References of "Suarez, J. C"
     in
Bookmark and Share    
See detailRotation Effects as Possible Responsible for the Surface Effects on the Sun and Solar-Type Stars
Suárez, J. C.; Goupil, M. J.; Reese, Daniel ULg et al

in Suárez, Juan Carlos; Garrido, Rafael; Balona, Luis A. (Eds.) et al Stellar Pulsations (2013)

One of the main sources of uncertainty in the asteroseismic models of the Sun and solar-like stars is the poor match between predicted oscillation frequencies and observed ones in the very high frequency ... [more ▼]

One of the main sources of uncertainty in the asteroseismic models of the Sun and solar-like stars is the poor match between predicted oscillation frequencies and observed ones in the very high frequency domain. Today, effects of turbulence, diffusion, etc., i.e., the so-called "surface effects" are signaled as possible responsible for such a discrepancy. We show that the effect of the stellar deformation due to rotation is of the same order or even larger than these effects. We show that rotation effects, are important for the asteroseismic analysis of the Sun and solar-like stars and they cannot be neglected when modeling such stars. [less ▲]

Detailed reference viewed: 16 (2 ULg)
See detailRotation on the oscillation spectrum of solar-like stars
Suárez, J. C.; Goupil, M.-J.; Reese, Daniel ULg et al

in Alecian, G.; Belkacem, K.; Samadi, R. (Eds.) et al SF2A-2011: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics (2011, December 01)

One of the main sources of uncertainty in the asteroseismic models of solar-like stars is the poor match between predicted oscillation frequencies and observed ones in the very high frequency domain ... [more ▼]

One of the main sources of uncertainty in the asteroseismic models of solar-like stars is the poor match between predicted oscillation frequencies and observed ones in the very high frequency domain. Today, such deviation is usually corrected by fitting the affected frequencies with polynomials which are then physically explained by possible effects of turbulence, diffusion, etc., i.e., the so-called ``surface effects". In this work, we show that the effect of the stellar deformation due to rotation is of the same order or even larger than the aforementioned surface effects. Moreover, we show that rotation effects, even for the low velocities generally observed in solar-like stars, becomes important for the asteroseismic analysis and cannot be neglected when modeling such stars. [less ▲]

Detailed reference viewed: 14 (1 ULg)
Full Text
Peer Reviewed
See detailKepler observations of the variability in B-type stars
Balona, L. A.; Pigulski, A.; Cat, P De et al

in Monthly Notices of the Royal Astronomical Society (2011), 413

The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies, characteristic of slowly pulsating B (SPB) stars ... [more ▼]

The analysis of the light curves of 48 B-type stars observed by Kepler is presented. Among these are 15 pulsating stars, all of which show low frequencies, characteristic of slowly pulsating B (SPB) stars. Seven of these stars also show a few weak, isolated high frequencies and they could be considered as SPB/β Cephei (β Cep) hybrids. In all cases, the frequency spectra are quite different from what is seen from ground-based observations. We suggest that this is because most of the low frequencies are modes of high degree which are predicted to be unstable in models of mid-B stars. We find that there are non-pulsating stars within the β Cep and SPB instability strips. Apart from the pulsating stars, we can identify stars with frequency groupings similar to what is seen in Be stars but which are not Be stars. The origin of the groupings is not clear, but may be related to rotation. We find periodic variations in other stars which we attribute to proximity effects in binary systems or possibly rotational modulation. We find no evidence for pulsating stars between the cool edge of the SPB and the hot edge of the δ Sct instability strips. None of the stars shows the broad features which can be attributed to stochastically excited modes as recently proposed. Among our sample of B stars are two chemically peculiar stars, one of which is a HgMn star showing rotational modulation in the light curve. [less ▲]

Detailed reference viewed: 22 (10 ULg)
Full Text
Peer Reviewed
See detailThe Asteroseismic Potential of Kepler: First Results for Solar-Type Stars
Chaplin, W. J.; Appourchaux, T.; Elsworth, Y. et al

in Astrophysical Journal Letters (2010), 713

We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise ... [more ▼]

