Search

Your search keyword '"J. Christensen‐Dalsgaard"' showing total 212 results
Start Over Author "J. Christensen‐Dalsgaard"
212 results on '"J. Christensen‐Dalsgaard"'

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
Full Text
View/download PDF

3. First Results on RR Lyrae Stars with the TESS Space Telescope: Untangling the Connections between Mode Content, Colors, and Distances

Author

L. Molnár, A. Bódi, A. Pál, A. Bhardwaj, F–J. Hambsch, J. M. Benkő, A. Derekas, M. Ebadi, M. Joyce, A. Hasanzadeh, K. Kolenberg, M. B. Lund, J. M. Nemec, H. Netzel, C. –C. Ngeow, J. Pepper, E. Plachy, Z. Prudil, R. J. Siverd, M. Skarka, R. Smolec, Á. Sódor, S. Sylla, P. Szabó, R. Szabó, H. Kjeldsen, J. Christensen-Dalsgaard, and G. R. Ricker

Published
2021
Full Text
View/download PDF

4. Evolution of dipolar mixed-mode coupling factor in red giant stars: impact of buoyancy spike

Author

C Jiang, M Cunha, J Christensen-Dalsgaard, Q S Zhang, and L Gizon

Subjects
interiors [stars], oscillations [stars], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, evolution [stars], FOS: Physical sciences, Astronomy and Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

Mixed modes observed in red giants allow for investigation of the stellar interior structures. One important feature in these structures is the buoyancy spike caused by the discontinuity of the chemical gradient left behind during the first dredge-up. The buoyancy spike emerges at the base of the convective zone in low-luminosity red giants and later becomes a glitch when the g-mode cavity expands to encompass the spike. Here, we study the impact of the buoyancy spike on the dipolar mixed modes using stellar models with different properties. We find that the applicability of the asymptotic formalisms for the coupling factor, q, varies depending on the location of the evanescent zone, relative to the position of the spike. Significant deviations between the value of q inferred from fitting the oscillation frequencies and either of the formalisms proposed in the literature are found in models with a large frequency separation in the interval 5 to 15 microHz, with evanescent zones located in a transition region which may be thin or thick. However, it is still possible to reconcile q with the predictions from the asymptotic formalisms, by choosing which formalism to use according to the value of q. For stars approaching the luminosity bump, the buoyancy spike becomes a glitch and strongly affects the mode frequencies. Fitting the frequencies without accounting for the glitch leads to unphysical variations in the inferred q, but we show that this is corrected when properly accounting for the glitch in the fitting., Comment: 21 pages, 10 figures

Published
2022

5. 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
Full Text
View/download PDF

6. First Results on RR Lyrae Stars with the TESS Space Telescope:Untangling the Connections between Mode Content, Colors, and Distances

Author

L. Molnár, A. Bódi, A. Pál, A. Bhardwaj, F–J. Hambsch, J. M. Benkő, A. Derekas, M. Ebadi, M. Joyce, A. Hasanzadeh, K. Kolenberg, M. B. Lund, J. M. Nemec, H. Netzel, C. –C. Ngeow, J. Pepper, E. Plachy, Z. Prudil, R. J. Siverd, M. Skarka, R. Smolec, Á. Sódor, S. Sylla, P. Szabó, R. Szabó, H. Kjeldsen, J. Christensen-Dalsgaard, G. R. Ricker, Molnár, L [0000-0002-8159-1599], Bódi, A [0000-0002-8585-4544], Pál, A [0000-0001-5449-2467], Bhardwaj, A [0000-0001-6147-3360], Benkő, JM [0000-0003-3851-6603], Derekas, A [0000-0002-6526-9444], Joyce, M [0000-0002-8717-127X], Hasanzadeh, A [0000-0002-7286-1438], Kolenberg, K [0000-0001-5181-5072], Lund, MB [0000-0003-2527-1598], Nemec, JM [0000-0003-1281-5525], Netzel, H [0000-0001-5608-0028], Ngeow, C–C [0000-0001-8771-7554], Pepper, J [0000-0002-3827-8417], Plachy, E [0000-0002-5481-3352], Prudil, Z [0000-0001-5497-5805], Siverd, RJ [0000-0001-5016-3359], Skarka, M [0000-0002-7602-0046], Smolec, R [0000-0001-7217-4884], Sódor, Á [0000-0001-7806-2883], Szabó, P [0000-0002-5781-1926], Szabó, R [0000-0002-3258-1909], Kjeldsen, H [0000-0002-9037-0018], Christensen-Dalsgaard, J [0000-0001-5137-0966], Ricker, GR [0000-0003-2058-6662], and Apollo - University of Cambridge Repository

Subjects
OGLE COLLECTION, GRAVITATIONAL LENSING EXPERIMENT, FOS: Physical sciences, 5109 Space Sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy & Astrophysics, GALACTIC BULGE, 01 natural sciences, FREQUENCY-ANALYSIS, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, HYDROGEN EMISSION, LIGHT CURVES, DOUBLE-PERIODIC PULSATION, Science & Technology, 010308 nuclear & particles physics, Physics, Astronomy and Astrophysics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 5101 Astronomical Sciences, Physical Sciences, EXTENDED APERTURE PHOTOMETRY, LARGE-MAGELLANIC-CLOUD, Astrophysics::Earth and Planetary Astrophysics, BLAZHKO MODULATION, 51 Physical Sciences
Abstract

The TESS space telescope is collecting continuous, high-precision optical photometry of stars throughout the sky, including thousands of RR Lyrae stars. In this paper, we present results for an initial sample of 118 nearby RR Lyrae stars observed in TESS Sectors 1 and 2. We use differential-image photometry to generate light curves and analyse their mode content and modulation properties. We combine accurate light curve parameters from TESS with parallax and color information from the Gaia mission to create a comprehensive classification scheme. We build a clean sample, preserving RR Lyrae stars with unusual light curve shapes, while separating other types of pulsating stars. We find that a large fraction of RR Lyrae stars exhibit various low-amplitude modes, but the distribution of those modes is markedly different from those of the bulge stars. This suggests that differences in physical parameters have an observable effect on the excitation of extra modes, potentially offering a way to uncover the origins of these signals. However, mode identification is hindered by uncertainties when identifying the true pulsation frequencies of the extra modes. We compare mode amplitude ratios in classical double-mode stars to stars with extra modes at low amplitudes and find that they separate into two distinct groups. Finally, we find a high percentage of modulated stars among the fundamental-mode pulsators, but also find that at least 28% of them do not exhibit modulation, confirming that a significant fraction of stars lack the Blazhko effect., 35 pages, 26 figures, and a 19-page appendix. Accepted for publication in ApJS. Light curve data temporarily available: https://konkoly.hu/staff/lmolnar/tess_rrl_firstlight_all_lcs.txt

Published
2022

7. Update on Global Helioseismic Observations of the Solar Torsional Oscillation

Author

Rachel Howe, W. J. Chaplin, J. Christensen-Dalsgaard, Y. P. Elsworth, and J. Schou

Subjects
General Medicine
Abstract

We present an up-to-date latitude–time map of the solar zonal flows at 0.99 R ⊙ from global helioseismology using data from the Global Oscillation Network Group, the Michelson Doppler Imager, and the Helioseismic and Magnetic Imager.

