43 results on '"Benomar, O"'
Search Results
2. Asteroseismic detection of latitudinal differential rotation in 13 Sun-like stars
- Author
-
Benomar, O., Bazot, M., Nielsen, M. B., Gizon, L., Sekii, T., Takata, M., Hotta, H., Hanasoge, S., Sreenivasan, K. R., and Christensen-Dalsgaard, J.
- Published
- 2018
3. Asteroseismology of Solar-Type Stars with K2 : Detection of Oscillations in C1 Data
- Author
-
Chaplin, W. J., Lund, M. N., Handberg, R., Basu, S., Buchhave, L. A., Campante, T. L., Davies, G. R., Huber, D., Latham, D. W., Latham, C. A., Serenelli, A., Antia, H. M., Appourchaux, T., Ball, W. H., Benomar, O., Casagrande, L., Christensen-Dalsgaard, J., Coelho, H. R., Creevey, O. L., Elsworth, Y., García, R. A., Gaulme, P., Hekker, S., Kallinger, T., Karoff, C., Kawaler, S. D., Kjeldsen, H., Lundkvist, M. S., Marcadon, F., Mathur, S., Miglio, A., Mosser, B., Régulo, C., Roxburgh, I. W., Silva Aguirre, V., Stello, D., Verma, K., White, T. R., Bedding, T. R., Barclay, T., Buzasi, D. L., Dehuevels, S., Gizon, L., Houdek, G., Howell, S. B., Salabert, D., and Soderblom, D. R.
- Published
- 2015
- Full Text
- View/download PDF
4. A Distant Mirror: Solar Oscillations Observed on Neptune by the Kepler K2 Mission
- Author
-
Gaulme, P, Rowe, J. F, Bedding, T. R, Benomar, O, Corsaro, E, Davies, G. R, Hale, S. J, Howe, R, Garcia, R. A, Huber, D, Jimenez, A, Mathur, S, Mosser, B, Appourchaux, T, Boumier, P, Jackiewicz, J, Leibacher, J, Schmider, F.-X, Hammel, H. B, Lissauer, J. J, Marley, M. S, Simon, A. A, Chaplin, W. J, Elsworth,Y, Guzik, J. A, Murphy, N, and Aguirre, V. Silva
- Subjects
Astrophysics ,Lunar And Planetary Science And Exploration - Abstract
Starting in 2014 December, Kepler (K2) observed Neptune continuously for 49 days at a 1-minute cadence. The goals consisted of studying its atmospheric dynamics, detecting its global acoustic oscillations, and those of the Sun, which we report on here. We present the first indirect detection of solar oscillations in intensity measurements. Beyond the remarkable technical performance, it indicates how Kepler would see a star like the Sun. The result from the global asteroseismic approach, which consists of measuring the oscillation frequency at maximum amplitude max velocity and the mean frequency separation between mode overtones delta velocity, is surprising as the max velocity measured from Neptune photometry is larger than the accepted value. Compared to the usual reference max velocity of the sun equal to 3100 microhertz, the asteroseismic scaling relations therefore make the solar mass and radius appear larger by 13.8 plus or minus 5.8 percent and 4.3 plus or minus 1.9 percent, respectively. The higher max velocity is caused by a combination of the value of max velocity of the sun, being larger at the time of observations than the usual reference from SOHO/VIRGO/SPM (Variability of solar IRradiance and Gravity Oscillations / on board SOHO (Solar and Heliospheric Observatory) / Sun PhotoMeters) data (3160 plus or minus 10 microhertz), and the noise level of the K2 time series, being 10 times larger than VIRGO's. The peak-bagging method provides more consistent results: despite a low signal-to-noise ratio (S/N), we model 10 overtones for degrees iota equal 0, 1, 2. We compare the K2 data with simultaneous SOHO/VIRGO/SPM photometry and Bison (Birmingham Solar-Oscillations Network) velocity measurements. The individual frequencies, widths, and amplitudes mostly match those from VIRGO and BiSON within 1 sigma, except for the few peaks with the lowest S/N.
- Published
- 2016
- Full Text
- View/download PDF
5. Non-adiabatic study of the Kepler subgiant KIC 6442183
- Author
-
Grosjean M., Dupret M.A., Belkacem K., Benomar O., Deheuvels S., Samadi R., and Grigahcene A.
- Subjects
Physics ,QC1-999 - Abstract
Thanks to the precision of Kepler observations, [3] were able to measure the linewidth and amplitude of individual modes (including mixed modes) in several subgiant power spectra. We perform a forward modelling of a Kepler subgiant based on surface properties and observed frequencies. Non-adiabatic computations including a time- dependent treatment of convection give the lifetimes of radial and non-radial modes. Next, combining the lifetimes and inertias with a stochastic excitation model gives the amplitudes of the modes. We can now directly compare theoretical and observed linewidths and amplitudes of mixed-modes to obtain new constraints on our theoretical models.
- Published
- 2015
- Full Text
- View/download PDF
6. A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS
- Author
-
Huber, D. Chaplin, W.J. Chontos, A. Kjeldsen, H. Christensen-Dalsgaard, J. Bedding, T.R. Ball, W. Brahm, R. Espinoza, N. Henning, T. Jordán, A. Sarkis, P. Knudstrup, E. Albrecht, S. Grundahl, F. Andersen, M.F. Pallé, P.L. Crossfield, I. Fulton, B. Howard, A.W. Isaacson, H.T. Weiss, L.M. Handberg, R. Lund, M.N. Serenelli, A.M. Rørsted Mosumgaard, J. Stokholm, A. Bieryla, A. Buchhave, L.A. Latham, D.W. Quinn, S.N. Gaidos, E. Hirano, T. Ricker, G.R. Vanderspek, R.K. Seager, S. Jenkins, J.M. Winn, J.N. Antia, H.M. Appourchaux, T. Basu, S. Bell, K.J. Benomar, O. Bonanno, A. Buzasi, D.L. Campante, T.L. Çelik Orhan, Z. Corsaro, E. Cunha, M.S. Davies, G.R. Deheuvels, S. Grunblatt, S.K. Hasanzadeh, A. Di Mauro, M.P. A. García, R. Gaulme, P. Girardi, L. Guzik, J.A. Hon, M. Jiang, C. Kallinger, T. Kawaler, S.D. Kuszlewicz, J.S. Lebreton, Y. Li, T. Lucas, M. Lundkvist, M.S. Mann, A.W. Mathis, S. Mathur, S. Mazumdar, A. Metcalfe, T.S. Miglio, A. F. G. Monteiro, M.J.P. Mosser, B. Noll, A. Nsamba, B. Joel Ong, J.M. Örtel, S. Pereira, F. Ranadive, P. Régulo, C. Rodrigues, T.S. Roxburgh, I.W. Aguirre, V.S. Smalley, B. Schofield, M. Sousa, S.G. Stassun, K.G. Stello, D. Tayar, J. White, T.R. Verma, K. Vrard, M. Yildiz, M. Baker, D. Bazot, M. Beichmann, C. Bergmann, C. Bugnet, L. Cale, B. Carlino, R. Cartwright, S.M. Christiansen, J.L. Ciardi, D.R. Creevey, O. Dittmann, J.A. Nascimento, J.-D.D. Eylen, V.V. Fürész, G. Gagné, J. Gao, P. Gazeas, K. Giddens, F. Hall, O.J. Hekker, S. Ireland, M.J. Latouf, N. Lebrun, D. Levine, A.M. Matzko, W. Natinsky, E. Page, E. Plavchan, P. Mansouri-Samani, M. McCauliff, S. Mullally, S.E. Orenstein, B. Soto, A.G. Paegert, M. Van Saders, J.L. Schnaible, C. Soderblom, D.R. Szabó, R. Tanner, A. Tinney, C.G. Teske, J. Thomas, A. Trampedach, R. Wright, D. Yuan, T.T. Zohrabi, F.
- Abstract
We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R∗ = 2.943 ± 0.064 Ro), mass (M∗ = 1.212 ± 0.074 Mo), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 0.431 ± 0.062 g cm-3). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology. © 2019. The American Astronomical Society. All rights reserved..