We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: about 20 modes of oscillation may be clearly distinguished in each star. We discuss the appearance of the oscillation spectra, use the frequencies and frequency separations to provide first results on the radii, masses, and ages of the stars, and comment in the light of these results on prospects for inference on other solar-type stars that Kepler will observe. [less ▲]

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailGround-based observations of the beta Cephei CoRoT main target HD 180 642: abundance analysis and mode identification
Briquet, Maryline ULg; Uytterhoeven, K.; Morel, Thierry ULg et al

in Astronomy and Astrophysics (2009), 506

The known β Cephei star HD 180 642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for the first time (Degroote ... [more ▼]

The known β Cephei star HD 180 642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for the first time (Degroote and collaborators). In this paper, we obtain additional constraints for forthcoming asteroseismic modeling of the target. Our results are based on both extensive ground-based multicolour photometry and high-resolution spectroscopy. We determine T_eff = 24 500± 1000 K and log g = 3.45± 0.15 dex from spectroscopy. The derived chemical abundances are consistent with those for B stars in the solar neighbourhood, except for a mild nitrogen excess. A metallicity Z = 0.0099± 0.0016 is obtained. Three modes are detected in photometry. The degree â is unambiguously identified for two of them: â = 0 and â = 3 for the frequencies 5.48694 d[SUP]-1[/SUP] and 0.30818 d[SUP]-1[/SUP], respectively. The radial mode is non-linear and highly dominant with an amplitude in the U-filter about 15 times larger than the strongest of the other modes. For the third frequency of 7.36673 d[SUP]-1[/SUP] found in photometry, two possibilities remain: â = 0 or 3. In the radial velocities, the dominant radial mode presents a so-called stillstand but no clear evidence of the existence of shocks is observed. Four low-amplitude modes are found in spectroscopy and one of them, with frequency 8.4079 d[SUP]-1[/SUP], is identified as (â ,m)=(3,2). Based on this mode identification, we finally deduce an equatorial rotational velocity of 38± 15 km s[SUP]-1[/SUP]. Based on data gathered with the 1.2m Mercator telescope Roque de los Muchachos, La Palma, the 90cm telescope at Sierra Nevada Observatory, Spain, the 1.5 m telescope at San Pedro Mártir Observatory, Mexico, the 1m RCC and 50 cm telescope at the PiszkéstetÅ Mountain Station of Konkoly Observatory, Hungary, the 2.2 m ESO telescope (ESO Programme 077.D-0311; ESO Large Programme 178.D-0361) at La Silla, Chile, the 1.93 m and 1.52 m telescopes at the Haute-Provence Observatory, France. Current address: Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, centre de Saclay, 91191 Gif-sur-Yvette, France. [less ▲]

Detailed reference viewed: 26 (6 ULg)
See detailAn asteroseismic study of the beta Cephei CoRoT main target HD 180642: results from the ground-based campaign
Briquet, Maryline ULg; Uytterhoeven, K.; Morel, Thierry ULg et al

in American Institute of Physics Conference Series (2009, September 01)

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009 ... [more ▼]

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009). In the present study, we provide additional information on the target, based on both ground-based multi-colour photometry and high-resolution spectroscopy. We place our object in the (T[SUB]eff[/SUB], log g) diagram. In addition, we derive the chemical abundances of several elements as well as the metallicity of HD 180642. Finally, we put constraints on the identification of some modes. All these observational constraints will be used to compute stellar models of the target. [less ▲]

Detailed reference viewed: 26 (6 ULg)
Full Text
Peer Reviewed
See detailGround-based observations of the beta Cephei CoRoT main target HD 180642
Briquet, Maryline ULg; Uytterhoeven, K.; Aerts, C. et al

in Communications in Asteroseismology (2009), 158

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD~180642. Besides the non-linear dominant ... [more ▼]