Published
2022

8. Is human underwater hearing mediated by bone conduction?

Author

K. Sørensen, J. Christensen-Dalsgaard, and M. Wahlberg

Subjects
Sound conduction, Acoustic Stimulation, Hearing, Hearing Tests, otorhinolaryngologic diseases, Ear, Middle, Humans, Water, Auditory Threshold, Underwater hearing, Bone Conduction, Sound localization, Sensory Systems
Abstract

In-air and underwater audiograms and directional hearing abilities were measured in humans. The lowest underwater thresholds were 2.8 µW/m2 or 3.6 mPa at a frequency of 500 Hz. The underwater hearing thresholds were 4–26 dB and 40–62 dB higher than in-air hearing thresholds when measured in intensity and pressure units, respectively. This difference is considerably smaller than what has been reported earlier. At frequencies below 1 kHz, when measured in units of particle velocity, the underwater threshold was much lower than published bone conduction thresholds, suggesting that underwater hearing is not always mediated by bone conduction pathways to the inner ear, as previously thought. We suggest it is the resonance of air in the air-filled middle ear that produces the low underwater thresholds, at least at frequencies below 1 kHz. The ability to determine the direction of a 700 Hz underwater sound source while being blindfolded was extremely poor, with submerged test subjects showing only coarse directional hearing abilities at azimuths of less than 50˚. The physical cues to sound direction are different in air and water, and the poor directional hearing abilities indicate that, in spite of low hearing thresholds, humans have no special adaptations to process directional acoustic cues under water.

Published
2021

9. Erratum:Variations of the mixing character of dipolar mixed modes in red giant stars

Author

Q. S. Zhang, J. Christensen-Dalsgaard, Chen Jiang, and M. S. Cunha

Subjects
Physics, Dipole, Stars, Character (mathematics), Space and Planetary Science, Red giant, Astronomy and Astrophysics, Astrophysics, Asteroseismology, Mixing (physics)
Abstract

The paper Variations of the mixing character of dipolar mixed modes in red giant stars was published inMNRAS 495, 621-636 (2020). There are a few corrections that we would like to make in this erratum. Firstly, in the original version of this manuscript, there was a typographical error in last author QS. Zhang s name. This has now been corrected as Q. S. Zhang. Secondly, we mislabelled the ordinate of Fig. (Figure Presented).

Published
2020

10. 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
Full Text
View/download PDF

11. No swan song for Sun-as-a-star helioseismology: Performances of the Solar-SONG prototype for individual mode characterisation

Author

Frank Grundahl, J. Christensen-Dalsgaard, R. A. Garcia, S. N. Breton, H. Kjeldsen, Pere L. Palle, S. Mathur, M. Fredslund Andersen, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / 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-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Instituto de Astrofisica de Canarias (IAC), Universidad de La Laguna [Tenerife - SP] (ULL), and Aarhus University [Aarhus]

Subjects
Physics, Mode (statistics), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, methods: data analysis, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, helioseismology [Sun], Helioseismology, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], data analysis [Methods], Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), Sun: helioseismology
Abstract

The GOLF instrument on board SoHO has been in operation for almost 25 years but aging of the instrument has now strongly affected its performance, especially in the low-frequency p-mode region. At the end of the SoHO mission, the ground-based network BiSON will remain the only facility able to perform Sun-integrated helioseismic observations. Therefore, we want to assess the helioseismic performances of an \'echelle spectrograph like SONG. Indeed, the high precision of such an instrument and the quality of the data acquired for asteroseismic purpose calls for an evaluation of the instrument ability to perform global radial-velocity measurements of the solar disk. Data acquired during the Solar-SONG 2018 observation campaign at the Teide Observatory are used to study mid- and low-frequency p modes. A Solar-SONG time series of 30-day duration is reduced with a combination of the traditional IDL iSONG pipeline and a new Python pipeline described in this paper. A mode fitting method built around a Bayesian approach is then performed on the Solar-SONG and contemporaneous GOLF, BiSON, and HMI data. For this contemporaneous time series, Solar-SONG is able to characterise p modes at a lower frequency than BiSON and GOLF (1750{\mu}Hz against 1946 and 2157 {\mu}Hz respectively), while for HMI it is possible to characterise a mode at 1686 {\mu}Hz. The decrease of GOLF sensitivity is then evaluated through the evolution of its low-frequency p-mode characterisation abilities over the years. [abridged], Comment: 24 pages, 17 figures. Accepted in A&A

Published
2022

12. The Asteroseismic Target List (ATL) for solar-like oscillators observed in 2-minute cadence with the Transiting Exoplanet Survey Satellite (TESS)

Author

V. Silva Aguirre, O. L. Creevey, T. L. Campante, J. Christensen-Dalsgaard, D. W. Latham, M. N. Lund, T. S. Metcalfe, H. Kjeldsen, Rasmus Handberg, S. Basu, T. Appourchaux, Warrick H. Ball, R. Vanderspek, George R. Ricker, Timothy R. Bedding, Andrea Miglio, Daniel Huber, William J. Chaplin, Rafael A. García, S. D. Kawaler, A. M. Serenelli, Guy R. Davies, D. Stello, Mathew Schofield, Department of Psychology, St John's University, 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), Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, 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 Astronomy, Yale University [New Haven], Sydney Institute for Astronomy (SIfA), The University of Sydney, Danish AsteroSeismology Centre (DASC), Aarhus University [Aarhus], 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), Research institute of Computer Vision and Robotics [Girona] (VICOROB), Universitat de Girona (UdG), Department of Physics and Astronomy [Aarhus], Department of Physics and Astronomy [Iowa City], and University of Iowa [Iowa City]

Subjects
oscillations [stars], Source code, instruments [space vehicles], media_common.quotation_subject, fundamental parameters [stars], FOS: Physical sciences, Astrophysics, 01 natural sciences, Asteroseismology, surveys, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), media_common, Physics, 010308 nuclear & particles physics, Subgiant, Astronomy and Astrophysics, Exoplanet, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Satellite, Cadence, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], catalogs
Abstract

We present the target list of solar-type stars to be observed in short-cadence (2-min) for asteroseismology by the NASA Transiting Exoplanet Survey Satellite (TESS) during its 2-year nominal survey mission. The solar-like Asteroseismic Target List (ATL) is comprised of bright, cool main-sequence and subgiant stars and forms part of the larger target list of the TESS Asteroseismic Science Consortium (TASC). The ATL uses Gaia DR2 and the Extended Hipparcos Compilation (XHIP) to derive fundamental stellar properties, calculate detection probabilities and produce a rank-ordered target list. We provide a detailed description of how the ATL was produced and calculate expected yields for solar-like oscillators based on the nominal photometric performance by TESS. We also provide publicly available source code which can be used to reproduce the ATL, thereby enabling comparisons of asteroseismic results from TESS with predictions from synthetic stellar populations., Comment: 13 pages, 11 figures; accepted for publication in Astrophysical Journal Supplement Series

