accurate value of g. However, even with ultraprecise photometry from NASA's Kepler mission, many stars are too faint for current methods or only moderate accuracy can be achieved in a limited range of stellar evolutionary stages. This means that many of the stars in the Kepler sample, including exoplanet hosts, are not sufficiently characterized to fully describe the sample and exoplanet properties. We present a novel way to measure surface gravities with accuracies of about 4%. Our technique exploits the tight relation between g and the characteristic time scale of the combined granulation and p-mode oscillation signal. It is applicable to all stars with a convective envelope, including active stars. It can measure g in stars for which no other analysis is now possible. Because it depends on the time scale (and no other properties) of the signal, our technique is largely independent of the type of measurement (for example, photometry or radial velocity measurements) and the calibration of the instrumentation used. However, the oscillation signal must be temporally resolved; thus, it cannot be applied to dwarf stars observed by Kepler in its long-cadence mode.
Published: 2016
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38. Stellar spin-orbit misalignment in a multiplanet system.

Author: Huber D, Carter JA, Barbieri M, Miglio A, Deck KM, Fabrycky DC, Montet BT, Buchhave LA, Chaplin WJ, Hekker S, Montalbán J, Sanchis-Ojeda R, Basu S, Bedding TR, Campante TL, Christensen-Dalsgaard J, Elsworth YP, Stello D, Arentoft T, Ford EB, Gilliland RL, Handberg R, Howard AW, Isaacson H, Johnson JA, Karoff C, Kawaler SD, Kjeldsen H, Latham DW, Lund MN, Lundkvist M, Marcy GW, Metcalfe TS, Silva Aguirre V, and Winn JN
Abstract: Stars hosting hot Jupiters are often observed to have high obliquities, whereas stars with multiple coplanar planets have been seen to have low obliquities. This has been interpreted as evidence that hot-Jupiter formation is linked to dynamical disruption, as opposed to planet migration through a protoplanetary disk. We used asteroseismology to measure a large obliquity for Kepler-56, a red giant star hosting two transiting coplanar planets. These observations show that spin-orbit misalignments are not confined to hot-Jupiter systems. Misalignments in a broader class of systems had been predicted as a consequence of torques from wide-orbiting companions, and indeed radial velocity measurements revealed a third companion in a wide orbit in the Kepler-56 system.
Published: 2013
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39. A sub-Mercury-sized exoplanet.

Author: Barclay T, Rowe JF, Lissauer JJ, Huber D, Fressin F, Howell SB, Bryson ST, Chaplin WJ, Désert JM, Lopez ED, Marcy GW, Mullally F, Ragozzine D, Torres G, Adams ER, Agol E, Barrado D, Basu S, Bedding TR, Buchhave LA, Charbonneau D, Christiansen JL, Christensen-Dalsgaard J, Ciardi D, Cochran WD, Dupree AK, Elsworth Y, Everett M, Fischer DA, Ford EB, Fortney JJ, Geary JC, Haas MR, Handberg R, Hekker S, Henze CE, Horch E, Howard AW, Hunter RC, Isaacson H, Jenkins JM, Karoff C, Kawaler SD, Kjeldsen H, Klaus TC, Latham DW, Li J, Lillo-Box J, Lund MN, Lundkvist M, Metcalfe TS, Miglio A, Morris RL, Quintana EV, Stello D, Smith JC, Still M, and Thompson SE
Abstract: Since the discovery of the first exoplanets, it has been known that other planetary systems can look quite unlike our own. Until fairly recently, we have been able to probe only the upper range of the planet size distribution, and, since last year, to detect planets that are the size of Earth or somewhat smaller. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.
Published: 2013
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40. Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.

Author: Carter JA, Agol E, Chaplin WJ, Basu S, Bedding TR, Buchhave LA, Christensen-Dalsgaard J, Deck KM, Elsworth Y, Fabrycky DC, Ford EB, Fortney JJ, Hale SJ, Handberg R, Hekker S, Holman MJ, Huber D, Karoff C, Kawaler SD, Kjeldsen H, Lissauer JJ, Lopez ED, Lund MN, Lundkvist M, Metcalfe TS, Miglio A, Rogers LA, Stello D, Borucki WJ, Bryson S, Christiansen JL, Cochran WD, Geary JC, Gilliland RL, Haas MR, Hall J, Howard AW, Jenkins JM, Klaus T, Koch DG, Latham DW, MacQueen PJ, Sasselov D, Steffen JH, Twicken JD, and Winn JN
Abstract: In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.
Published: 2012
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41. Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes.

Author: Beck PG, Montalban J, Kallinger T, De Ridder J, Aerts C, García RA, Hekker S, Dupret MA, Mosser B, Eggenberger P, Stello D, Elsworth Y, Frandsen S, Carrier F, Hillen M, Gruberbauer M, Christensen-Dalsgaard J, Miglio A, Valentini M, Bedding TR, Kjeldsen H, Girouard FR, Hall JR, and Ibrahim KA
Abstract: When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected 'mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior.
Published: 2011
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42. Kepler detected gravity-mode period spacings in a red giant star.