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD~180642. Besides the non-linear dominant radial mode several low-amplitude modes are detected in both kinds of datasets. Our aim is to derive the wavenumbers (â ,m) of these modes, as additional constraints to the CoRoT pulsation frequencies, for forthcoming asteroseismic modelling of the star. [less ▲]

Detailed reference viewed: 15 (3 ULg)
Full Text
Peer Reviewed
See detailGround-based observations of the beta Cephei CoRoT main target HD 180642
Briquet, Maryline ULg; Uytterhoeven, K.; Aerts, C. et al

Conference (2008, July)

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant ... [more ▼]

We present the preliminary results of a detailed study of ground-based photometric and spectroscopic observations dedicated to the β Cephei CoRoT main target HD 180642. Besides the non-linear dominant radial mode several low-amplitude modes are detected in both kinds of datasets. Our aim is to derive the wavenumbers (ℓ,m) of these modes, as additional constraints to the CoRoT pulsation frequencies, for forthcoming asteroseismic modelling of the star. [less ▲]

Detailed reference viewed: 13 (3 ULg)
Full Text
Peer Reviewed
See detailA procedure for modelling asymptotic g-mode pulsators: The case of gamma Doradus stars
Moya, A.; Suárez, J. C.; Martín-Ruiz, S. et al

in Astronomische Nachrichten (2008), 329

Mode identification is one of the first and main problems we encounter in trying to develop the complete potential of asteroseismology. In the particular case of {g}-mode pulsators, this is still an ... [more ▼]

Mode identification is one of the first and main problems we encounter in trying to develop the complete potential of asteroseismology. In the particular case of {g}-mode pulsators, this is still an unsolved problem, from both the observational and theoretical points of view. Nevertheless, in recent years, some observational and theoretical efforts have been made to find a solution. In this work we use the latest theoretical and computational tools to understand asymptotic {g}-mode pulsators: 1) the Frequency Ratio Method, and 2) Time Dependent Convection. With these tools, a self-consistent procedure for mode identification and modelling of these {g}-mode pulsators can be constructed. This procedure is illustrated using observational information available for the gamma Doradus star 9 Aurigae. [less ▲]

Detailed reference viewed: 12 (2 ULg)
Full Text
Peer Reviewed
See detailThe field high-amplitude SX Phoenicis variable BL Camelopardalis: results from a multisite photometric campaign. I. Pulsation
Rodríguez, E.; Fauvaud, S.; Farrell, J. A. et al

in Astronomy and Astrophysics (2007), 471

Context: BL Cam is an extreme metal-deficient field high-amplitude SX Phe-type variable where a very complex frequency spectrum is detected, with a number of independent nonradial modes excited, unusual ... [more ▼]

Context: BL Cam is an extreme metal-deficient field high-amplitude SX Phe-type variable where a very complex frequency spectrum is detected, with a number of independent nonradial modes excited, unusual among the high-amplitude pulsators in the Lower Classical Instability Strip. Aims: An extensive and detailed study has been carried out to investigate the pulsational content and properties of this object. Methods: The analysis is based on 283 h of CCD observations obtained in the Johnson V filter, during a long multisite photometric campaign carried out along the Northern autumn-winter of 2005-2006. Additionally, multicolour BI photometry was also collected to study the phase shifts and amplitude ratios, between light curves obtained in different filters, for modal discrimination of the main excited modes. Results: The detailed frequency analysis revealed a very rich and dense pulsational content consisting of 25 significant peaks, 22 of them corresponding to independent modes: one is the already known main periodicity f[SUB]0[/SUB] = 25.5765 cd[SUP]-1[/SUP] (Delta V = 153 mmag) and the other 21 are excited modes showing very small amplitudes. Some additional periodicities are probably still remaining in the residuals. This represents the most complex spectrum ever detected in a high-amplitude pulsator of this type. The majority of the secondary modes suspected from earlier works are confirmed here and, additionally, a large number of new peaks are detected. The amplitude of the main periodicity f[SUB]0[/SUB] seems to be stable during decades, but the majority of the secondary modes show strong amplitude changes from one epoch to another. The suspected fundamental radial nature of the main periodicity of BL Cam is confirmed, while the secondary peak f[SUB]1[/SUB] = 25.2523 cd[SUP]-1[/SUP] is identified as a nonradial mixed mode g[SUB]4[/SUB] with l = 1. The radial double-mode nature, claimed by some authors for the main two frequencies of BL Cam, is not confirmed. Nevertheless, the frequency f[SUB]6[/SUB] = 32.6464 cd[SUP]-1[/SUP] could correspond to the first radial overtone. [less ▲]