Published
2019
Full Text
View/download PDF

13. 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

14. Fourier analysis of non-Blazhko ab-type RR Lyrae stars observed with the Kepler space telescope

Author

J. M. Nemec, R. Smolec, J. M. Benkő, P. Moskalik, K. Kolenberg, R. Szabó, D. W. Kurtz, S. Bryson, E. Guggenberger, M. Chadid, Y.-B. Jeon, A. Kunder, A. C. Layden, K. Kinemuchi, L. L. Kiss, E. Poretti, J. Christensen-Dalsgaard, H. Kjeldsen, D. Caldwell, V. Ripepi, A. Derekas, J. Nuspl, F. Mullally, S. E. Thompson, and W. J. Borucki

Subjects
Physics, 010308 nuclear & particles physics, Blazhko effect, Astronomy and Astrophysics, Astrophysics, RR Lyrae variable, 01 natural sciences, Stars, Photometry (astronomy), symbols.namesake, Spitzer Space Telescope, Space and Planetary Science, Fourier analysis, 0103 physical sciences, symbols, 010303 astronomy & astrophysics, Stellar evolution, Fourier series
Abstract

Nineteen of the ~40 RR Lyr stars in the Kepler field have been identified as candidate non-Blazhko (or unmodulated) stars. In this paper we present the results of Fourier decomposition of the time-series photometry of these stars acquired during the first 417 days of operation (Q0-Q5) of the Kepler telescope. Fourier parameters based on ~18400 long-cadence observations per star (and ~150000 short-cadence observations for FN Lyr and for AW Dra) are derived. None of the stars shows the recently discovered `period-doubling' effect seen in Blazhko variables; however, KIC 7021124 has been found to pulsate simultaneously in the fundamental and second overtone modes with a period ratio P2/P0 ~ 0.59305 and is similar to the double-mode star V350 Lyr. Period change rates are derived from O-C diagrams spanning, in some cases, over 100 years; these are compared with high-precision periods derived from the Kepler data alone. Extant Fourier correlations by Kovacs, Jurcsik et al. (with minor transformations from the V to the Kp passband) have been used to derive underlying physical characteristics for all the stars. This procedure seems to be validated through comparisons of the Kepler variables with galactic and LMC RR Lyr stars. The most metal-poor star in the sample is NR Lyr, with [Fe/H]=-2.3 dex; and the four most metal-rich stars have [Fe/H] ranging from -0.6 to +0.1 dex. Pulsational luminosities and masses are found to be systematically smaller than L and mass values derived from stellar evolution models, and are favoured over the evolutionary values when periods are computed with the Warsaw linear hydrodynamics code. Finally, the Fourier parameters are compared with theoretical values derived using the Warsaw non-linear convective pulsation code.

Published
2011

15. The excitation of solar-like oscillations in a δ Sct star by efficient envelope convection

Author

Tiago L. Campante, Antonio Frasca, J. Christensen-Dalsgaard, Theresa Lüftinger, Thomas Kallinger, Dennis Stello, Christopher Allen, J. Van Cleve, P. Lenz, D. W. Kurtz, A. Moya, Andreas Kaiser, Giovanni Catanzaro, Gerald Handler, A. Grigahcène, Hans Kjeldsen, Victoria Antoci, T. R. Bedding, P. De Cat, G. Houdek, H. Bruntt, A. O. Thygesen, K. Uytterhoeven, Bruce D. Clarke, Institute for Astronomy [Vienna], University of Vienna [Vienna], Copernicus Astronomical Center of the Polish Academy of Sciences (CAMK), Polish Academy of Sciences (PAN), Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto = University of Porto, Department of Physics and Astronomy [Aarhus], Aarhus University [Aarhus], Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Sydney Institute for Astronomy (SIfA), The University of Sydney, INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), Solar Influences Data Analysis Center [Brussels] (SIDC), Royal Observatory of Belgium [Brussels] (ROB), 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), Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy [Preston], University of Central Lancashire [Preston] (UCLAN), Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN), Centrale Lille-Institut supérieur de l'électronique et du numérique (ISEN)-Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF), SETI Institute, NASA Ames Research Center (ARC), Universidade do Porto, Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA), 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), Universidade do Porto [Porto], Departamento de Astrofísica [Madrid], Consejo Superior de Investigaciones Científicas [Spain] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC)-Instituto Nacional de Técnica Aeroespacial (INTA), Royal Observatory of Belgium [Brussels], Institut d’Électronique, de Microélectronique et de Nanotechnologie (IEMN) - UMR 8520 (IEMN), and Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Université Polytechnique Hauts-de-France (UPHF)-Ecole Centrale de Lille-Université Polytechnique Hauts-de-France (UPHF)-Institut supérieur de l'électronique et du numérique (ISEN)

Subjects
Physics, Convection, Multidisciplinary, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, K-type main-sequence star, FOS: Physical sciences, Astronomy, Astrophysics::Cosmology and Extragalactic Astrophysics, Radius, Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 01 natural sciences, Asteroseismology, Stars, Astrophysics - Solar and Stellar Astrophysics, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Solar-like oscillations, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Main sequence, Envelope (waves)
Abstract

Delta Scuti (delta Sct) stars are opacity-driven pulsators with masses of 1.5-2.5M$_{\odot}$, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30 per cent of the star and excites a rich spectrum of resonant acoustic modes. Based on the solar example, with no firm theoretical basis, models predict that the convective envelope in delta Sct stars extends only about 1 per cent of the radius, but with sufficient energy to excite solar-like oscillations. This was not observed before the Kepler mission, so the presence of a convective envelope in the models has been questioned. Here we report the detection of solar-like oscillations in the delta Sct star HD 187547, implying that surface convection operates efficiently in stars about twice as massive as the Sun, as the ad hoc models predicted., to appear as a Letter to Nature

Published
2011

16. The first evidence for multiple pulsation axes: a new rapidly oscillating Ap star in the Kepler field, KIC 10195926

Author

H. Kjeldsen, L. A. Balona, V. G. Elkin, K. Uytterhoeven, A. P. Hatzes, Søren Frimann, L. Bigot, S. D. Kawaler, J. Christensen-Dalsgaard, Hiromoto Shibahashi, M. Gruberbauer, D. W. Kurtz, M. S. Cunha, S. Frandsen, I. M. Brandão, T. Lueftinger, and Hideyuki Saio

Subjects
Physics, Rotation period, Field (physics), 010308 nuclear & particles physics, Mode (statistics), Astronomy and Astrophysics, Astrophysics, Star (graph theory), Rotation, 01 natural sciences, Stars, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Variation (astronomy), 010303 astronomy & astrophysics, Rapidly oscillating Ap star, Astrophysics::Galaxy Astrophysics
Abstract

We have discovered a new rapidly oscillating Ap star among the Kepler Mission target stars, KIC 10195926. This star shows two pulsation modes with periods that are amongst the longest known for roAp stars at 17.1 min and 18.1 min, indicating that the star is near the terminal age main sequence. The principal pulsation mode is an oblique dipole mode that shows a rotationally split frequency septuplet that provides information on the geometry of the mode. The secondary mode also appears to be a dipole mode with a rotationally split triplet, but we are able to show within the improved oblique pulsator model that these two modes cannot have the same axis of pulsation. This is the first time for any pulsating star that evidence has been found for separate pulsation axes for different modes. The two modes are separated in frequency by 55 microHz, which we model as the large separation. The star is an alpha^2 CVn spotted magnetic variable that shows a complex rotational light variation with a period of Prot = 5.68459 d. For the first time for any spotted magnetic star of the upper main sequence, we find clear evidence of light variation with a period of twice the rotation period; i.e. a subharmonic frequency of $\nu_{\rm rot}/2$. We propose that this and other subharmonics are the first observed manifestation of torsional modes in an roAp star. From high resolution spectra we determine Teff = 7400 K, log g = 3.6 and v sin i = 21 km/s. We have found a magnetic pulsation model with fundamental parameters close to these values that reproduces the rotational variations of the two obliquely pulsating modes with different pulsation axes. The star shows overabundances of the rare earth elements, but these are not as extreme as most other roAp stars. The spectrum is variable with rotation, indicating surface abundance patches.