- Published
- 2019
7. Modeling of two CoRoT solar analogues constrained by seismic and spectroscopic analysis.
- Author
-
Castro, M, Baudin, F, Benomar, O, Samadi, R, Morel, T, Barban, C, do Nascimento, J D, Lebreton, Y, Boumier, P, Marques, J P, and da Costa, J S
- Subjects
STELLAR evolution ,EVOLUTIONARY models ,AGE of stars ,ASTROPHYSICS ,SEISMIC networks ,PHYSICS - Abstract
Solar analogues are important stars to study for understanding the properties of the Sun. Combined with seismic and spectroscopic analysis, evolutionary modelling becomes a powerful method to characterize stellar intrinsic parameters, such as mass, radius, metallicity and age. However, these characteristics, relevant for other aspects of astrophysics or exoplanetary system physics, for example, are difficult to obtain with high precision and/or accuracy. The goal of this study is to characterize the two solar analogues, HD 42618 and HD 43587, observed by CoRoT. In particular, we aim to infer their precise mass, radius and age, using evolutionary modelling constrained by spectroscopic, photometric and seismic analysis. These stars show evidence of being older than the Sun but with a relatively large lithium abundance. We present the seismic analysis of HD 42618, and the modelling of the two solar analogues, HD 42618 and HD 43587 using the cestam stellar evolution code. Models were computed to reproduce the spectroscopic (effective temperature and metallicity) and seismic (mode frequency) data, and the luminosity of the stars, based on Gaia parallaxes. We infer very similar values of mass and radius for both stars compared with the literature, within the uncertainties, and we reproduce correctly the seismic constraints. The modelling shows that HD 42618 is slightly less massive and older than the Sun, and that HD 43587 is more massive and older than the Sun, in agreement with previous results. The use of chemical clocks improves the reliability of our age estimates. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
8. PBjam: A Python Package for Automating Asteroseismology of Solar-like Oscillators.
- Author
-
Nielsen, M. B., Davies, G. R., Ball, W. H., Lyttle, A. J., Li, T., Hall, O. J., Chaplin, W. J., Gaulme, P., Carboneau, L., Ong, J. M. J., García, R. A., Mosser, B., Roxburgh, I. W., Corsaro, E., Benomar, O., Moya, A., and Lund, M. N.
- Published
- 2021
- Full Text
- View/download PDF
9. On the uncertain nature of the core of $\boldsymbol{\alpha}$ Cen A
- Author
-
Bazot, M., Christensen-Dalsgaard, J., Gizon, L., and Benomar, O.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
High-quality astrometric, spectroscopic, interferometric and, importantly, asteroseismic observations are available for $\alpha$ Cen A, which is the closest binary star system to earth. Taking all these constraints into account, we study the internal structure of the star by means of theoretical modelling. Using the Aarhus STellar Evolution Code (ASTEC) and the tools of Computational Bayesian Statistics, in particular a Markov chain Monte Carlo algorithm, we perform statistical inferences for the physical characteristics of the star. We find that $\alpha$ Cen A has a probability of approximately 40% of having a convective core. This probability drops to few percents if one considers reduced rates for the $^{14}$N(p,$\gamma$)$^{15}$O reaction. These convective cores have fractional radii less than 8% when overshoot is neglected. Including overshooting also leads to the possibility of a convective core mostly sustained by the ppII chain energy output. We finally show that roughly 30% of the stellar models describing $\alpha$ Cen A are in the subgiant regime., Comment: 17 pages, 7 figures, accepted for publication in MNRAS
- Published
- 2016
10. Asteroseismology of solar-type stars with K2
- Author
-
Chaplin, W. J., Lund, M. N., Handberg, R., Basu, S., Buchhave, L. A., Campante, T. L., Davies, G. R., Huber, D., Latham, D. W., Latham, C. A., Serenelli, A., Antia, H. M., Appourchaux, T., Ball, W. H., Benomar, O., Casagrande, L., Christensen-Dalsgaard, J., Coelho, H. R., Creevey, O. L., Elsworth, Y., Garc, R. A., Gaulme, P., Hekker, S., Kallinger, T., Karoff, C., Kawaler, S. D., Kjeldsen, H., Lundkvist, M. S., Marcadon, F., Mathur, S., Miglio, A., Mosser, B., R, C., Roxburgh, I. W., Aguirre, V. Silva, Stello, D., Verma, K., White, T. R., Bedding, T. R., Barclay, T., Buzasi, D. L., Deheuvels, S., Gizon, L., Houdek, G., Howell, S. B., Salabert, D., and Soderblom, D. R.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,FOS: Physical sciences ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
We present the first detections by the NASA K2 Mission of oscillations in solar-type stars, using short-cadence data collected during K2 Campaign\,1 (C1). We understand the asteroseismic detection thresholds for C1-like levels of photometric performance, and we can detect oscillations in subgiants having dominant oscillation frequencies around $1000\,\rm \mu Hz$. Changes to the operation of the fine-guidance sensors are expected to give significant improvements in the high-frequency performance from C3 onwards. A reduction in the excess high-frequency noise by a factor of two-and-a-half in amplitude would bring main-sequence stars with dominant oscillation frequencies as high as ${\simeq 2500}\,\rm \mu Hz$ into play as potential asteroseismic targets for K2., Comment: Accepted for publication in PASP; 16 pages, 2 figures
- Published
- 2015
11. Latitudinal differential rotation in the solar analogues 16 Cygni A and B.
- Author
-
Bazot, M., Benomar, O., Christensen-Dalsgaard, J., Gizon, L., Hanasoge, S., Nielsen, M., Petit, P., and Sreenivasan, K. R.
- Subjects
- *
STELLAR rotation , *MICROWAVE spectroscopy , *FREQUENCIES of oscillating systems , *ACOUSTIC models , *POWER spectra ,ROTATION of the Sun - Abstract
Context. Asteroseismology has undergone a profound transformation as a scientific field following the CoRoT and Kepler space missions. The latter is now yielding the first measurements of latitudinal differential rotation obtained directly from oscillation frequencies. Differential rotation is a fundamental mechanism of the stellar dynamo effect. Aims. Our goal is to measure the amount of differential rotation in the solar analogues 16 Cyg A and B, which are the components of a binary system. These stars are the brightest observed by Kepler and have therefore been extensively observed, with exquisite precision on their oscillation frequencies. Methods. We modelled the acoustic power spectrum of 16 Cyg A and B using a model that takes into account the contribution of differential rotation to the rotational frequency splitting. The estimation was carried out in a Bayesian setting. We then inverted these results to obtain the rotation profile of both stars under the assumption of a solar-like functional form. Results. We observe that the magnitude of latitudinal differential rotation has a strong chance of being solar-like for both stars, their rotation rates being higher at the equator than at the pole. The measured latitudinal differential rotation, defined as the difference of rotation rate between the equator and the pole, is 320 ± 269 nHz and 440−383+363 440 − 383 + 363 $ 440^{+363}_{-383} $ nHz for 16 Cyg A and B, respectively, confirming that the rotation rates of these stars are almost solar-like. Their equatorial rotation rates are 535 ± 75 nHz and 565−129+150 565 − 129 + 150 $ 565_{-129}^{+150} $ nHz. Our results are in good agreement with measurements obtained from spectropolarimetry, spectroscopy, and photometry. Conclusions. We present the first conclusive measurement of latitudinal differential rotation for solar analogues. Their rotational profiles are very close to those of the Sun. These results depend weakly on the uncertainties of the stellar parameters. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
12. Fast Rotating Solar-like Stars Using Asteroseismic Datasets
- Author
-
García, R.A., Ceillier, T., Campante, T.L., Davies, G.R., Mathur, S., Suárez, J.C., Ballot, J., Benomar, O., Bonanno, A., Brun, A.S., Chaplin, W.J., Christensen-Dalsgaard, J., Deheuvels, S., Elsworth, Y., Handberg, R., Hekker, S., Jiménez, A., Karoff, C., Kjeldsen, H., Mathis, S., Mosser, B., Pallé, P.L., Pinsonneault, M., Régulo, C., Salabert, D., Silva Aguirre, V., Stello, D., Thompson, M.J., Verner, G., Shibahashi, H., Takata, M., Lynas-Gray, A.E., and Low Energy Astrophysics (API, FNWI)
- Subjects
Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics - Abstract
The NASA Kepler mission is providing an unprecedented set of asteroseismic data. In particular, short-cadence light-curves (˜ 60 s samplings), allow us to study solar-like stars covering a wide range of masses, spectral types and evolutionary stages. Oscillations have been observed in around 600 out of 2000 stars observed for one month during the survey phase of the Kepler mission. The measured light curves can present features related to the surface magnetic activity (starspots) and, thus we are able to obtain a good estimate of the surface (differential) rotation. In this work we establish the basis of such research and we show a potential method to find stars with fast surface rotation.
