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See detailAsteroseismology of HD 129929: Core Overshooting and Nonrigid Rotation
Aerts, C.; Thoul, Anne ULg; Daszynska, J. et al

in Science (2003), 300

We have gathered and analyzed 1493 high-quality multicolor Geneva photometric data taken over 21 years of the B3V star HD 129929. We detect six frequencies, among which appear the effects of rotational ... [more ▼]

We have gathered and analyzed 1493 high-quality multicolor Geneva photometric data taken over 21 years of the B3V star HD 129929. We detect six frequencies, among which appear the effects of rotational splitting with a spacing of ~0.0121 cycles per day, which implies that the star rotates very slowly. A nonadiabatic analysis of the oscillations allows us to constrain the metallicity of the star to Z â [0.017,0.022], which agrees with a similar range derived from spectroscopic data. We provide evidence for the occurrence of core convective overshooting in the star, with alpha[SUB]ov[/SUB] = 0.10 +/- 0.05, and we rule out rigid rotation. [less ▲]

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See detailAsteroseismology of hot B subdwarf stars
Charpinet, Stéphane; Van Grootel, Valérie ULg; Brassard, Pierre et al

in EPJ Web of Conferences (2013, March), 43

Nonradial pulsations in Extreme Horizontal Branch stars (also known as hot B subdwarfs or sdB stars) offer strong opportunities to study through asteroseismology the structure and internal dynamics of ... [more ▼]

Nonradial pulsations in Extreme Horizontal Branch stars (also known as hot B subdwarfs or sdB stars) offer strong opportunities to study through asteroseismology the structure and internal dynamics of stars in this intermediate stage of stellar evolution. Most sdB stars directly descend from former red giants and are expected to evolve straight into white dwarfs after core helium exhaustion. They thus represent the most direct link between these two stages. Their properties should therefore reflect both the outcome of the core evolution of red giant stars and the initial state for a fraction of the white dwarfs. We review the status of this field after a decade of efforts to exploit both p-mode and g-mode pulsating sdB stars as asteroseismic laboratories. From the discoveries of these two classes of pulsators in 1997 and 2003, respectively, up to the current epoch of data gathering of unprecedented quality from space, a lot of progress has been made in this area and prospects for future achievements look very promising. [less ▲]

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See detailAsteroseismology of OB stars with CoRoT
Degroote, P.; Aerts, C.; Samadi, R. et al

in Astronomische Nachrichten (2010), 331

The CoRoT satellite is revolutionizing the photometric study of massive O-type and B-type stars. During its long runs, CoRoT observed the entire main sequence B star domain, from typical hot β Cep stars ... [more ▼]

The CoRoT satellite is revolutionizing the photometric study of massive O-type and B-type stars. During its long runs, CoRoT observed the entire main sequence B star domain, from typical hot β Cep stars, via cooler hybrid p- and g-mode pulsators to the SPB stars near the edge of the instability strip. CoRoT lowers the sensitivity barrier from the typical mmag-precision reached from the ground, to the μmag-level reached from space. Within the wealth of detected and identified pulsation modes, relations have been found in the form of multiplets, combination of frequencies, and frequency- and period spacings. This wealth of observational evidence is finally providing strong constraints to test current models of the internal structure and pulsations of hot stars. Aside from the expected opacity driven modes with infinite lifetime, other unexpected types of variability are detected in massive stars, such as modes of stochastic nature. The simultaneous observation of all these light curve characteristics implies a challenge for both observational asteroseismology and stellar modelling. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. [less ▲]

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See detailAsteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819
Miglio, A.; Brogaard, K.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K ... [more ▼]