Published
2011

17. Kepler photometry of KIC 10661783: a binary star with total eclipses and δ Scuti pulsations

Author

J. Christensen-Dalsgaard, Peter Tenenbaum, John Southworth, H. Kjeldsen, Krešimir Pavlovski, W. Zima, Andrej Prsa, J. D. Twicken, D. W. Kurtz, R. L. Gilliland, Miles T. Cote, S. L. Kim, Barry Smalley, Conny Aerts, S. D. Kawaler, H. Bruntt, and Holger Lehmann

Subjects
Physics, Frequency analysis, 010308 nuclear & particles physics, Phase (waves), Astronomy and Astrophysics, Astrophysics, Light curve, 01 natural sciences, law.invention, Photometry (optics), Stars, Amplitude, Space and Planetary Science, law, 0103 physical sciences, Binary star, Astrophysics::Solar and Stellar Astrophysics, Roche lobe, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics
Abstract

We present Kepler satellite photometry of KIC 10661783, a short-period binary star system which shows total eclipses and multi-periodic delta Scuti pulsations. A frequency analysis of the eclipse-subtracted light curve reveals at least 68 frequencies of which 55 or more can be attributed to pulsation modes. The main limitation on this analysis is the frequency resolution within the 27-day short-cadence light curve. Most of the variability signal lies in the frequency range 18 to 31 c/d, with amplitudes between 0.1 and 4 mmag. One harmonic term (2.f) and a few combination frequencies (f_i+f_j) have been detected. From a plot of the residuals versus orbital phase we assign the pulsations to the primary star in the system. The pulsations were removed from the short-cadence data and the light curve was modelled using the Wilson-Devinney code. We are unable to get a perfect fit due to the residual effects of pulsations and also to the treatment of reflection and reprocessing in the light curve model. A model where the secondary star fills its Roche lobe is favoured, which means that KIC 10661783 can be classified as an oEA system. Further photometric and spectroscopic observations will allow the masses and radii of the two stars to be measured to high precision and hundreds of delta Scuti pulsation frequencies to be resolved. This could lead to unique constraints on theoretical models of delta Scuti stars, if the evolutionary history of KIC 10661783 can be accounted for.

Published
2011

18. Regularities in frequency spacings of δ Scuti stars: the Kepler star KIC 9700322★

Author

A. A. Pamyatnykh, K. Uytterhoeven, J. K. Hollek, Patrick Lenz, J. Christensen-Dalsgaard, Marcella Marconi, Barry Smalley, Róbert Szabó, D. W. Kurtz, Khadeejah A. Ibrahim, L. A. Balona, Giovanni Catanzaro, Kamal Uddin, Juan Carlos Suárez, H. Kjeldsen, Michael N. Fanelli, V. Ripepi, and Michel Breger

Subjects
Delta, Physics, Stars, Amplitude, Space and Planetary Science, Frequency separation, Modulation (music), Astronomy and Astrophysics, Astrophysics, Star (graph theory), Low frequency, Rotation
Abstract

In the faint star KIC 9700322 observed by the Kepler satellite, 76 frequencies with amplitudes from 14 to 29000 ppm were detected. The two dominant frequencies at 9.79 and 12.57 c/d (113.3 and 145.5 \mu Hz), interpreted to be radial modes, are accompanied by a large number of combination frequencies. A small additional modulation with a 0.16 c/d frequency is also seen; this is interpreted to be the rotation frequency of the star. The corresponding prediction of slow rotation is confirmed by a spectrum from which v sin i = 19 \pm 1 km/s is obtained. The analysis of the spectrum shows that the star is one of the coolest {\delta} Sct variables. We also determine Teff = 6700 \pm 100 K and log g = 3.7 \pm 0.1, compatible with the observed frequencies of the radial modes. Normal solar abundances are found. An \ell = 2 frequency quintuplet is also detected with a frequency separation consistent with predictions from the measured rotation rate. A remarkable result is the absence of additional independent frequencies down to an amplitude limit near 14 ppm, suggesting that the star is stable against most forms of nonradial pulsation. The frequency spectrum of this star emphasizes the need for caution in interpreting low frequencies in {\delta} Sct stars as independent gravity modes. A low frequency peak at 2.7763 c/d in KIC 9700322 is, in fact, the frequency difference between the two dominant modes and is repeated over and over in various frequency combinations involving the two dominant modes. The relative phases of the combination frequencies show a strong correlation with frequency, but the physical significance of this result is not clear.

Published
2011

19. 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

20. Atmospheric parameters and pulsational properties for a sample of δ Sct, γ Dor and hybrid Kepler targets★

Author

L. A. Balona, Marcella Marconi, V. Ripepi, H. Kjeldsen, J. Christensen-Dalsgaard, Giovanni Catanzaro, Róbert Szabó, William J. Borucki, Barry Smalley, Mário J. P. F. G. Monteiro, D. W. Kurtz, S. Bernabei, J. C. Suárez, David G. Koch, K. Uytterhoeven, H. Bruntt, and A. Grigahcène

Subjects
Physics, 010308 nuclear & particles physics, Star (game theory), Boundary (topology), Astronomy and Astrophysics, Astrophysics, Type (model theory), Effective temperature, Surface gravity, 01 natural sciences, Spectral line, Stars, Amplitude, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We report spectroscopic observations for 19 $\delta$\,Sct candidates observed by the {\it Kepler} satellite both in long and short cadence mode. For all these stars, by using spectral synthesis, we derive the effective temperature, the surface gravity and the projected rotational velocity. An equivalent spectral type classification has been also performed for all stars in the sample. These determinations are fundamental for modelling the frequency spectra that will be extracted from the {\it Kepler} data for asteroseismic inference. For all the 19 stars, we present also periodograms obtained from {\it Kepler} data. We find that all stars show peaks in both low- ($\gamma$\,Dor; g mode) and high-frequency ($\delta$\,Sct; p mode) regions. Using the amplitudes and considering 5\,c/d as a boundary frequency, we classified 3 stars as pure $\gamma$\,Dor, 4 as $\gamma$\,Dor\,-\,$\delta$\ hybrid, Sct, 5 as $\delta$\,Sct\,-\,$\gamma$\,Dor hybrid, and 6 as pure $\delta$\,Sct. The only exception is the star KIC\,05296877 which we suggest could be a binary.