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
See detailAn asteroseismic Main Sequence model for the delta Scuti star 44 Tau
Garrido, R.; Suárez, J. C.; Grigahcène, A. et al

in Communications in Asteroseismology (2007), 150

Not Available

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detaillambda Boo stars among the gamma Dor-type pulsators: the cases of HD 218427 and HD 239276
Rodríguez, E.; Suárez, J. C.; Moya, A. et al

in Communications in Asteroseismology (2007), 150

Not Available

Detailed reference viewed: 7 (1 ULg)
Full Text
See detailThe Seismology Programme of CoRoT
Michel, Eric; Baglin, A.; Auvergne, M. et al

in Proceedings of "The CoRoT Mission Pre-Launch Status - Stellar Seismology and Planet Finding (2006, November 01)

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working ... [more ▼]

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working Group. With a few illustrative examples, we show how CoRoT data will help to address various problems associated with present open questions of stellar structure and evolution. [less ▲]

Detailed reference viewed: 52 (34 ULg)
Full Text
See detailWhy Bothering to Measure Stellar Rotation with CoRoT?
Goupil, Marie-José; Moya, A.; Suarez, J. C. et al

in ESA Special Publication (2006, November 01)

One important goal of the CoRoT experiment is to obtain information about the internal rotation of stars, in particular the ratio of central to surface rotation rates. This will provide constraints on the ... [more ▼]

One important goal of the CoRoT experiment is to obtain information about the internal rotation of stars, in particular the ratio of central to surface rotation rates. This will provide constraints on the modelling of transport mechanisms of angular momentum acting in radiative (rotationally induced turbulent) and convective zones (plumes, extension beyond convectively instable regions). Relations between the surface rotation period and age, magnetic activity, mass loss and other stellar characteristics can also be studied with a statistically significant set of data as will be provided by Corot. We present various theoretical efforts performed over the past years in order to develope the theoretical tools which will enable us to study rotation with Corot. [less ▲]

Detailed reference viewed: 15 (1 ULg)
Full Text
Peer Reviewed
See detailAsteroseismology of the new multiperiodic gamma Dor variable HD 239276
Rodríguez, E.; Costa, V.; Zhou, A*-Y et al

in Astronomy and Astrophysics (2006), 456

The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain ... [more ▼]

The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain, in uvbybeta Strömgren-Crawford photometry, and China, using the Johnson V filter. Two low-dispersion spectra were also collected. The results establish this star as a new multiperiodic gamma Dor-type pulsator with deficiency in metallicity. Its possible lambda Boo nature is discussed. The frequency analysis shows three pulsational frequencies as significant, but some more are probably present among the residuals. The method based on phase shifts and amplitude ratios in multicolour photometry is used to identify the excited modes with non-adiabatic time-dependent convection models. A very good agreement between the theoretical and observed amplitude ratios is obtained and the two main modes are identified as l=1 modes. Nevertheless, our results do not allow us to discriminate between a solar abundance and a metal deficient nature for this star. The frequency ratio method is further used for the identification of the modes. The results suggest low metallicity for this star, but a lambda Boo nature may be not ruled out. [less ▲]