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by combining the available seismic parameters ν[SUB]max[/SUB] and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between the average mass of RGB and RC stars is small, but significant [? (random) ±0.04 (systematic) M[SUB]&sun;[/SUB]]. Interestingly, such a small ? does not support scenarios of an extreme mass-loss for this metal-rich cluster. If we describe the mass-loss rate with Reimers prescription, a first comparison with isochrones suggests that the observed ? is compatible with a mass-loss efficiency parameter in the range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss rate are set by the analysis of the ˜2 Gyr old NGC 6819, largely due to the lower mass-loss expected for this cluster, and to the lack of an independent and accurate distance determination. In the near future, additional constraints from frequencies of individual pulsation modes and spectroscopic effective temperatures will allow further stringent tests of the Δν and ν[SUB]max[/SUB] scaling relations, which provide a novel, and potentially very accurate, means of determining stellar radii and masses. [less ▲]

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See detailAsteroseismology of red-clump stars with CoRoT and Kepler
Miglio, Andrea ULg; Montalban Iglesias, Josefa ULg; Eggenberger, P. et al

in AIP Conference Proceedings (2009), 1170

The availability of asteroseismic constraints for a large number of red giants with CoRoT and, in the near future with Kepler, paves the way for detailed studies of populations of galactic-disk red giants ... [more ▼]

The availability of asteroseismic constraints for a large number of red giants with CoRoT and, in the near future with Kepler, paves the way for detailed studies of populations of galactic-disk red giants. We investigate which information on the observed population can be recovered by the distribution of the observed seismic constraints: the frequency of maximum power of solar-like oscillations (νmax) and the large frequency separation (Δν). We use the distribution of νmax and of Δν observed by CoRoT in nearly 800 red giants in the first long observational run, as a tool to investigate the properties of galactic red-giant stars through the comparison with simulated distributions based on synthetic stellar populations. We can clearly identify the bulk of the red giants observed by CoRoT as red-clump stars, i.e. post-flash core-He-burning stars. The distribution of νmax and of Δν give us access to the distribution of the stellar radius and mass, and thus represent a most promising probe of the age and star formation rate of the disk, and of the mass-loss rate during the red-giant branch. This approach will be of great utility also in the interpretation of forthcoming surveys of variability of red giants with CoRoT and Kepler. In particular, an asteroseismic mass estimate of clump stars in the old-open clusters observed by Kepler, would represent a most valuable observational test of the poorly known mass-loss rate on the giant branch, and of its dependence on metallicity. [less ▲]

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See detailAsteroseismology of solar-type stars with Kepler I: Data analysis
Karoff, C.; Chaplin, W. J.; Appourchaux, T. et al

in Astronomische Nachrichten (2010), 331

We report on the first asteroseismic analysis of solar-type stars observed by Kepler. Observations of three G-type stars, made at one-minute cadence during the first 33.5 days of science operations ... [more ▼]

We report on the first asteroseismic analysis of solar-type stars observed by Kepler. Observations of three G-type stars, made at one-minute cadence during the first 33.5 days of science operations, reveal high signal-to-noise solar-like oscillation spectra in all three stars: About 20 modes of oscillation can clearly be distinguished in each star. We discuss the appearance of the oscillation spectra, including the presence of a possible signature of faculae, and the presence of mixed modes in one of the three stars. [less ▲]

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See detailAsteroseismology of solar-type stars with Kepler: III. Ground-based data
Molenda-Żakowicz, J.; Bruntt, H.; Sousa, S. et al

in Astronomische Nachrichten (2010), 331

We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more ... [more ▼]

We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than a thousand objects which are the subject of an intensive study by the Kepler Asteroseismic Science Consortium Working Group 1 (KASC WG-1). In the current work we will discuss the methods we use to determine the fundamental stellar atmospheric parameters using high-quality stellar spectra. These provide essential constraints for the asteroseismic modelling and make it possible to verify the parameters in the Kepler Input Catalogue (KIC). [less ▲]

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See detailAsteroseismology of the beta Cep star HD 129929. I. Observations, oscillation frequencies and stellar parameters
Aerts, C.; Waelkens, C.; Daszynska-Daszkiewicz, J. et al

in Astronomy and Astrophysics (2004), 415

We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V beta Cep star HD 129929. The dataset has a time base of 21.2 years. The occurrence of a ... [more ▼]