Published
2010

21. Kepler observations of rapidly oscillating Ap, δ Scuti and γ Doradus pulsations in Ap stars

Author

L. A. Balona, M. S. Cunha, D. W. Kurtz, I. M. Brandão, M. Gruberbauer, H. Saio, R. Østensen, V. G. Elkin, W. J. Borucki, J. Christensen-Dalsgaard, H. Kjeldsen, D. G. Koch, and S. T. Bryson

Subjects
Delta, Physics, Stars, 010308 nuclear & particles physics, Space and Planetary Science, 0103 physical sciences, Astronomy and Astrophysics, Time resolution, Astrophysics, Star (graph theory), 010303 astronomy & astrophysics, 01 natural sciences, Kepler
Abstract

Observations of the A5p star KIC 8677585 obtained during the Kepler 10-d commissioning run with 1-min time resolution show that it is a roAp star with several frequencies with periods near 10 min. In addition, a low frequency at 3.142 cycles/day is also clearly present. Multiperiodic gamma Doradus and delta Scuti pulsations, never before seen in any Ap star, are present in Kepler observations of at least three other Ap stars. Since gamma Doradus pulsations are seen in Ap stars, it is likely that the low-frequency in KIC 8677585 is also a gamma Doradus pulsation. The simultaneous presence of both gamma Doradus and roAp pulsations and the unexpected detection of delta Scuti and gamma Doradus pulsations in Ap stars present new opportunities and challenges for the interpretation of these stars.

Published
2010

23. A spectroscopic search for non-radial pulsations in the Scuti star Bootis

Author

J. Christensen-Dalsgaard, Lucio Paternò, M. P. Di Mauro, Rita Ventura, and Giovanni Catanzaro

Subjects
Physics, Series (mathematics), Flux, Astronomy and Astrophysics, Astrophysics, Star (graph theory), Bin, Azimuth, Wavelength, symbols.namesake, Fourier transform, Space and Planetary Science, symbols, Line (formation)
Abstract

High-resolution spectroscopic observations of the rapidly rotating delta Scuti star gamma Bootis have been carried out on 2005, over 6 consecutive nights, in order to search for line-profile variability. Time series, consisting of flux measurements at each wavelength bin across the TiII 4571.917 A line profile as a function of time, have been Fourier analyzed. The results confirm the early detection reported by Kennelly et al. (1992) of a dominant periodic component at frequency 21.28 c/d in the observer's frame, probably due to a high azimuthal order sectorial mode. Moreover, we found other periodicities at 5.06 c/d, 12.09 c/d, probably present but not secure, and at 11.70 c/d and 18.09 c/d, uncertain. The latter frequency, if present, should be identifiable as another high azimuthal order sectorial mode and three additional terms, probably due to low-l modes, as proved by the analysis of the first three moments of the line. Owing to the short time baseline and the one-site temporal sampling we consider our results only preliminary but encouraging for a more extensive multisite campaign. A refinement of the atmospheric physical parameters of the star has been obtained from our spectroscopic data and adopted for preliminary computations of evolutionary models of gamma Bootis.

Published
2007

24. Microscopic Diffusion in Stellar Evolution Codes: First Comparisons Results of ESTA-Task 3

Author

Mário J. P. F. G. Monteiro, J. Christensen-Dalsgaard, Pierre Morel, Axel Weiss, Yveline Lebreton, Marcella Marconi, Scilla Degl'Innocenti, S. Théado, P. G. Prada Moroni, Josefina Montalbán, A. Hui-Bon-Hoa, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique et de Géophysique [Liège], Université de Liège, 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), Laboratoire Astrophysique de Toulouse-Tarbes (LATT), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), 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), Université Fédérale Toulouse Midi-Pyrénées, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), 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), 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), 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), 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), 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 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), Université Nice Sophia Antipolis (1965 - 2019) (UNS), 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 Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Work (thermodynamics), 010308 nuclear & particles physics, Astrophysics (astro-ph), General Engineering, Comparison results, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Task (project management), [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Space and Planetary Science, 0103 physical sciences, Statistical physics, Diffusion (business), Concentration gradient, 010303 astronomy & astrophysics, Stellar evolution
Abstract

We present recent work undertaken by the Evolution and Seismic Tools Activity (ESTA) team of the CoRoT Seismology Working Group. The new ESTA-Task 3 aims at testing, comparing and optimising stellar evolution codes which include microscopic diffusion of the chemical elements resulting from pressure, temperature and concentration gradients. The results already obtained are globally satisfactory, but some differences between the different numerical tools appear that require further investigations., to appear in "Stellar Evolution and Seismic Tools for Asteroseismology", (Eds) C. W. Straka, Y. Lebreton and M. J. P. F. G. Monteiro, EAS Publications Series, 2007

Published
2007

25. A bright outlook for helio- and asteroseismology

Author

J. Christensen-Dalsgaard, Tong, Vincent C.H., and Garcia, Rafael A.

Subjects
Physics, Extraterrestrial life, Internal rotation, Planetary science and astrobiology, Solid Earth Geophysics, Astronomy, Asteroseismology
Abstract

As documented in the following, very substantial results have already been obtained from helio- and asteroseismology, based on huge observational projects, such as the GONG project, the helioseismic instruments on the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) satellites, and asteroseismology with the CoRoT and Kepler missions. But this is just the beginning. New asteroseismic projects are on the way, and there are also plans for new developments in observational helioseismology, including multi-wavelength observations (Hill et al., 2013). For local helioseismology a potential breakthrough will come from ESA's Solar Orbiter mission (Gandorfer et al., 2011), which will for the first time allow detailed investigations of the regions near the solar poles.However, there is much to be done with the existing data, and much to be done further to develop the analysis techniques. The helioseismic data have been far from fully exploited, with the inverse analyses being typically based just on a small fraction of the available observations. In particular, the high-resolution observations from the Helioseismic and Magnetic Imager (HMI) instrument on SDO may provide reliable frequency data on high- degree modes, which would allow more detailed investigations of the thermodynamics of the region of helium ionization (e.g., Rabello-Soares et al., 2000). Also, the base of the solar convective envelope certainly deserves further investigation, including an updated search for possible latitude variations (Monteiro and Thompson, 1998) and a follow-up to the hint of solar-cycle variations found by Baldner and Basu (2008). The helioseismic data on frequency splittings have been extensively used to study variations of solar internal rotation during the solar cycle (for a recent example, see Howe et al., 2013). However, further work is certainly required on constraining the rotation of the solar core, where improvements in the inversion techniques may allow a better localization and balance between resolution and error. As documented in the following, very substantial results have already been obtained from helio- and asteroseismology, based on huge observational projects, such as the GONG project, the helioseismic instruments on the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) satellites, and asteroseismology with the CoRoT and Kepler missions. But this is just the beginning. New asteroseismic projects are on the way, and there are also plans for new developments in observational helioseismology, including multi-wavelength observations (Hill et al., 2013). For local helioseismology a potential breakthrough will come from ESA's Solar Orbiter mission (Gandorfer et al., 2011), which will for the first time allow detailed investigations of the regions near the solar poles.However, there is much to be done with the existing data, and much to be done further to develop the analysis techniques. The helioseismic data have been far from fully exploited, with the inverse analyses being typically based just on a small fraction of the available observations. In particular, the high-resolution observations from the Helioseismic and Magnetic Imager (HMI) instrument on SDO may provide reliable frequency data on high- degree modes, which would allow more detailed investigations of the thermodynamics of the region of helium ionization (e.g., Rabello-Soares et al., 2000). Also, the base of the solar convective envelope certainly deserves further investigation, including an updated search for possible latitude variations (Monteiro and Thompson, 1998) and a follow-up to the hint of solar-cycle variations found by Baldner and Basu (2008). The helioseismic data on frequency splittings have been extensively used to study variations of solar internal rotation during the solar cycle (for a recent example, see Howe et al., 2013). However, further work is certainly required on constraining the rotation of the solar core, where improvements in the inversion techniques may allow a better localization and balance between resolution and error.

