8 results on '"Baudin, F"'
Search Results
2. Modeling of two CoRoT solar analogues constrained by seismic and spectroscopic analysis.
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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
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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
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3. Differential asteroseismic study of seismic twins observed by CoRoT
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Ozel, N., Mosser, B., Dupret, M. A., Bruntt, H., Barban, C., Deheuvels, S., García, R. A., Michel, E., Samadi, R., Baudin, F., Mathur, S., Régulo, C., Auvergne, M., Catala, C., Morel, Pierre, Pichon, B., 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), 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), 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, and PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)
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techniques: photometric ,Astrophysics::Solar and Stellar Astrophysics ,stars: individual: HD 181420 ,Astrophysics::Earth and Planetary Astrophysics ,stars: evolution ,asteroseismology ,stars: interiors ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,stars: individual: HD 175272 - Abstract
International audience; Context. The CoRoT short asteroseismic runs give us the opportunity to observe a large variety of late-type stars through their solar-like oscillations. We report the observation and modeling of the F5V star HD 175272.Aims. Our aim is to define a method for extracting as much information as possible from a noisy oscillation spectrum. Methods. We followed a differential approach that consists of using a well-known star as a reference to characterize another star. We used classical tools such as the envelope autocorrelation function to derive the global seismic parameters of the star. We compared HD 175272 with HD 181420 through a linear approach, because they appear to be asteroseismic twins.Results. The comparison with the reference star enables us to substantially enhance the scientific output for HD 175272. First, we determined its global characteristics through a detailed seismic analysis of HD 181420. Second, with our differential approach, we measured the difference of mass, radius and age between HD 175272 and HD 181420.Conclusions. We have developed a general method able to derive asteroseismic constraints on a star even in case of low-quality data. This method can be applied to stars with interesting properties but low signal-to-noise ratio oscillation spectrum, such as stars hosting an exoplanet or members of a binary system.
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- 2013
4. Amplitude and lifetime of radial modes in red giant star spectra observed by Kepler.
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Vrard, M., Kallinger, T., Mosser, B., Barban, C., Baudin, F., Belkacem, K., and Cunha, M. S.
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STELLAR evolution ,RED giant spectra ,ASTRONOMICAL photometry ,ASTEROSEISMOLOGY ,NATURAL satellites ,SOLAR oscillations - Abstract
Context. The space-borne missions CoRoT and Kepler have provided photometric observations of unprecedented quality. The study of solar-like oscillations observed in red giant stars by these satellites allows a better understanding of the different physical processes occurring in their interiors. In particular, the study of the mode excitation and damping is a promising way to improve our understanding of stellar physics that has, so far, been performed only on a limited number of targets. Aims. The recent asteroseismic characterization of the evolutionary status for a large number of red giants allows us to study the physical processes acting in the interior of red giants and how they are modified during stellar evolution. In this work, we aim to obtain information on the excitation and damping of pressure modes through the measurement of the stars' pressure mode widths and amplitudes and to analyze how they are modified with stellar evolution. The objective is to bring observational constraints on the modeling of the physical processes behind mode excitation and damping. Methods. We fit the frequency spectra of red giants with well-defined evolutionary status using Lorentzian functions to derive the pressure mode widths and amplitudes. To strengthen our conclusions, we used two different fitting techniques. Results. Pressure mode widths and amplitudes were determined for more than 5000 red giants. With a stellar sample two orders of magnitude larger than previous results, we confirmed that the mode width depends on stellar evolution and varies with stellar effective temperature. In addition, we discovered that the mode width depends on stellar mass. We also confirmed observationally the influence of the stellar metallicity on the mode amplitudes, as predicted by models. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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5. The tip of the iceberg: the frequency content of the δ Sct star HD 50844 from CoRoT space photometry.
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Poretti, E., Mantegazza, L., Rainer, M., Uytterhoeven, K., Michel, E., Baglin, A., Auvergne, M., Catala, C., Samadi, R., Rodríguez, E., Garrido, R., Amado, P., Martín-Ruiz, S., Moya, A., Suárez, J. C., Baudin, F., Zima, W., Alvarez, M., Mathias, P., and Paparó, M.