- Published
- 2012
13. Seismic analysis of four solar-like stars observed during more than eight months by Kepler
- Author
-
Mathur, S., L. Campante, T., Handberg, R., A. Garcia, R., Appourchaux, T., R. Bedding, T., Mosser, B., J. Chaplin, W., Ballot, J., Benomar, O., Bonanno, A., Corsaro, E., Gaulme, P., Hekker, S., Regulo, C., Salabert, D., Verner, G., R. White, T., M. Brandao, I., L. Creevey, O., Dogan, G., Bazot, M., S. Cunha, M., Elsworth, Y., Huber, D., J. Hale, S., Houdek, G., Karoff, C., Lundkvist, M., S. Metcalfe, T., Molenda-Zakowicz, J., J. P. F. G. Monteiro, M., J. Thompson, M., Stello, D., Christensen-Dalsgaard, J., L. Gilliland, R., D. Kawaler, S., Kjeldsen, H., D. Clarke, B., R. Girouard, F., R. Hall, J., V. Quintana, E., T. Sanderfer, D., and E. Seader, S.
- Subjects
astro-ph.SR - Abstract
Having started science operations in May 2009, the Kepler photometer has been able to provide exquisite data of solar-like stars. Five out of the 42 stars observed continuously during the survey phase show evidence of oscillations, even though they are rather faint (magnitudes from 10.5 to 12). In this paper, we present an overview of the results of the seismic analysis of 4 of these stars observed during more than eight months.
- Published
- 2011
14. Fast Rotating solar-like stars using asteroseismic datasets
- Author
-
A. García, R., Ceillier, T., Campante, T., R. Davies, G., Mathur, S., C Suarez, J., Ballot, J., Benomar, O., Bonanno, A., S. Brun, A., J. Chaplin, W., Christensen-Dalsgaard, J., Deheuvels, S., Elsworth, Y., Handberg, R., Hekker, S., Jimenez, A., Karoff, C., Kjeldsen, H., Mathis, S., Mosser, B., L. Palle, P., Pinsonneault, M., Regulo, C., Salabert, D., Aguirre, Victor Silva, Stello, D., J. Thompson, M., Verner, G., and PE11 team of Kepler WG1, the
- Subjects
astro-ph.SR ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics - Abstract
The NASA Kepler mission is providing an unprecedented set of asteroseismic data. In particular, short-cadence lightcurves (~60s samplings), allow us to study solar-like stars covering a wide range of masses, spectral types and evolutionary stages. Oscillations have been observed in around 600 out of 2000 stars observed for one month during the survey phase of the Kepler mission. The measured light curves can present features related to the surface magnetic activity (starspots) and, thus we are able to obtain a good estimation of the surface (differential) rotation. In this work we establish the basis of such research and we show a potential method to find stars with fast surface rotations.
- Published
- 2011
15. The CoRoT target HD 49933: 2- Comparison of theoretical mode amplitudes with observations
- Author
-
Samadi, R., Ludwig, H. -G., Belkacem, K., Goupil, M. J., Benomar, O., Mosser, B., Dupret, M. -A., Baudin, F., Appourchaux, T., and Michel, E.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,FOS: Physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
From the seismic data obtained by CoRoT for the star HD 49933 it is possible, as for the Sun, to constrain models of the excitation of acoustic modes by turbulent convection. We compare a stochastic excitation model described in Paper I (arXiv:0910.4027) with the asteroseismology data for HD 49933, a star that is rather metal poor and significantly hotter than the Sun. Using the mode linewidths measured by CoRoT for HD 49933 and the theoretical mode excitation rates computed in Paper I, we derive the expected surface velocity amplitudes of the acoustic modes detected in HD 49933. Using a calibrated quasi-adiabatic approximation relating the mode amplitudes in intensity to those in velocity, we derive the expected values of the mode amplitude in intensity. Our amplitude calculations are within 1-sigma error bars of the mode surface velocity spectrum derived with the HARPS spectrograph. The same is found with the mode amplitudes in intensity derived for HD 49933 from the CoRoT data. On the other hand, at high frequency, our calculations significantly depart from the CoRoT and HARPS measurements. We show that assuming a solar metal abundance rather than the actual metal abundance of the star would result in a larger discrepancy with the seismic data. Furthermore, calculations that assume the ``new'' solar chemical mixture are in better agreement with the seismic data than those that assume the ``old'' solar chemical mixture. These results validate, in the case of a star significantly hotter than the Sun and Alpha Cen A, the main assumptions in the model of stochastic excitation. However, the discrepancies seen at high frequency highlight some deficiencies of the modelling, whose origin remains to be understood., 8 pages, 3 figures (B-W and color), accepted for publication in Astronomy & Astrophysics. Corrected typo in Eq. (4). Updated references. Language improvements
- Published
- 2009
16. Session2A: MODES − Extracting eigenmode frequencies. Veröffentlichungen der Kommission für Astronomie|Communications in Asteroseismology|Communications in Asteroseismology 157 157
- Author
-
Bakos, G. Á., Kovács, G., Rovithis-Livaniou, H., Jerzykiewicz, M., Tarrant, N.J., Benomar, O., Tsantilas, S., Chaplin, W.J., and Elsworth, Y.P.
- Subjects
Mathematics, Physics and Space Research - Published
- 2009
17. Kepler observations of the asteroseismic binary HD 176465.
- Author
-
White, T. R., Benomar, O., Aguirre, V. Silva, Ball, W. H., Bedding, T. R., Chaplin, W. J., Christensen-Dalsgaard, J., Garcia, R. A., Gizon, L., Stello, D., Aigrain, S., Antia, H. M., Appourchaux, T., Bazot, M., Campante, T. L., Creevey, O. L., Davies, G. R., Elsworth, Y. P., Gaulme, P., and Handberg, R.
- Subjects
- *
BINARY stars , *STELLAR evolution , *STELLAR oscillations , *STAR formation - Abstract
Binary star systems are important for understanding stellar structure and evolution, and are especially useful when oscillations can be detected and analysed with asteroseismology. However, only four systems are known in which solar-like oscillations are detected in both components. Here, we analyse the fifth such system, HD 176465, which was observed by Kepler. We carefully analysed the system's power spectrum to measure individual mode frequencies, adapting our methods where necessary to accommodate the fact that both stars oscillate in a similar frequency range. We also modelled the two stars independently by fitting stellar models to the frequencies and complementary parameters. We are able to cleanly separate the oscillation modes in both systems. The stellar models produce compatible ages and initial compositions for the stars, as is expected from their common and contemporaneous origin. Combining the individual ages, the system is about 3:0 ± 0:5 Gyr old. The two components of HD 176465 are young physicallysimilar oscillating solar analogues, the first such system to be found, and provide important constraints for stellar evolution and asteroseismology. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
18. On the uncertain nature of the core of α Cen A.
- Author
-
Bazot, M., Christensen-Dalsgaard, J., Gizon, L., and Benomar, O.
- Subjects
ASTROMETRIC telescopes ,SPECTROSCOPIC imaging ,BINARY stars ,BAYESIAN analysis ,MARKOV chain Monte Carlo - Abstract
High-quality astrometric, spectroscopic, interferometric and, importantly, asteroseismic observations are available for α Cen A, which is the closest binary star system to earth. Taking all these constraints into account, we study the internal structure of the star by means of theoretical modelling. Using the Aarhus STellar Evolution Code (ASTEC) and the tools of Computational Bayesian Statistics, in particular a Markov chain Monte Carlo algorithm, we perform statistical inferences for the physical characteristics of the star. We find that α Cen A has a probability of approximately 40 per cent of having a convective core. This probability drops to few per cent if one considers reduced rates for the
14 N(p,γ )15 O reaction. These convective cores have fractional radii less than 8 per cent when overshoot is neglected. Including overshooting also leads to the possibility of a convective core mostly sustained by the ppII chain energy output. We finally show that roughly 30 per cent of the stellar models describing α Cen A are in the subgiant regime. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
19. Oscillation frequencies for 35 Kepler solar-type planet-hosting stars using Bayesian techniques and machine learning.