Published
2015

26. Commission 12: Solar Radiation & Structure

Author

Thomas. J. Bogdan, Valentin Martínez Pillet, M. Asplund, J. Christensen-Dalsgaard, G. Cauzzi, L. E. Cram, D. Dravins, W. Gan, P. Henzl, A. Kosovichev, J. T. Mariska, M. G. Rovira, and P. Venkatakrishnan

Subjects
Space and Planetary Science, Astronomy and Astrophysics
Abstract

Commission 12 covers research on the internal structure and dynamics of the Sun, the “quiet” solar atmosphere, solar radiation and its variability, and the nature of relatively stable magnetic structures like sunspots, faculae and the magnetic network. There is considerable productive overlap with the other Commissions of Division II as investigations move progressively toward the fertile intellectual boundaries between traditional research disciplines. In large part, the solar magnetic field provides the linkage that connects these diverse themes. The same magnetic field that produces the more subtle variations of solar structure and radiative output over the 11 yr activity cycle is also implicated in rapid and often violent phenomena such as flares, coronal mass ejections, prominence eruptions, and episodes of sporadic magnetic reconnection.The last three years have again brought significant progress in nearly all the research endeavors touched upon by the interests of Commission 12. The underlying causes for this success remain the same: sustained advances in computing capabilities coupled with diverse observations with increasing levels of spatial, temporal and spectral resolution. It is all but impossible to deal with these many advances here in anything except a cursory and selective fashion. Thankfully, theLiving Reviews in Solar Physicsacute; has published several extensive reviews over the last two years that deal explicitly with issues relevant to the purview of Commission 12. The reader who is eager for a deeper and more complete understanding of some of these advances is directed tohttp://www.livingreviews.orgfor access to these articles.

Published
2005

28. First Results from the Hertzsprung SONG Telescope: Asteroseismology of the G5 Subgiant StarμHerculis

Author

Timothy R. White, René Tronsgaard, Jens Jessen-Hansen, M. Fredslund Andersen, Pere L. Palle, S. Frandsen, Torben Arentoft, Rasmus Handberg, Frank Grundahl, J. Skottfelt, J. Christensen-Dalsgaard, Victoria Antoci, M. Sloth Lundkvist, A. Norup Sørensen, P. Kjærgaard Rasmussen, T. R. Bedding, H. Kjeldsen, I. Karovicova, Kasper Harpsøe, William J. Chaplin, V. Silva Aguirre, G. Houdek, Michael I. Andersen, E. Weiss, K. Brogaard, Christoffer Karoff, U. G. Jørgensen, Simon Albrecht, and M. N. Lund

Subjects
oscillations [stars], Rotation period, Stellar mass, Hertzsprung–Russell diagram, observational [methods], FOS: Physical sciences, asteroseismology, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Asteroseismology, law.invention, Telescope, symbols.namesake, law, 0103 physical sciences, data analysis [methods], individual: HD 161797 [stars], Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Subgiant, Oscillation, Astronomy and Astrophysics, Astrophysics - Solar and Stellar Astrophysics, Convection zone, Space and Planetary Science, symbols, Astrophysics::Earth and Planetary Astrophysics, spectrographs [instrumentation]
Abstract

We report the first asteroseismic results obtained with the Hertzsprung SONG Telescope from an extensive high-precision radial-velocity observing campaign of the subgiant muHerculis. The data set was collected during 215 nights in 2014 and 2015. We detected a total of 49 oscillation modes with l values from 0 to 3, including some l = 1 mixed modes. Based on the rotational splitting observed in l = 1 modes, we determine a rotational period of 52 days and a stellar inclination angle of 63 degrees. The parameters obtained through modeling of the observed oscillation frequencies agree very well with independent observations and imply a stellar mass between 1.11 and 1.15M_sun and an age of 7.8+/-0.4 Gyr. Furthermore, the high-quality data allowed us to determine the acoustic depths of the He II ionization layer and the base of the convection zone., Comment: 17 pages, 15 figures. Accepted for publication in ApJ

Published
2017

29. Stellar Pulsations : Impact of New Instrumentation and New Insights

Author

J.C. Suárez, R. Garrido, L. A. Balona, J. Christensen-Dalsgaard, J.C. Suárez, R. Garrido, L. A. Balona, and J. Christensen-Dalsgaard

Subjects
Pulsating stars--Congresses, Stellar oscillations--Congresses
Abstract

Analyses of photometric time series obtained from the MOST, CoRoT and Kepler space missions were presented at the 20th conference on Stellar Pulsations (Granada, September 2011). These results are leading to a re-appraisal of our views on stellar pulsation in some stars and posing some new and unexpected challenges. The very important and exciting role played by innovative ground-based observational techniques, such as interferometric measurements of giant pulsating stars and high-resolution spectroscopy in the near infrared, is also discussed. These Proceedings are distinguished by the format of the conference, which brings together a variety of related but different topics not found in other meetings of this nature.

Published
2012

30. Theoretical Aspects of Asteroseismology

Author

J. Christensen-Dalsgaard

Subjects
010504 meteorology & atmospheric sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences, 0105 earth and related environmental sciences
Abstract

Asteroseismology depends on the ability to determine frequencies for identified modes of stellar oscillation, and to use these frequencies to probe stellar interiors. Thus crucial aspects are the dependence of the frequencies on stellar properties, and the likelihood that modes are excited to observable amplitudes. I provide a brief overview of these issues and some remarks about how the frequencies may be analyzed, as a background for the more detailed presentations elsewhere in the proceedings.

Published
1998

31. Spherical and Aspherical Structure of the Sun: First Year of Soho/Mdi Observations

Author

A.G. Kosovichev, R. Nigam, P.H. Scherrer, J. Schou, J. Christensen-Dalsgaard, W.A. Dziembowski, P.H. Goode, D.O. Gough, J. Reiter, and E.J. Rhodes

Subjects
Astrophysics::Solar and Stellar Astrophysics
Abstract

We report the initial results of one year of continuous observations of the Sun‘s internal structure from the Michelson Doppler Imager (MDI) on board SOHO. The results have been obtained by inverting frequencies of p and f modes determined with two different methods of averaging over split multiplets. Small systematic differences between the two frequency sets depend primarily on mode frequencies, and, thus, did not significantly affect the inversions. A preliminary study of the systematic effects resulting from asymmetry of oscillation power peaks has also shown no significant influence on the inversion results. The inferred sound-speed profile is in general agreement with the previous data from MDI and ground-based networks. In the energy-generating core, the resolution is substantially improved, and the inversion results indicate a sharp negative perturbation of the sound speed in the core, tending to a positive value near the center. High-precision measurements of the f-mode frequencies have been used to determine the seismic radius of the Sun. The global asphericity estimated from frequency variation across the split mode multiplets has been found to be small, and is consistent with the asphericity during the previous activity minimum. Variations of the solar frequencies during the first year of MDI observations have also been detected.