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VARIABLE stars ,PULSATING stars ,STELLAR collisions ,ASTRONOMICAL photometry ,ASTRONOMICAL spectroscopy ,STAR observations - Abstract
It has been suggested that the detection of a wealth of very low amplitude modes in δ Sct stars was only a matter of signal-to-noise ratio. Access to this treasure, impossible from the ground, is one of the scientific aims of the space mission CoRoT, developed and operated by CNES. This work presents the results obtained on HD 50844: the 140,016 datapoints allowed us to reach the level of 10
-5 mag in the amplitude spectra. The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0–30 d-1 . The initial guess that δ Sct stars have a very rich frequency content is confirmed. The spectroscopic mode identification gives theoretical support since very high-degree modes (up to l = 14) are identified. We also prove that cancellation effects are not sufficient in removing the flux variations associated to these modes at the noise level of the CoRoT measurements. The ground-based observations indicate that HD 50844 is an evolved star that is slightly underabundant in heavy elements, located on the Terminal Age Main Sequence. The predominant term (f1 = 6.92 d-1 ) has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data. [ABSTRACT FROM AUTHOR]- Published
- 2009
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6. An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy Large separation as a new observable for δ Scuti stars.
- Author
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García Hernández, A., Moya, A., Michel, E., Suárez, J. C., Poretti, E., Martín-Ruíz, S., Amado, P. J., Garrido, R., Rodríguez, E., Rainer, M., Uytterhoeven, K., Rodrigo, C., Solano, E., Rodón, J. R., Mathias, P., Rolland, A., Auvergne, M., Baglin, A., Baudin, F., and Catala, C.
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STARS ,ASTRONOMICAL photometry ,ASTRONOMICAL spectroscopy ,FREQUENCY spectra ,PHYSICAL cosmology ,MATHEMATICAL models - Abstract
Aims. The aim of this work was to use a multi-approach technique to derive the most accurate values possible of the physical parameters of the δ Sct star HD174966, which was observed with the CoRoT satellite. In addition, we searched for a periodic pattern in the frequency spectra with the goal of using it to determine the mean density of the star. Methods. First, we extracted the frequency content from the CoRoT light curve. Then, we derived the physical parameters of HD174966 and carried a mode identification out from the spectroscopic and photometric observations. We used this information to look for the models fulfilling all the conditions and discussed the inaccuracies of the method because of the rotation effects. In a final step, we searched for patterns in the frequency set using a Fourier transform, discussed its origin, and studied the possibility of using the periodicity to obtain information about the physical parameters of the star. Results. A total of 185 peaks were obtained from the Fourier analysis of the CoRoT light curve, all of which were reliable pulsating frequencies. From the spectroscopic observations, 18 oscillation modes were detected and identified, and the inclination angle (62.5°
+7.5 -17.5 ) were estimated. From the multi-colour photometric observations, only three frequencies were detected that correspond to the main ones in the CoRoT light curve. We looked for periodicities within the 185 frequencies and found a quasiperiodic pattern ▵ v ~ 64 μHz. Using the inclination angle, the rotational velocity, and an Echelle diagram (showing a double comb outside the asymptotic regime), we concluded that the periodicity corresponds to a large separation structure. The quasiperiodic pattern allowed us to discriminate models from a grid. As a result, the value of the mean density is achieved with a 6% uncertainty. So, the ▵ v pattern could be used as a new observable for A-F type stars. [ABSTRACT FROM AUTHOR]-1 ) were estimated. From the multi-colour photometric observations, only three frequencies were detected that correspond to the main ones in the CoRoT light curve. We looked for periodicities within the 185 frequencies and found a quasiperiodic pattern ▵ v ~ 64 μHz. Using the inclination angle, the rotational velocity, and an Echelle diagram (showing a double comb outside the asymptotic regime), we concluded that the periodicity corresponds to a large separation structure. The quasiperiodic pattern allowed us to discriminate models from a grid. As a result, the value of the mean density is achieved with a 6% uncertainty. So, the ▵ v pattern could be used as a new observable for A-F type stars. [ABSTRACT FROM AUTHOR]- Published
- 2013
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7. Pulsation spectrum of δ Scuti stars: the binary HD 50870 as seen with CoRoT and HARPS.
- Author
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Mantegazza, L., Poretti, E., Michel, E., Rainer, M., Baudin, F., García Hernández, A., Semaan, T., Alvarez, M., Amado, P. J., Garrido, R., Mathias, P., Moya, A., Suárez, J. C., Auvergne, M., Baglin, A., Catala, C., and Samadi, R.