- Author
-
Davies, G. R., Aguirre, V. Silva, Bedding, T. R., Handberg, R., Lund, M. N., Chaplin, W. J., Huber, D., White, T. R., Benomar, O., Hekker, S., Basu, S., Campante, T. L., Christensen-Dalsgaard, J., Elsworth, Y., Karoff, C., Kjeldsen, H., Lundkvist, M. S., Metcalfe, T. S., and Stello, D.
- Subjects
OSCILLATIONS ,BAYESIAN analysis ,SEISMOLOGY ,MACHINE learning - Abstract
Kepler has revolutionized our understanding of both exoplanets and their host stars. Asteroseismology is a valuable tool in the characterization of stars and Kepler is an excellent observing facility to perform asteroseismology. Here we select a sample of 35 Kepler solar-type stars which host transiting exoplanets (or planet candidates) with detected solar-like oscillations. Using available Kepler short cadence data up to Quarter 16 we create power spectra optimized for asteroseismology of solar-type stars. We identify modes of oscillation and estimate mode frequencies by 'peak bagging' using a Bayesian Markov Chain Monte Carlo framework. In addition, we expand the methodology of quality assurance using a Bayesian unsupervised machine learning approach. We report the measured frequencies of the modes of oscillation for all 35 stars and frequency ratios commonly used in detailed asteroseismic modelling. Due to the high correlations associated with frequency ratios we report the covariance matrix of all frequencies measured and frequency ratios calculated. These frequencies, frequency ratios, and covariance matrices can be used to obtain tight constraint on the fundamental parameters of these planet-hosting stars. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
20. Nearly uniform internal rotation of solar-like main-sequence stars revealed by space-based asteroseismology and spectroscopic measurements.
- Author
-
Benomar, O., Takata, M., Shibahashi, H., Ceillier, T., and García, R. A.
- Subjects
- *
ASTEROSEISMOLOGY , *STELLAR spectra , *STELLAR mass , *STELLAR rotation , *ANGULAR momentum (Nuclear physics) - Abstract
The rotation rates in the deep interior and at the surface of 22 main-sequence stars with masses between 1.0 and 1.6M are constrained by combining asteroseismological analysis with spectroscopic measurements. The asteroseismic data of each star are taken by the Kepler or CoRoT space mission. It is found that the difference between the surface rotation rate and the average rotation rate (excluding the convective core) of most of stars is small enough to suggest that an efficient process of angular momentum transport operates during and/or before the main-sequence stage of stars. If each of the surface convective zone and the underlying radiative zone, for individual stars, is assumed to rotate uniformly, the difference in the rotation rate between the two zones turns out to be no more than a factor of 2 in most of the stars independently of their ages. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
21. Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni.
- Author
-
Davies, G. R., Chaplin, W. J., Farr, W. M., García, R. A., Lund, M. N., Mathis, S., Metcalfe, T. S., Appourchaux, T., Basu, S., Benomar, O., Campante, T. L., Ceillier, T., Elsworth, Y., Handberg, R., Salabert, D., and Stello, D.
- Subjects
STELLAR rotation ,SEISMOLOGY ,PLANETARY surfaces ,P Cygni stars ,STELLAR oscillations - Abstract
The solar analogues 16 Cyg A and B are excellent asteroseismic targets in the Kepler field of view and together with a red dwarf and a Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation with the current Kepler data but instead use the technique of asteroseimology to determine rotational properties of both 16 Cyg A and B. We find the rotation periods to be 23.8
-1.8 +1.5 and 23.2-3.2 +11.5 d, and the angles of inclination to be 56-5 +6 ° and 36-7 +17 °, for A and B, respectively. Together with these results we use the published mass and age to suggest that, under the assumption of a solar-like rotation profile, 16 Cyg A could be used when calibrating gyrochronology relations. In addition, we discuss the known 16 Cyg B star-planet eccentricity and measured low obliquity which is consistent with Kozai cycling and tidal theory. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
22. Successful Asteroseismology for a Better Characterization of the Exoplanet HAT-P-7b.
- Author
-
Oshagh, M., Grigahcène, A., Benomar, O., Dupret, M.-A., Monteiro, M. J. P. F. G., Scuflaire, R., and Santos, N. C.
- Published
- 2013
- Full Text
- View/download PDF
23. Oscillation mode linewidths and heights of 23 main-sequence stars observed by Kepler.
- Author
-
Appourchaux, T., Antia, H. M., Benomar, O., Campante, T. L., Davies, G. R., Handberg, R., Howe, R., Régulo, C., Belkacem, K., Houdek, G., García, R. A., and Chaplin, W. J.
- Subjects
SOLAR oscillations ,BAYESIAN analysis ,INTERIOR of stars - Abstract
Context. Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe the stars using asteroseismology. Aims. We provide the mode linewidths and mode heights of the oscillations of various stars as a function of frequency and of effective temperature. Methods. We used a time series of nearly two years of data for each star. The 23 stars observed belong to the simple or F-like category. The power spectra of the 23 main-sequence stars were analysed using both maximum likelihood estimators and Bayesian estimators, providing individual mode characteristics such as frequencies, linewidths, and mode heights. We study the source of systematic errors in the mode linewidths and mode heights, and we present a way to correct these errors with respect to a common reference fit. Results. Using the correction, we can explain all sources of systematic errors, which could be reduced to less than ±15% for mode linewidths and heights, and less than ±5% for amplitude, when compared to the reference fit. The effect of a different estimated stellar background and a different estimated splitting will provide frequency-dependent systematic errors that might affect the comparison with theoretical mode linewidth and mode height, therefore affecting the understanding of the physical nature of these parameters. All other sources of relative systematic errors are less dependent upon frequency. We also provide the dependence of the so-called linewidth dip in the middle of the observed frequency range as a function of effective temperature. We show that the depth of the dip decreases with increasing effective temperature. The dependence of the dip on effective temperature may imply that the mixing length parameter a or the convective flux may increase with effective temperature. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
24. Seismic analysis of HD 43587Aa, a solar-like oscillator in a multiple system.
- Author
-
Boumier, P., Benomar, O., Baudin, F., Verner, G., Appourchaux, T., Lebreton, Y., Gaulme, P., Chaplin, W., García, R. A., Hekker, S., Regulo, C., Salabert, D., Stahn, T., Elsworth, Y., Gizon, L., Hall, M., Mathur, S., Michel, E., Morel, T., and Mosser, B.
- Subjects
- *
SEISMIC prospecting , *MULTIPLE scattering (Physics) , *BINARY stars , *MARKOV chain Monte Carlo , *STELLAR mass , *SOLAR flares - Abstract
Context. The object HD43587Aa is a G0V star observed during the 145-day LRa03 run of the COnvection, ROtation and planetary Transits space mission (CoRoT), for which complementary High Accuracy Radial velocity Planet Searcher (HARPS) spectra with S/N > 300 were also obtained. Its visual magnitude is 5.71, and its effective temperature is close to 5950 K. It has a known companion in a highly eccentric orbit and is also coupled with two more distant companions. Aims. We undertake a preliminary investigation of the internal structure of HD43587Aa. Methods. We carried out a seismic analysis of the star, using maximum likelihood estimators and Markov chainMonte Carlo methods. Results. We established the first table of the eigenmode frequencies, widths, and heights for HD43587Aa. The star appears to have a mass and a radius slightly larger than the Sun, and is slightly older (5.6 Gyr). Two scenarios are suggested for the geometry of the star: either its inclination angle is very low, or the rotation velocity of the star is very low. Conclusions. A more detailed study of the rotation and of the magnetic and chromospheric activity for this star is needed, and will be the subject of a further study. New high resolution spectrometric observations should be performed for at least several months in duration. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
25. Seismic constraints on the radial dependence of the internal rotation profiles of six Kepler subgiants and young red giants.