Published
1998

32. The Influence of A Magnetic Field on Radiative Damping of Magnetoatmospheric Oscillations

Author

Dipankar Banerjee, S.S. Hasan, and J. Christensen-Dalsgaard

Abstract

We investigate the influence of a magnetic field on the radiative damping of magnetoatmospheric waves, extending our previous work on the adiabatic modes of an isothermal stratified atmosphere with a uniform vertical magnetic field. Banerjee, Hasan & Christensen-Dalsgaard (1996, 1997) generalized this work to include radiative effects using Newton's law of cooling for a weak magnetic field. The present study examines the variation of the mode damping rate with increasing magnetic field strength. We find that a moderate field suppresses radiative damping.

Published
1998

33. TURBULENCE IN ASTROPHYSICS: Stars

Author

V. M. Canuto and J. Christensen-Dalsgaard

Subjects
Physics, Turbulence, Astrophysics, Reynolds stress, Condensed Matter Physics, Cosmology, Physics::Fluid Dynamics, Interstellar medium, Stars, Supernova, Astrophysics::Solar and Stellar Astrophysics, Differential rotation, Astrophysics::Earth and Planetary Astrophysics, Helioseismology, Astrophysics::Galaxy Astrophysics
Abstract

▪ Abstract Turbulence is ubiquitous in astrophysics, ranging from cosmology, interstellar medium to stars, supernovae, accretion disks, etc. Large scales and small viscosities combine to form large Reynolds numbers. Because it is not possible in a single article to review all the above scenarios, we limit ourselves to stars, in which thermal instabilities give rise to turbulent convection as the dominant heat transport mechanism. (Accretion disks, where shear instabilities dominate the outward transport of angular momentum, will be the subject of a second article, planned for Volume 31.) Because of the lack of a satisfactory theory, turbulence constitutes a bottleneck that prevents astrophysical models from being fully predictive. Because continued use of phenomenological turbulence expressions would make astrophysical models perennially unpredictive, a way must be found to make astrophysical models as prognostic as possible. In addition to the difficulties brought about by turbulence, astrophysical settings introduce “malicious conditions,” of which the most refractory to a satisfactory quantification are compressibility (caused by the large density excursions that characterize convective zones in stars) and rotation. Basic understanding of how they affect turbulence in general is still rather sketchy. Reasons for the choice of stars and accretion disks as prototype examples are the following: The underlying instabilities are very basic; laboratory and direct numerical simulations data help constrain theoretical models; and new observational data, especially from helioseismology, help discriminate among different models with unprecedented accuracy.

Published
1998

34. Internal structure and rotation of the Sun: First results from the MDI data

Author

J. Aloise, Sarbani Basu, J. L. R. Saba, P. M. Giles, K. Leibrand, D. Mathur, A. Burnette, Alan M. Title, J. Christensen-Dalsgaard, C. De Forest, Alexander G. Kosovichev, Theodore D. Tarbell, R. S. Bogart, Juri Toomre, Keith Scott, P. N. Milford, L. Bacon, Takashi Sekii, Jesper Schou, M. Rubin, I. Zayer, J. T. Hoeksema, M. Morrison, D. O. Gough, T. L. Duvall, Michael Thompson, Roger T. Howe, R. I. Bush, Philip H. Scherrer, C. J. Wolfson, Edward J. Rhodes, R. Nigam, S. D. Williams, and Werner Däppen

Subjects
Physics, Oscillation, Computer Science::Information Retrieval, Rotation, Convective Boundary Layer, Spectral line, Computational physics, symbols.namesake, Amplitude, Convection zone, symbols, Astrophysics::Solar and Stellar Astrophysics, Doppler effect, Noise (radio)
Abstract

The Medium-l Program of the Michelson Doppler Imager (MDI) instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∼ 300. The initial results show that the noise in the Medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. In a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer.

Published
1997

35. 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
Full Text
View/download PDF

36. 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

37. Internal Structure

Author

J. Christensen-Dalsgaard

Abstract

In this section I concentrate on the spherically symmetric aspects of solar structure, corresponding to “classical” stellar evolution models. Such models are characterized by a number of simplifying assumptions, as well as by the physical properties of matter in the star, conveniently labeled “micro-physics”. The latter include descriptions of the equation of state, the opacity and the nuclear reaction rates; in addition, molecular diffusion, included in several recent calculations, should be considered as part of the micro-physics. The assumptions in the standard calculations, simplifying what might be called the macro-physics, include the neglect of effects of rotation and magnetic fields (implicit in the assumption of spherical symmetry), as well as the assumption that material mixing occurs only in convectively unstable regions, or possibly as a result of molecular diffusion and settling; also, convective energy transport is treated crudely through some form of mixing-length approximation and the contribution to hydrostatic balance from the turbulent motion in the convection zone, usually called turbulent pressure, is ignored.

Published
1995

38. Estimating the p-mode frequencies of the solar twin 18 Scorpii

Author

Pascal Petit, Mário J. P. F. G. Monteiro, T. L. Campante, M. Bazot, Sylvie Vauclair, Valérie Van Grootel, Hervé Carfantan, J. Christensen-Dalsgaard, William J. Chaplin, Sérgio F. Sousa, Torben Arentoft, H. Kjeldsen, M. Castro, B. Dintrans, Xavier Dumusque, José-Dias do Nascimento, A.-M. Broomhall, S. Théado, T. R. Bedding, and N. C. Santos

Subjects
Physics, 010504 meteorology & atmospheric sciences, Series (mathematics), Spectrometer, Basis (linear algebra), Oscillation, Mode (statistics), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Asteroseismology, Seismic analysis, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Focus (optics), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract

Solar twins have been a focus of attention for more than a decade, because their structure is extremely close to that of the Sun. Today, thanks to high-precision spectrometers, it is possible to use asteroseismology to probe their interiors. Our goal is to use time series obtained from the HARPS spectrometer to extract the oscillation frequencies of 18 Sco, the brightest solar twin. We used the tools of spectral analysis to estimate these quantities. We estimate 52 frequencies using an MCMC algorithm. After examination of their probability densities and comparison with results from direct MAP optimization, we obtain a minimal set of 21 reliable modes. The identification of each pulsation mode is straightforwardly accomplished by comparing to the well-established solar pulsation modes. We also derived some basic seismic indicators using these values. These results offer a good basis to start a detailed seismic analysis of 18 Sco using stellar models., Comment: 12 pages, 6 figures, to be published in A&A