Detailed reference viewed: 3 (0 ULg)
Full Text
Peer Reviewed
See detailThe frequency ratio method and the new multiperiodic gamma Doradus star HD 218427
Rodríguez, E.; Amado, P. J.; Suárez, J. C. et al

in Astronomy and Astrophysics (2006), 450

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected ... [more ▼]

Oscillations of gamma Dor-type were discovered in the star HD 218427 through simultaneous uvby photometric observations carried out in the year 2003. A few Hbeta-Crawford measurements were also collected for calibration purposes and they locate this star well inside the gamma Dor instability region. We find HD 218427 to be deficient in metals, similar to other well-defined gamma Dor stars, and discuss the possibility that it has a lambda Boo nature. We carried out frequency analysis for different filters, including the combined "vby" filter, and five frequencies were found as significant with periods ranging between 0.3 and 0.8 days. The recently-developed frequency ratio method is used in order to identify the excited modes. The results are consistent with an l=2 identification for all the modes and with high radial quantum numbers (nË 40) for the three main observed periodicities. The possibility of multiplet structures is also discussed. However, no consistency is found when using the time-dependent convection treatment to discriminate modes. This disagreement can be due to the large rotation velocity taking place in HD 218427 and, consequently, the significant coupling between the modes. [less ▲]

Detailed reference viewed: 6 (0 ULg)
Full Text
See detailFirst unambiguous asteroseismologic modelling of a gamma Doradus star
Moya, A.; Grigahcene, A.; Suárez, J. C. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard ... [more ▼]

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard photometric observations (at least three oscillation frequencies, a photometric error box in the HR diagram and multicolor photometric observations, in this case in the Strömgren system) we can reduce the possible theoretical models for this star, providing constraints to the stellar parameters as mass, overshooting, metallicity, MLT parameter alpha , Brunt-Väiälä integral (I[SUB]th[/SUB]), etc. Simultaneously, an estimate of the modal identification of the observed frequencies is also obtained. This can be possible by the application, for the first time, of a complete procedure where different theoretical and computational techniques, recently developed, are linked and compared with photometric observations. The Frequency Ratio Method (FRM) and the Time Dependent Convection (TDC) theory are the basis of this complete procedure. [less ▲]

Detailed reference viewed: 7 (2 ULg)
Full Text
See detailNon-adiabatic seismic study of the triple system DG Leo
Grigahcène, A.; Suárez, J. C.; Dupret, Marc-Antoine ULg et al

in Tidal Evolution and Oscillations in Binary Stars (2005, November 01)

The interest in studying multiple systems comes from the fact that they give a good number of constraints on their components. From the multiplicity we have constraints on mass and age. Moreover, if one ... [more ▼]

The interest in studying multiple systems comes from the fact that they give a good number of constraints on their components. From the multiplicity we have constraints on mass and age. Moreover, if one or more components of the system show oscillating properties as the DG Leo triple system, additional constraints provided by seismology can be obtained once the modes are identified. In this work, we consider an equilibrium model of the DG Leo system constrained by its multiplicity properties, we attempt to check our new Time Depending Convection treatment on the modes identification of the DG Leo system. [less ▲]

Detailed reference viewed: 3 (0 ULg)
Full Text
Peer Reviewed
See detailAsteroseismology of delta Scuti Stars: Problems and Prospects
Goupil, Marie-José; Dupret, Marc-Antoine ULg; Samadi, R. et al

in Journal of Astrophysics & Astronomy (2005), 26

We briefly outline the state-of-the-art seismology of delta Scuti stars from a theoretical point of view: why is it so difficult a task? The recent theoretical advances in the field that these ... [more ▼]

We briefly outline the state-of-the-art seismology of delta Scuti stars from a theoretical point of view: why is it so difficult a task? The recent theoretical advances in the field that these difficulties have influenced are also discussed. [less ▲]

Detailed reference viewed: 14 (2 ULg)