- Author
-
Deheuvels, S., Doğan, G., Goupil, M. J., Appourchaux, T., Benomar, O., Bruntt, H., Campante, T. L., Casagrande, L., Ceillier, T., Davies, G. R., De Cat, P., Fu, J. N., García, R. A., Lobel, A., Mosser, B., Reese, D.R., Regulo, C., Schou, J., Stahn, T., and Thygesen, A. O.
- Subjects
CONSTRAINTS (Physics) ,SEISMIC prospecting ,KEPLER'S equation ,SUBGIANT stars ,STELLAR evolution - Abstract
Context. We still do not understand which physical mechanisms are responsible for the transport of angular momentum inside stars. The recent detection of mixed modes that contain the clear signature of rotation in the spectra of Kepler subgiants and red giants gives us the opportunity to make progress on this question. Aims. Our aim is to probe the radial dependence of the rotation profiles for a sample of Kepler targets. For this purpose, subgiants and early red giants are particularly interesting targets because their rotational splittings are more sensitive to the rotation outside the deeper core than is the case for their more evolved counterparts. Methods. We first extracted the rotational splittings and frequencies of the modes for six young Kepler red giants. We then performed a seismic modeling of these stars using the evolutionary codes CESAM2K and astec. By using the observed splittings and the rotational kernels of the optimal models, we inverted the internal rotation profiles of the six stars. Results. We obtain estimates of the core rotation rates for these stars, and upper limits to the rotation in their convective envelope. We show that the rotation contrast between the core and the envelope increases during the subgiant branch. Our results also suggest that the core of subgiants spins up with time, while their envelope spins down. For two of the stars, we show that a discontinuous rotation profile with a deep discontinuity reproduces the observed splittings significantly better than a smooth rotation profile. Interestingly, the depths that are found to be most probable for the discontinuities roughly coincide with the location of the H-burning shell, which separates the layers that contract from those that expand. Conclusions. We characterized the differential rotation pattern of six young giants with a range of metallicities, and with both radiative and convective cores on the main sequence. This will bring observational constraints to the scenarios of angular momentum transport in stars. Moreover, if the existence of sharp gradients in the rotation profiles of young red giants is confirmed, it is expected to help in distinguishing between the physical processes that could transport angular momentum in the subgiant and red giant branches. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
26. Study of KIC 8561221 observed by Kepler: an early red giant showing depressed dipolar modes?
- Author
-
García, R. A., Hernández, F. Pérez, Benomar, O., Aguirre, V. Silva, Ballot, J., Davies, G. R., Doğan, G., Stello, D., Christensen-Dalsgaard, J., Houdek, G., Lignières, F., Mathur, S., Takata, M., Ceillier, T., Chaplin, W. J., Mathis, S., Mosser, B., Ouazzani, R. M., Pinsonneault, M. H., and Reese, D. R.
- Subjects
RED giants ,STELLAR structure ,STELLAR magnetic fields ,AMPLITUDE estimation - Abstract
Context. The continuous high-precision photometric observations provided by the CoRoT and Kepler space missions have allowed us to understand the structure and dynamics of red giants better using asteroseismic techniques. A small fraction of these stars show dipole modes with unexpectedly low amplitudes. The reduction in amplitude is more pronounced for stars with a higher frequency of maximum power, V
max . Aims. In this work we want to characterise KIC 8561221 in order to confirm that it is currently the least evolved star among this peculiar subset and to discuss several hypotheses that could help explain the reduction of the dipole mode amplitudes. Methods. We used Kepler short- and long-cadence data combined with spectroscopic observations to infer the stellar structure and dynamics of KIC 8561221. We then discussed different scenarios that could contribute to reducing the dipole amplitudes, such as a fast-rotating interior or the effect of a magnetic field on the properties of the modes. We also performed a detailed study of the inertia and damping of the modes. Results. We have been able to characterise 36 oscillations modes, in particular, a few dipole modes above Vmax that exhibit nearly normal amplitudes. The frequencies of all the measured modes were used to determine the overall properties and the internal structure of the star.We have inferred a surface rotation period of ~91 days and uncovered a variation in the surface magnetic activity during the last 4 years. The analysis of the convective background did not reveal any difference compared to "normal" red giants. As expected, the internal regions of the star probed by the ⨏ = 2 and 3 modes spin 4 to 8 times faster than the surface. Conclusions. With our grid of standard models we are able to properly fit the observed frequencies. Our model calculation of mode inertia and damping give no explanation for the depressed dipole modes. A fast-rotating core is also ruled out as a possible explanation. Finally, we do not have any observational evidence of a strong deep magnetic field inside the star. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
27. PROPERTIES OF OSCILLATION MODES IN SUBGIANT STARS OBSERVED BY KEPLER.
- Author
-
BENOMAR, O., BEDDING, T. R., MOSSER, B., STELLO, D., BELKACEM, K., GARCIA, R. A., WHITE, T. R., KUEHN, C. A., DEHEUVELS, S., and CHRISTENSEN-DALSGAARD, J.
- Subjects
- *
SUBGIANT stars , *GIANT stars , *PHYSICS , *OSCILLATIONS - Abstract
Mixed modes seen in evolved stars carry information on their deeper layers that can place stringent constraints on their physics and on their global properties (mass, age, etc.). In this study, we present a method to identify and measure all oscillatory mode characteristics (frequency, height, width). Analyzing four subgiant stars, we present the first measure of the effect of the degree of mixture on the l = 1 mixed mode characteristics. We also show that some stars have measurable l = 2 mixed modes and discuss the interest of their measure to constrain the deeper layers of stars. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
28. A Bayesian approach to scaling relations for amplitudes of solar-like oscillations in Kepler stars.
- Author
-
Corsaro, E., Fröhlich, H.-E., Bonanno, A., Huber, D., Bedding, T. R., Benomar, O., De Ridder, J., and Stello, D.
- Subjects
AMPLITUDE estimation ,SOLAR oscillations ,KEPLER problem ,GIANT stars ,POWER spectra ,BAYESIAN analysis - Abstract
We investigate different amplitude scaling relations adopted for the asteroseismology of stars that show solar-like oscillations. Amplitudes are among the most challenging asteroseismic quantities to handle because of the large uncertainties that arise in measuring the background level in the star's power spectrum. We present results computed by means of a Bayesian inference on a sample of 1640 stars observed with Kepler, spanning from main sequence to red giant stars, for 12 models used for amplitude predictions and exploiting recently well-calibrated effective temperatures from Sloan Digital Sky Survey photometry. We test the candidate amplitude scaling relations by means of a Bayesian model comparison. We find the model having a separate dependence upon the mass of the stars to be largely the most favoured one. The differences among models and the differences seen in their free parameters from early to late phases of stellar evolution are also highlighted. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
29. Solar-like oscillations in distant stars as seen by CoRoT : the special case of HD 42618, a solar sister.
- Author
-
Barban, C, Deheuvels, S, Goupil, M J, Lebreton, Y, Mathur, S, Michel, E, Morel, Th, Ballot, J, Baudin, F, Belkacem, K, Benomar, O, Boumier, P, Davies, G R, García, R A, Hall, M P, Mosser, B, Poretti, E, Régulo, C, Roxburgh, I, and Samadi, R
- Published
- 2013
- Full Text
- View/download PDF
30. Study of HD 169392A observed by CoRoT and HARPS.
- Author
-
Mathur, S., Bruntt, H., Catala, C., Benomar, O., Davies, G. R., García, R. A., Salabert, D., Ballot, J., Mosser, B., Régulo, C., Chaplin, W. J., Elsworth, Y., Handberg, R., Hekker, S., Mantegazza, L., Michel, E., Poretti, E., Rainer, M., Roxburgh, I. W., and Samadi, R.