Published
2012
Full Text
View/download PDF

39. 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

40. 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

41. Asteroseismic modelling of the solar-type subgiant star β Hydri

Author

G. Doğan, Torben Arentoft, T. S. Metcalfe, I. M. Brandão, M. S. Cunha, H. Kjeldsen, J. Christensen-Dalsgaard, T. R. Bedding, H. Bruntt, Centro de Astrofisica da Universidade do Porto (CAUP), Department of Physics and Astronomy, Aarhus University, Sydney Institute for Astronomy (SIfA), High Altitude Observatory, National Center for Atmospheric Research, 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), Haute résolution angulaire en astrophysique, 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, and 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)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Subgiant, Oscillation, Metallicity, Spectral density, Astronomy and Astrophysics, Astrophysics, Type (model theory), 01 natural sciences, Weighting, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Stellar structure, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; Context. Comparing models and data of pulsating stars is a powerful way to understand the stellar structure better. Moreover, such comparisons are necessary to make improvements to the physics of the stellar models, since they do not yet perfectly represent either the interior or especially the surface layers of stars. Because beta Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims: The goal of the present work is to search for a representative model of the solar-type star beta Hydri, based on up-to-date non-seismic and seismic data. Methods: We present a revised list of frequencies for 33 modes, which we produced by analysing the power spectrum of the published observations again using a new weighting scheme that minimises the daily sidelobes. We ran several grids of evolutionary models with different input parameters and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of beta Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed frequencies of beta Hydri: (i) we assume that the best model is the one that reproduces the star's interior based on the radial oscillation frequencies alone, to which we have applied the correction for the near-surface effects; (ii) we assume that the best model is the one that produces the lowest value of the chi-square (chi2), i.e. that minimises the difference between the observed frequencies of all available modes and the model predictions, after all model frequencies are corrected for near-surface effects. Results: We show that after applying a correction for near-surface effects to the frequencies of the best models, we can reproduce the observed modes well, including those that have mixed mode character. The model that gives the lowest value of the chi2 is a post-main-sequence model with a mass of 1.04 M&sun; and a metallicity slightly lower than that of the Sun. Our results underscore the importance of having individual frequencies to constrain the properties of the stellar model.

Published
2011

42. 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

43. 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

44. Pulsation Theory and Stellar Structure

Author

J. Christensen-Dalsgaard

Subjects
Physics, Stellar mass, Opacity, Stellar mass loss, Young stellar object, Stellar collision, Other Fields of Physics, Astrophysics::Solar and Stellar Astrophysics, Astronomy, Stellar structure, Astrophysics::Earth and Planetary Astrophysics, Stellar evolution, Astrophysics::Galaxy Astrophysics
Abstract

Observed periods of pulsating stars provide information about the properties of the stars. As examples I here consider double-mode pulsators, solar-like oscillations and δ Scuti stars. The ongoing expansion in the observational efforts in this area may be expected to lead to increasingly detailed tests of stellar evolution theory.

Published
1993

45. Hybrid γ Doradus–δ Scuti Pulsators: New Insights into the Physics of the Oscillations from Kepler Observations

Author

Andreas M. Kaiser, J. M. Jenkins, J. Nuspl, L. A. Balona, J. Molenda-Zakowicz, Jadwiga Daszyńska-Daszkiewicz, Gerald Handler, Mário J. P. F. G. Monteiro, Marcella Marconi, G. Houdek, K. Uytterhoeven, Rita Ventura, M. Di Criscienzo, David G. Koch, J. A. Guzik, J. M. Nemec, A. García Hernández, H. Kjeldsen, S. Marin-Ruiz, Marc-Antoine Dupret, J. Christensen-Dalsgaard, Paul A. Bradley, Juan Carlos Suárez, Michel Breger, William J. Borucki, M. D. Suran, D. W. Kurtz, V. Ripepi, A. Moya, S. Bernabei, Giovanni Catanzaro, M. Paparo, Jason Jackiewicz, R. L. Gilliland, Victoria Antoci, Rafael A. García, A. Grigahcène, Róbert Szabó, Markus Roth, P. Mathias, Timothy M. Brown, and Holger Lehmann

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Order (ring theory), Astronomy and Astrophysics, Astrophysics, Spectral line, Base (group theory), Stars, Amplitude, Convection zone, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Variable star, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Envelope (waves)
Abstract

Observations of the pulsations of stars can be used to infer their interior structure and test theoretical models. The main sequence $\gamma$ Doradus (Dor) and $\delta$ Scuti (Sct) stars with masses 1.2-2.5 $M_{\sun}$ are particularly useful for these studies. The $\gamma$ Dor stars pulsate in high-order $g$ modes with periods of order 1 day, driven by convective blocking at the base of their envelope convection zone. The $\delta$ Sct stars pulsate in low-order $g$ and $p$ modes with periods of order 2 hours, driven by the $\kappa$ mechanism operating in the Heii ionization zone. Theory predicts an overlap region in the Hertzsprung-Russell diagram between instability regions, where 'hybrid' stars pulsating in both types of modes should exist. The two types of modes with properties governed by different portions of the stellar interior provide complementary model constraints. Among the known $\gamma$ Dor and $\delta$ Sct stars, only four have been confirmed as hybrids. Now, analysis of combined Quarter 0 and Quarter 1 Kepler data for hundreds of variable stars shows that the frequency spectra are so rich that there are practically no pure $\delta$ Sct or $\gamma$ Dor pulsators, i.e. essentially all of the stars show frequencies in both the $\delta$ Sct and $\gamma$ Dor frequency range. A new observational classification scheme is proposed that takes into account the amplitude as well as the frequency, and is applied to categorize 234 stars as $\delta$ Sct, $\gamma$ Dor, $\delta$ Sct/$\gamma$ Dor or $\gamma$ Dor/$\delta$ Sct hybrids., Comment: 6 pages with 4 figures and 1 table - submitted to ApJL

Published
2010

46. 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

47. 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

48. 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

49. Sources of uncertainty in direct seismological measurements of the solar helium abundance

Author

Douglas Gough, J. Christensen-Dalsgaard, Alexander G. Kosovichev, W. Daeppen, Michael Thompson, and W. A. Dziembowski

Subjects
Physics, Equation of state, Standard solar model, Convection zone, Space and Planetary Science, Ionization, Astronomy and Astrophysics, Astrophysics, Helioseismology, Residual, Solar physics, Adiabatic process, Computational physics
Abstract

The methods by which Dappen et al. (1988, 1990, 1991) and Dziembowski et al. (1990, 1991, 1992) recently obtained discrepant estimates of the helium abundance in the solar convection zone are compared. The aim of the investigation reported in this paper is to identify the main source of the discrepancy. Using as proxy data eigenfrequencies of a set of modes of a theoretical solar model, computed with the same physics as were the frequencies of a reference model with which these data are compared, the two methods yield similar results. Thus we ascertain that the principal source of the discrepancy is not in the inversions themselves, which yield essentially a measure of the variation of the adiabatic exponent gamma of the material in the He II ionization zone. Instead it is in the approximations adopted in the treatment of heavy elements in the equation of state used to relate the variation of gamma to chemical composition. We obtain acceptably consistent results when inverting solar data by two methods using the same equation of state. We attempt to identify the likely residual sources of uncertainty.

Published
1992

50. The Future

Author

C. Aerts, J. Christensen-Dalsgaard, and D. W. Kurtz

Published
2009

Catalog

Books, media, physical & digital resources
See catalog results