We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V beta Cep star HD 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies, among which we see components of two frequency multiplets with an average spacing of Ë 0.0121 c d[SUP]-1[/SUP] which points towards very slow rotation. This result is in agreement with new spectroscopic data of the star and also with previously taken UV spectra. We provide the amplitudes of the six frequencies in all seven photometric filters. The metal content of the star is Z=0.018± 0.004. All these observational results will be used to perform detailed seismic modelling of this massive star in a subsequent paper. Based on data gathered with the Swiss 0.7m telescope equipped with the photometer P7 of the Geneva Observatory and with the FEROS spectrograph attached to the ESO 2.2 m telescope, both situated at La Silla in Chile; the reduced photometric multicolour data are provided in Table 1, which is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/415/241 [less ▲]

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See detailAsteroseismology of the beta Cep star HD 129929. II. Seismic constraints on core overshooting, internal rotation and stellar parameters
Dupret, Marc-Antoine ULg; Thoul, Anne ULg; Scuflaire, Richard ULg et al

in Astronomy and Astrophysics (2004), 415

We perform a detailed seismic study of the beta Cep star HD 129929. Our analysis is based on the recent derivation of six pulsation frequencies. These frequencies are unambiguously identified from the ... [more ▼]

We perform a detailed seismic study of the beta Cep star HD 129929. Our analysis is based on the recent derivation of six pulsation frequencies. These frequencies are unambiguously identified from the seismic modelling and the photometric amplitudes to be the radial fundamental, the l=1, p[SUB]1[/SUB] triplet, two consecutive components of the l=2, g[SUB]1[/SUB] quintuplet. A non-adiabatic analysis allows us to constrain the metallicity of the star to Z \in [0.016, 0.022]. In addition, the fitting of three independent frequencies, two of which correspond to axisymmetric (m=0) modes, allows us to constrain the core overshooting parameter to alpha[SUB]ov[/SUB]=0.10 ± 0.05, as well as the other global parameters of the star. Finally, from the observation of the l=1 triplet and part of the l=2 quintuplet, we derive constraints on the internal rotation of this star. [less ▲]

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See detailAsteroseismology of the Beta Cephei star HD 129929. Effects of a change in the metal mixture
Thoul, Anne ULg; Scuflaire, Richard ULg; Ausseloos, M. et al

in Communications in Asteroseismology (2004), 144

We show that the constraints on the mass and on the rotation law in the envelope of the Beta Cephei star HD129929 are robust against a change in the metal mixture. The constraints on the metallicity and ... [more ▼]

We show that the constraints on the mass and on the rotation law in the envelope of the Beta Cephei star HD129929 are robust against a change in the metal mixture. The constraints on the metallicity and on the overshooting parameter, however, are dependent on the assumed metal mixture. [less ▲]

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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 ▲]

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See detailAsteroseismology of the β Cephei star KP Per
Saesen, S.; Briquet, Maryline ULg; Cuypers, J. et al

in Communications in Asteroseismology (2007), 150

We investigated the oscillations of the β Cephei star KP Per (HD 21803, B2IV, V=6.41) using Geneva photometry. We performed a detailed frequency analysis and a mode identification by means of photometric ... [more ▼]

We investigated the oscillations of the β Cephei star KP Per (HD 21803, B2IV, V=6.41) using Geneva photometry. We performed a detailed frequency analysis and a mode identification by means of photometric amplitude ratios. Then we confronted our deduced observational oscillation spectrum with that predicted by theory in order to determine a range for some stellar parameters, such as the mass and radius of KP Per. [less ▲]

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See detailAsteroseismology of the β Cephei star ν Eridani - III. Extended frequency analysis and mode identification
De Ridder, J.; Telting, J. H.; Balona, L. A. et al

in Monthly Notices of the Royal Astronomical Society (2004), 351

Using the large photometric and spectroscopic data sets of the ν Eridani multisite campaign given in our two recent papers (Aerts et al. and Handler et al.), we present an extended frequency analysis and ... [more ▼]