- Subjects
COROTATING interaction regions ,INTERPLANETARY magnetic fields ,STAR observations ,STELLAR evolution ,STELLAR spectra ,STELLAR oscillations - Abstract
Context. The results obtained by asteroseismology with data from space missions such as CoRoT and Kepler are providing new insights into stellar evolution. After five years of observations, CoRoT is continuing to provide high-quality data and we here present an analysis of the CoRoT observations of the double star HD 169392, complemented by ground-based spectroscopic observations. Aims. This work aims at characterising the fundamental parameters of the two stars, their chemical composition, the acoustic-mode global parameters including their individual frequencies, and their dynamics. Methods. We analysed HARPS observations of the two stars to derive their chemical compositions. Several methods were used and compared to determine the global properties of stars' acoustic modes and their individual frequencies from the photometric data of CoRoT. Results. The new spectroscopic observations and archival astrometric values suggest that HD 169392 is a weakly bound wide binary system. We obtained spectroscopic parameters for both components which suggest that they originate from the same interstellar cloud. However, only the signature of oscillation modes of HD 169392 A was measured; the signal-to-noise ratio of the modes in HD 169392B is too low to allow any confident detection. For HD 169392 A we were able to extract parameters of modes for ℓ = 0, 1, 2, and 3. The analysis of splittings and inclination angle gives two possible solutions: one with with splittings and inclination angles of 0.4-1.0 μHz and 20-40°, the other with 0.2-0.5 μHz and 55-86°. Modelling this star using the Asteroseismic Modeling Portal (AMP) gives a mass of 1.15 ± 0:01 M
⊙ , a radius of 1.88 ± 0:02 R⊙ , and an age of 4.33 ± 0:12 Gyr. The uncertainties come from estimated errors on the observables but do not include uncertainties on the surface layer correction or the physics of stellar models. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
31. Oscillation mode frequencies of 61 main-sequence and subgiant stars observed by Kepler.
- Author
-
Appourchaux, T., Chaplin, W. J., García, R. A., Gruberbauer, M., Verner, G. A., Antia, H. M., Benomar, O., Campante, T. L., Davies, G. R., Deheuvels, S., Handberg, R., Hekker, S., Howe, R., Régulo, C., Salabert, D., Bedding, T. R., White, T. R., Ballot, J., Mathur, S., and Silva Aguirre, V.
- Subjects
OSCILLATIONS ,ASYMPTOTIC efficiencies ,STARS ,PITMAN'S measure of closeness ,METHODOLOGY - Abstract
Context. Solar-like oscillations have been observed by Kepler and CoRoT in several solar-type stars, thereby providing a way to probe the stars using asteroseismology Aims. We provide the mode frequencies of the oscillations of various stars required to perform a comparison with those obtained from stellar modelling. Methods. We used a time series of nine months of data for each star. The 61 stars observed were categorised in three groups: simple, F-like, and mixed-mode. The simple group includes stars for which the identification of the mode degree is obvious. The F-like group includes stars for which the identification of the degree is ambiguous. The mixed-mode group includes evolved stars for which the modes do not follow the asymptotic relation of low-degree frequencies. Following this categorisation, the power spectra of the 61 main-sequence and subgiant stars were analysed using both maximum likelihood estimators and Bayesian estimators, providing individual mode characteristics such as frequencies, linewidths, and mode heights. We developed and describe a methodology for extracting a single set of mode frequencies from multiple sets derived by different methods and individual scientists. We report on how one can assess the quality of the fitted parameters using the likelihood ratio test and the posterior probabilities. Results. We provide the mode frequencies of 61 stars (with their 1-σ error bars), as well as their associated échelle diagrams. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
32. A UNIFORM ASTEROSEISMIC ANALYSIS OF 22 SOLAR-TYPE STARS OBSERVED BY KEPLER.
- Author
-
MATHUR, S., METCALFE, T. S., WOITASZEK, M., BRUNTT, H., VERNER, G. A., CHRISTENSEN-DALSGAARD, J., CREEVEY, O. L., DOĞAN, G., BASU, S., KAROFF, C., STELLO, D., APPOURCHAUX, T., CAMPANTE, T. L., CHAPLIN, W. J., GARCÍA, R. A., BEDDING, T. R., BENOMAR, O., BONANNO, A., DEHEUVELS, S., and ELSWORTH, Y.
- Subjects
ASTEROSEISMOLOGY ,EXTRASOLAR planets ,STELLAR structure ,STELLAR mass ,STELLAR radiation - Abstract
Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure and evolution for the large sample of solar-type stars in the field. We perform a uniform analysis of 22 of the brightest asteroseismic targets with the highest signal-to- noise ratio observed for 1 month each during the first year of the mission, and we quantify the precision and relative accuracy of asteroseismic determinations of the stellar radius, mass, and age that are possible using various methods. We present the properties of each star in the sample derived from an automated analysis of the individual oscillation frequencies and other observational constraints using the Asteroseismic Modeling Portal (AMP), and we compare them to the results of model-grid-based methods that fit the global oscillation properties. We find that fitting the individual frequencies typically yields asteroseismic radii and masses to ~1% precision, and ages to ~2.5% precision (respectively, 2, 5, and 8 times better than fitting the global oscillation properties). The absolute level of agreement between the results from different approaches is also encouraging, with model-grid-based methods yielding slightly smaller estimates of the radius and mass and slightly older values for the stellar age relative to AMP, which computes a large number of dedicated models for each star. The sample of targets for which this type of analysis is possible will grow as longer data sets are obtained during the remainder of the mission. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
33. Acoustic spectrum fitting for a large set of solar-like pulsators.
- Author
-
Benomar, O., Baudin, F., Chaplin, W. J., Elsworth, Y., and Appourchaux, T.
- Subjects
- *
ACOUSTIC spectroscopy , *STELLAR structure , *SEISMOLOGY , *SOLAR radiation , *ASTROPHYSICS , *DATA analysis , *BAYESIAN analysis - Abstract
ABSTRACT Asteroseismology provides the means both to constrain the global properties and to probe the internal structures of stars. Asteroseismic data are now available on large numbers of solar-type stars, thanks in particular to the CoRoT and Kepler space missions, and automated data-analysis pipelines are needed to provide efficient and timely results. Here, we present an automated algorithm that is able to extract mode parameters under low signal-to-noise ratio conditions. We use a Bayesian framework to ensure the robustness of the algorithm. We discuss the efficiency of the method and test it using Variability of Solar Irradiance and Gravity Oscillations (VIRGO) Sun-as-a-star photometry data and the artificial Astero Fitting at Low Angular degree Group (asteroFLAG) Kepler ensemble. Analysis of the VIRGO data shows that it is possible to track variations of the individual mode parameters (frequency, height, width) through the solar cycle, using short time series (30 days). The present analysis also revealed a modulation of the degree l = 2 relative height through the solar cycle. Applied on asteroFLAG data, we show that the pipeline extracts accurately the central frequency and the large separation. It is also able to identify the degree of the modes in 78 per cent of stars. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
34. Oscillation mode linewidths of main-sequence and subgiant stars observed by Kepler.
- Author
-
Appourchaux, T., Benomar, O., Gruberbauer, M., Chaplin, W. J., García, R. A., Handberg, R., Verner, G. A., Antia, H. M., Campante, T. L., Davies, G. R., Deheuvels, S., Hekker, S., Howe, R., Salabert, D., Bedding, T. R., White, T. R., Houdek, G., Silva Aguirre, V., Elsworth, Y. P., and Van Cleve, J.