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STELLAR oscillations ,ASTRONOMICAL observations ,HIGH resolution spectroscopy ,PHOTOMETRY ,ASTROPHYSICS - Abstract
Aims. We present the results obtained with the CoRoT satellite for HD 50870, a δ Sct star which was observed for 114.4 d. The aim of these observations was to evaluate the results obtained for HD 50844, the first S Sct star monitored with CoRoT, on a longer time baseline. Methods. The 307,570 CoRoT datapoints were analysed with different techniques. The photometric observations were complemented over 15 nights of high-resolution spectroscopy with HARPS on a baseline of 25 d. These spectra were analysed to study the line profile variations and to derive the stellar physical parameters. Some uvby photometric observations were also obtained to better characterize the pulsation modes. Results. HD 50870 proved to be a low-amplitude, long-period spectroscopic binary system seen almost pole-on (i ≃ 21°). The brighter component, which also has the higher rotational velocity (v sin i = 37.5 km s
-1 ), is a δ Sct-type variable with a full light amplitude variation of about 0.04 mag. There is a dominant axisymmetric mode (17.16 d-1 ). Moreover, there are two groups of frequencies (about 19) in the intervals 6-9 and 13-18 d-1 , with amplitudes ranging from a few mmag to 0.3 mmag. After the detection of about 250 terms (corresponding to an amplitude of about 0.045 mmag) a flat plateau appears in the power spectrum in the low-frequency region up to about 35 d-1 We were able to detect this plateau only thanks to the short cadence sampling of the CoRoT measurements (32 s). The density distribution vs. frequency of the detected frequencies seems to rule out the possibility that this plateau is the result of a process with a continuum power spectrum. The spacings of the strongest modes suggest a quasi-periodic pattern. We failed to find a satisfactory seismic model that simultaneously matches the frequency range, the position in the HR diagram, and the quasi-periodic pattern interpreted as a large separation. Nineteen modes were detected spectroscopically from the line profile variations and associated to the photometric ones. Tentative l, m values have been attributed to the modes detected spectroscopically. Prograde as well as retrograde modes are present with C values up to 9. There are no traces of variability induced by solar-like oscillations. [ABSTRACT FROM AUTHOR]- Published
- 2012
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8. Modelling a high-mass red giant observed by CoRoT.
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Baudin, F., Barban, C., Goupil, M. J., Samadi, R., Lebreton, Y., Bruntt, H., Morel, T., Lefèvre, L., Michel, E., Mosser, B., Carrier, F., De Ridder, J., Hatzes, A., Hekker, S., Kallinger, T., Auvergne, M., Baglin, A., and Catala, C.
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RED giants , *PHOTOMETERS , *NOBLE gases , *RADIOACTIVITY , *ASTROPHYSICS - Abstract
Context. The advent of space-borne photometers such as CoRoT and Kepler has opened up new fields in asteroseismology. This is especially true for red giants as only a few of these stars were known to oscillate with small amplitude, solar-like oscillations before the launch of CoRoT. Aims. The G6 giant HR2582 (HD50890) was observed by CoRoT for approximately 55 days. We present here the analysis of its light curve and the characterisation of the star using different observables, such as its location in the Hertzsprung-Russell diagram and seismic observables. Methods. Mode frequencies are extracted from the observed Fourier spectrum of the light curve. Numerical stellar models are then computed to determine the characteristics of the star (mass, age, etc.) from the comparison with observational constraints. Results. We provide evidence for the presence of solar-like oscillations at low frequency, between 10 and 20 μHz, with a regular spacing of (1.7±0.1) μHz between consecutive radial orders. Only radial modes are clearly visible. From the models compatible with the observational constraints used here,We find that HR2582 (HD50890) is a massive star with a mass in the range (3-5 M☉), clearly above the red clump. It oscillates with rather low radial order (n = 5-12) modes. Its evolutionary stage cannot be determined with precision: the star could be on the ascending red giant branch (hydrogen shell burning) with an age of approximately 155 Myr or in a later phase (helium burning). In order to obtain a reasonable helium amount, the metallicity of the star must be quite subsolar. Our best models are obtained with a mixing length significantly smaller than that obtained for the Sun with the same physical description (except overshoot). The amount of core overshoot during the main-sequence phase is found to be mild, of the order of 0.1 Hp. Conclusions. HR 2582 (HD50890) is an interesting case as only a few massive stars can be observed due to their rapid evolution compared to less massive red giants. HR2582 (HD50890) is also one of the few cases that can be used to validate the scaling relations for massive red giants stars and its sensitivity to the physics of the star. [ABSTRACT FROM AUTHOR]
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- 2012
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