Author: Beck PG, Bedding TR, Mosser B, Stello D, Garcia RA, Kallinger T, Hekker S, Elsworth Y, Frandsen S, Carrier F, De Ridder J, Aerts C, White TR, Huber D, Dupret MA, Montalbán J, Miglio A, Noels A, Chaplin WJ, Kjeldsen H, Christensen-Dalsgaard J, Gilliland RL, Brown TM, Kawaler SD, Mathur S, and Jenkins JM
Abstract: Stellar interiors are inaccessible through direct observations. For this reason, helioseismologists made use of the Sun's acoustic oscillation modes to tune models of its structure. The quest to detect modes that probe the solar core has been ongoing for decades. We report the detection of mixed modes penetrating all the way to the core of an evolved star from 320 days of observations with the Kepler satellite. The period spacings of these mixed modes are directly dependent on the density gradient between the core region and the convective envelope.
Published: 2011
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43. Ensemble asteroseismology of solar-type stars with the NASA Kepler mission.

Author: Chaplin WJ, Kjeldsen H, Christensen-Dalsgaard J, Basu S, Miglio A, Appourchaux T, Bedding TR, Elsworth Y, García RA, Gilliland RL, Girardi L, Houdek G, Karoff C, Kawaler SD, Metcalfe TS, Molenda-Żakowicz J, Monteiro MJ, Thompson MJ, Verner GA, Ballot J, Bonanno A, Brandão IM, Broomhall AM, Bruntt H, Campante TL, Corsaro E, Creevey OL, Doğan G, Esch L, Gai N, Gaulme P, Hale SJ, Handberg R, Hekker S, Huber D, Jiménez A, Mathur S, Mazumdar A, Mosser B, New R, Pinsonneault MH, Pricopi D, Quirion PO, Régulo C, Salabert D, Serenelli AM, Silva Aguirre V, Sousa SG, Stello D, Stevens IR, Suran MD, Uytterhoeven K, White TR, Borucki WJ, Brown TM, Jenkins JM, Kinemuchi K, Van Cleve J, and Klaus TC
Abstract: In addition to its search for extrasolar planets, the NASA Kepler mission provides exquisite data on stellar oscillations. We report the detections of oscillations in 500 solar-type stars in the Kepler field of view, an ensemble that is large enough to allow statistical studies of intrinsic stellar properties (such as mass, radius, and age) and to test theories of stellar evolution. We find that the distribution of observed masses of these stars shows intriguing differences to predictions from models of synthetic stellar populations in the Galaxy.
Published: 2011
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44. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars.

Author: Bedding TR, Mosser B, Huber D, Montalbán J, Beck P, Christensen-Dalsgaard J, Elsworth YP, García RA, Miglio A, Stello D, White TR, De Ridder J, Hekker S, Aerts C, Barban C, Belkacem K, Broomhall AM, Brown TM, Buzasi DL, Carrier F, Chaplin WJ, Di Mauro MP, Dupret MA, Frandsen S, Gilliland RL, Goupil MJ, Jenkins JM, Kallinger T, Kawaler S, Kjeldsen H, Mathur S, Noels A, Aguirre VS, and Ventura P
Abstract: 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 ∼ 50 seconds) and those that are also burning helium (period spacing ∼ 100 to 300 seconds).
Published: 2011
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45. Non-radial oscillation modes with long lifetimes in giant stars.

Author: De Ridder J, Barban C, Baudin F, Carrier F, Hatzes AP, Hekker S, Kallinger T, Weiss WW, Baglin A, Auvergne M, Samadi R, Barge P, and Deleuil M
Abstract: Towards the end of their lives, stars like the Sun greatly expand to become red giant stars. Such evolved stars could provide stringent tests of stellar theory, as many uncertainties of the internal stellar structure accumulate with age. Important examples are convective overshooting and rotational mixing during the central hydrogen-burning phase, which determine the mass of the helium core, but which are not well understood. In principle, analysis of radial and non-radial stellar oscillations can be used to constrain the mass of the helium core. Although all giants are expected to oscillate, it has hitherto been unclear whether non-radial modes are observable at all in red giants, or whether the oscillation modes have a short or a long mode lifetime, which determines the observational precision of the frequencies. Here we report the presence of radial and non-radial oscillations in more than 300 giant stars. For at least some of the giants, the mode lifetimes are of the order of a month. We observe giant stars with equally spaced frequency peaks in the Fourier spectrum of the time series, as well as giants for which the spectrum seems to be more complex. No satisfactory theoretical explanation currently exists for our observations.
Published: 2009
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