- Subjects
- *
SOLAR oscillations , *TEMPERATURE of stars , *SUBGIANT stars , *KEPLER'S laws , *PLANETARY theory - Abstract
Context. Solar-like oscillations have been observed by Kepler and CoRoT in several solar-type stars. Aims. We study the variations in the stellar p-mode linewidth as a function of effective temperature. Methods. We study a time series of nine months of Kepler data. We analyse the power spectra of 42 cool main-sequence stars and subgiants using both maximum likelihood estimators and Bayesian estimators to recover individual mode characteristics such as frequencies, linewidths, and mode heights. Results. We report on the mode linewidth at both maximum power and maximum mode height for these 42 stars as a function of effective temperature. Conclusions. We show that the mode linewidth at either maximum mode height or maximum amplitude follows a scaling relation with effective temperature, which is a combination of a power law and a lower bound. The typical power-law index is about 13 for the linewidth derived from the maximum mode height, and about 16 for the linewidth derived from the maximum amplitude, while the lower bound is about 0.3 μHz and 0.7 μHz, respectively. We stress that this scaling relation is only valid for cool main-sequence stars and subgiants, and does not have any predictive power outside the temperature range of these stars. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
35. SOLAR-LIKE OSCILLATIONS IN KIC 11395018 AND KIC 11234888 FROM 8 MONTHS OF KEPLER DATA.
- Author
-
MATHUR, S., HANDBERG, R., CAMPANTE, T. L., GARCIA, R. A., APPOURCHAUX, T., BEDDING, T. R., MOSSER, B., CHAPLIN, W. J., BALLOT, J., BENOMAR, O., BONANNO, A., CORSARO, E., GAULME, P., HEKKER, S., RÉGULO, C., SALABERT, D., VERNER, G., WHITE, T. R., BRANDÃO, I. M., and CREEVEY, O. L.
- Subjects
SOLAR oscillations ,SIGNAL-to-noise ratio ,STELLAR rotation ,SPECTRAL energy distribution ,RADIAL bone ,SCALING laws (Statistical physics) - Abstract
We analyze the photometric short-cadence data obtained with the Kepler mission during the first 8 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 (S/N) compared with 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 line width 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 S/N 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 is obtained using the scaling laws. We emphasize the importance of continued observations for the stars with low S/N 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. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
36. PROPERTIES OF 42 SOLAR-TYPE KEPLER TARGETS FROM THE ASTEROSEISMIC MODELING PORTAL.
- Author
-
Metcalfe, T. S., Creevey, O. L., Doğan, G., Mathur, S., Xu, H., Bedding, T. R., Chaplin, W. J., Christensen-Dalsgaard, J., Karoff, C., Trampedach, R., Benomar, O., Brown, B. P., Buzasi, D. L., Campante, T. L., Çelik, Z., Cunha, M. S., Davies, G. R., Deheuvels, S., Derekas, A., and Mauro, M. P. Di
- Published
- 2014
- Full Text
- View/download PDF
37. ASTEROSEISMOLOGY OF EVOLVED STARS WITH KEPLER: A NEW WAY TO CONSTRAIN STELLAR INTERIORS USING MODE INERTIAS.
- Author
-
Benomar, O., Belkacem, K., Bedding, T. R., Stello, D., Mauro, M. P. Di, Ventura, R., Mosser, B., Goupil, M. J., Samadi, R., and Garcia, R. A.
- Published
- 2014
- Full Text
- View/download PDF
38. SEISMIC EVIDENCE FOR A RAPIDLY ROTATING CORE IN A LOWER-GIANT-BRANCH STAR OBSERVED WITH KEPLER.
- Author
-
Deheuvels, S., García, R. A., Chaplin, W. J., Basu, S., Antia, H. M., Appourchaux, T., Benomar, O., Davies, G. R., Elsworth, Y., Gizon, L., Goupil, M. J., Reese, D. R., Regulo, C., Schou, J., Stahn, T., Casagrande, L., Christensen-Dalsgaard, J., Fischer, D., Hekker, S., and Kjeldsen, H.
- Subjects
STARS ,SPACE vehicles ,STELLAR rotation ,ANGULAR momentum (Nuclear physics) ,SOLAR research - Abstract
Rotation is expected to have an important influence on the structure and the evolution of stars. However, the mechanisms of angular momentum transport in stars remain theoretically uncertain and very complex to take into account in stellar models. To achieve a better understanding of these processes, we desperately need observational constraints on the internal rotation of stars, which until very recently was restricted to the Sun. In this paper, we report the detection of mixed modes—i.e., modes that behave both as g modes in the core and as p modes in the envelope—in the spectrum of the early red giant KIC 7341231, which was observed during one year with the Kepler spacecraft. By performing an analysis of the oscillation spectrum of the star, we show that its non-radial modes are clearly split by stellar rotation and we are able to determine precisely the rotational splittings of 18 modes. We then find a stellar model that reproduces very well the observed atmospheric and seismic properties of the star. We use this model to perform inversions of the internal rotation profile of the star, which enables us to show that the core of the star is rotating at least five times faster than the envelope. This will shed new light on the processes of transport of angular momentum in stars. In particular, this result can be used to place constraints on the angular momentum coupling between the core and the envelope of early red giants, which could help us discriminate between the theories that have been proposed over the last few decades. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
39. Open issues in probing interiors of solar-like oscillating main sequence stars: 2. Diversity in the HR diagram.
- Author
-
Goupil, M. J., Lebreton, Y., Marques, J. P., Deheuvels, S., Benomar, O., and Provost, J.
- Published
- 2011
- Full Text
- View/download PDF
40. Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi
- Author
-
William J. Chaplin, Aldo M. Serenelli, Andrea Miglio, Thierry Morel, J. Ted Mackereth, Fiorenzo Vincenzo, Hans Kjeldsen, Sarbani Basu, Warrick H. Ball, Amalie Stokholm, Kuldeep Verma, Jakob Rørsted Mosumgaard, Victor Silva Aguirre, Anwesh Mazumdar, Pritesh Ranadive, H. M. Antia, Yveline Lebreton, Joel Ong, Thierry Appourchaux, Timothy R. Bedding, Jørgen Christensen-Dalsgaard, Orlagh Creevey, Rafael A. García, Rasmus Handberg, Daniel Huber, Steven D. Kawaler, Mikkel N. Lund, Travis S. Metcalfe, Keivan G. Stassun, Michäel Bazot, Paul G. Beck, Keaton J. Bell, Maria Bergemann, Derek L. Buzasi, Othman Benomar, Diego Bossini, Lisa Bugnet, Tiago L. Campante, Zeynep Çelik Orhan, Enrico Corsaro, Lucía González-Cuesta, Guy R. Davies, Maria Pia Di Mauro, Ricky Egeland, Yvonne P. Elsworth, Patrick Gaulme, Hamed Ghasemi, Zhao Guo, Oliver J. Hall, Amir Hasanzadeh, Saskia Hekker, Rachel Howe, Jon M. Jenkins, Antonio Jiménez, René Kiefer, James S. Kuszlewicz, Thomas Kallinger, David W. Latham, Mia S. Lundkvist, Savita Mathur, Josefina Montalbán, Benoit Mosser, Andres Moya Bedón, Martin Bo Nielsen, Sibel Örtel, Ben M. Rendle, George R. Ricker, Thaíse S. Rodrigues, Ian W. Roxburgh, Hossein Safari, Mathew Schofield, Sara Seager, Barry Smalley, Dennis Stello, Róbert Szabó, Jamie Tayar, Nathalie Themeßl, Alexandra E. L. Thomas, Roland K. Vanderspek, Walter E. van Rossem, Mathieu Vrard, Achim Weiss, Timothy R. White, Joshua N. Winn, Mutlu Yıldız, European Commission, European Research Council, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Generalitat de Catalunya, Chaplin W.J., Serenelli A.M., Miglio A., Morel T., Mackereth J.T., Vincenzo F., Kjeldsen H., Basu S., Ball W.H., Stokholm A., Verma K., Mosumgaard J.R., Silva Aguirre V., Mazumdar A., Ranadive P., Antia H.M., Lebreton Y., Ong J., Appourchaux T., Bedding T.R., Christensen-Dalsgaard J., Creevey O., Garcia R.A., Handberg R., Huber D., Kawaler S.D., Lund M.N., Metcalfe T.S., Stassun K.G., Bazot M., Beck P.G., Bell K.J., Bergemann M., Buzasi D.L., Benomar O., Bossini D., Bugnet L., Campante T.L., Orhan Z.C., Corsaro E., Gonzalez-Cuesta L., Davies G.R., Di Mauro M.P., Egeland R., Elsworth Y.P., Gaulme P., Ghasemi H., Guo Z., Hall O.J., Hasanzadeh A., Hekker S., Howe R., Jenkins J.M., Jimenez A., Kiefer R., Kuszlewicz J.S., Kallinger T., Latham D.W., Lundkvist M.S., Mathur S., Montalban J., Mosser B., Bedon A.M., Nielsen M.B., Ortel S., Rendle B.M., Ricker G.R., Rodrigues T.S., Roxburgh I.W., Safari H., Schofield M., Seager S., Smalley B., Stello D., Szabo R., Tayar J., Themessl N., Thomas A.E.L., Vanderspek R.K., van Rossem W.E., Vrard M., Weiss A., White T.R., Winn J.N., Yildiz M., Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Psychology, St John's University, Institute of Space Sciences [Barcelona] (ICE-CSIC), Spanish National Research Council [Madrid] (CSIC), School of Physics and Astronomy, University of Birmingham [Birmingham], Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Danish AsteroSeismology Centre (DASC), Aarhus University [Aarhus], Department of Astronomy, Yale University [New Haven], Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-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), 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), 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), Sydney Institute for Astronomy (SIfA), The University of Sydney, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), 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], University of Iowa [Iowa City], 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), Istituto di Astrofisica Spaziale e Fisica cosmica - Roma (IASF-Roma), Istituto Nazionale di Astrofisica (INAF), 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), NASA Ames Research Center (ARC), Centre for Automation and Robotics (CAR), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad Politécnica de Madrid (UPM), Kiepenheuer-Institut für Sonnenphysik (KIS), Stellar Astrophysics Centre [Aarhus] (SAC), Instituut voor Sterrenkunde [Leuven], Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven), High Altitude Observatory (HAO), National Center for Atmospheric Research [Boulder] (NCAR), Département des Sciences et Gestion de l'Environnement/Océanologie [Liège], Université de Liège, Center for Space Research [Cambridge] (CSR), Massachusetts Institute of Technology (MIT), High Speed Networks Laboratory, Dept. of Telecommunications and Media Informatics, Budapest University of Technology and Economics [Budapest] (BME), Department of Astronomy (Ohio State University), Ohio State University [Columbus] (OSU), Observatoire de Paris, Université Paris sciences et lettres (PSL), Ege Üniversitesi, CERFACS [Toulouse], 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 (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), 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), Universidad Politécnica de Madrid (UPM)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), PSL Research University (PSL), 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), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, and 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)
- Subjects
010504 meteorology & atmospheric sciences ,Milky Way ,Population ,GAIA ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,MASS ,CHEMICAL-COMPOSITION ,Q1 ,01 natural sciences ,Asteroseismology ,0103 physical sciences ,QB460 ,Satellite galaxy ,STELLAR HALOES ,Astrophysics::Solar and Stellar Astrophysics ,10. No inequality ,education ,010303 astronomy & astrophysics ,QB600 ,QC ,Astrophysics::Galaxy Astrophysics ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Dwarf galaxy ,QB ,Physics ,[PHYS]Physics [physics] ,education.field_of_study ,[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] ,ACCRETION HISTORY ,Astronomy and Astrophysics ,DISC ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,MODEL ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,DARK-MATTER HALOES ,ROTATION ,Halo ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,SOLAR-LIKE OSCILLATIONS ,QB799 - Abstract
This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). et al., Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. Although these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to date precisely the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called Gaia–Enceladus, leading to substantial pollution of the chemical and dynamical properties of the Milky Way. Here we identify the very bright, naked-eye star ν Indi as an indicator of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be 11.0±0.7 (stat) ±0.8 (sys) billion years. The star bears hallmarks consistent with having been kinematically heated by the Gaia–Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 billion years ago, at 68% and 95% confidence, respectively. Computations based on hierarchical cosmological models slightly reduce the above limits., J.M. acknowledge support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, grant agreement number 772293). A.M.S. is partially supported by the Spanish Government (ESP2017-82674-R) and Generalitat de Catalunya (2017-SGR-1131). T.L.C. acknowledges support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 792848 (PULSATION). K.J.B., S.H., J.S.K. and N.T. are supported by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 338251 (StellarAges). E.C. is funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement number 664931. L.G.-C. acknowledges support from the MINECO FPI-SO doctoral research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610. S.M. acknowledges support from the Spanish ministry through the Ramon y Cajal fellowship number RYC-2015-17697. This work was supported by FEDER through COMPETE2020 (POCI-01-0145-FEDER-030389. A.M.B. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 749962 (project THOT).
- Published
- 2020
41. Using AI to detect panic buying and improve products distribution amid pandemic.
- Author
-
Adulyasak Y, Benomar O, Chaouachi A, Cohen MC, and Khern-Am-Nuai W
- Abstract
The COVID-19 pandemic has triggered panic-buying behavior around the globe. As a result, many essential supplies were consistently out-of-stock at common point-of-sale locations. Even though most retailers were aware of this problem, they were caught off guard and are still lacking the technical capabilities to address this issue. The primary objective of this paper is to develop a framework that can systematically alleviate this issue by leveraging AI models and techniques. We exploit both internal and external data sources and show that using external data enhances the predictability and interpretability of our model. Our data-driven framework can help retailers detect demand anomalies as they occur, allowing them to react strategically. We collaborate with a large retailer and apply our models to three categories of products using a dataset with more than 15 million observations. We first show that our proposed anomaly detection model can successfully detect anomalies related to panic buying. We then present a prescriptive analytics simulation tool that can help retailers improve essential product distribution in uncertain times. Using data from the March 2020 panic-buying wave, we show that our prescriptive tool can help retailers increase access to essential products by 56.74%., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2023, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)
- Published
- 2023
- Full Text
- View/download PDF
42. Shape of a slowly rotating star measured by asteroseismology.
- Author
-
Gizon L, Sekii T, Takata M, Kurtz DW, Shibahashi H, Bazot M, Benomar O, Birch AC, and Sreenivasan KR
- Abstract
Stars are not perfectly spherically symmetric. They are deformed by rotation and magnetic fields. Until now, the study of stellar shapes has only been possible with optical interferometry for a few of the fastest-rotating nearby stars. We report an asteroseismic measurement, with much better precision than interferometry, of the asphericity of an A-type star with a rotation period of 100 days. Using the fact that different modes of oscillation probe different stellar latitudes, we infer a tiny but significant flattening of the star's shape of Δ R / R = (1.8 ± 0.6) × 10
-6 . For a stellar radius R that is 2.24 times the solar radius, the difference in radius between the equator and the poles is Δ R = 3 ± 1 km. Because the observed Δ R / R is only one-third of the expected rotational oblateness, we conjecture the presence of a weak magnetic field on a star that does not have an extended convective envelope. This calls to question the origin of the magnetic field.- Published
- 2016
- Full Text
- View/download PDF
43. Seismic constraints on rotation of Sun-like star and mass of exoplanet.
- Author
-
Gizon L, Ballot J, Michel E, Stahn T, Vauclair G, Bruntt H, Quirion PO, Benomar O, Vauclair S, Appourchaux T, Auvergne M, Baglin A, Barban C, Baudin F, Bazot M, Campante T, Catala C, Chaplin W, Creevey O, Deheuvels S, Dolez N, Elsworth Y, García R, Gaulme P, Mathis S, Mathur S, Mosser B, Régulo C, Roxburgh I, Salabert D, Samadi R, Sato K, Verner G, Hanasoge S, and Sreenivasan KR
- Subjects
- Astronomy, Models, Theoretical, Planets, Rotation, Stars, Celestial
- Abstract
Rotation is thought to drive cyclic magnetic activity in the Sun and Sun-like stars. Stellar dynamos, however, are poorly understood owing to the scarcity of observations of rotation and magnetic fields in stars. Here, inferences are drawn on the internal rotation of a distant Sun-like star by studying its global modes of oscillation. We report asteroseismic constraints imposed on the rotation rate and the inclination of the spin axis of the Sun-like star HD 52265, a principal target observed by the CoRoT satellite that is known to host a planetary companion. These seismic inferences are remarkably consistent with an independent spectroscopic observation (rotational line broadening) and with the observed rotation period of star spots. Furthermore, asteroseismology constrains the mass of exoplanet HD 52265b. Under the standard assumption that the stellar spin axis and the axis of the planetary orbit coincide, the minimum spectroscopic mass of the planet can be converted into a true mass of 1.85(-0.42)(+0.52)M(Jupiter), which implies that it is a planet, not a brown dwarf.
- Published
- 2013
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.