Using the large photometric and spectroscopic data sets of the ν Eridani multisite campaign given in our two recent papers (Aerts et al. and Handler et al.), we present an extended frequency analysis and a photometric mode identification. For the extended frequency analysis, we used an improved radial velocity time series, the second-moment time series and the line profiles themselves. In the radial velocity time series, we can now detect an additional pulsation frequency that was previously only found in photometric time series. We also report several new candidate pulsation frequencies. For seven frequencies, the photometric mode identification indicates that they belong to a radial mode and six dipole modes, and for three frequencies the degree l could not be unambiguously determined. We also placed ν Eri in the Hertzsprung-Russell diagram by determining T[SUB]eff[/SUB] using Geneva plus Strömgren photometric calibrations, spectral energy distribution fitting, by non-local thermodynamic equilibrium hydrogen, helium and silicon line profile fitting, and by determining log(L/L[SUB]solar[/SUB]) using the Hipparcos parallax and an Hβ calibration. [less ▲]

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See detailAsteroseismology of the β Cephei star ν Eridani: massive exploration of standard and non-standard stellar models to fit the oscillation data
Ausseloos, M.; Scuflaire, Richard ULg; Thoul, Anne ULg et al

in Monthly Notices of the Royal Astronomical Society (2004), 355

We present the results of a detailed seismic modelling of the β Cephei star ν Eridani with the Liège evolution and pulsation codes. We selected four clearly detected, well-identified and independent ... [more ▼]

We present the results of a detailed seismic modelling of the β Cephei star ν Eridani with the Liège evolution and pulsation codes. We selected four clearly detected, well-identified and independent pulsation modes from the frequency spectrum obtained from a recent five-month multisite, multitechnique campaign, while previous modelling work only took into account three frequencies. We show by means of a massive exploration of the parameter space that no standard stellar model both matches and excites these four observed modes, in contrast to the conclusion reached when considering only three frequencies. Therefore, we have considered stellar models with different metal mixtures and different initial hydrogen abundance values. We show that an increase in the relative number fraction of iron throughout the whole star or a large decrease in the initial hydrogen abundance make the stellar models matching the four selected modes satisfy all observational constraints and we provide the general properties of the best such physical models. [less ▲]

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See detailAsthénie et troubles visuels chez un peintre de 48 ans
Pirenne, Danièle ULg; Mairiaux, Philippe ULg

in Revue Médicale de Liège (2002), 57(12), 785-8

Tiredness is a common complaint which may have multiple causes, sometimes difficult to ascertain. As occupational activities can play a major role in the incidence of various diseases, failure to ... [more ▼]

Tiredness is a common complaint which may have multiple causes, sometimes difficult to ascertain. As occupational activities can play a major role in the incidence of various diseases, failure to investigate the patient's work history may hinder an adequate patient care. In the clinical case described hereafter, the patient symptoms could eventually be ascribed to a psycho-organic syndrome (POS) caused by the chronic exposure to organic solvents in the painting material used. This syndrome is non specific, evolves with time in an insidious manner, and, in its last stages, may cause non reversible brain damages. When facing non typical neurological symptoms in a working age adult, one has thus to consider the possibility of this diagnosis since the workers populations exposed to solvents are large in several occupations, and because the recent legal recognition in Belgium of this syndrome as an occupational disease does provide some interesting means for a better follow-up and protection of the patients concerned. [less ▲]

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See detailAsthme aigu grave: une affection qui demeure redoutable.
D'Orio, Virginie ULg; Ghuysen, Alexandre ULg; Lambermont, Bernard ULg

in Revue Médicale de Liège (2009), 64(7-8), 377-81

Severe exacerbations of asthma can be life-threatening if not aggressively treated. Despite the publication of therapeutic guidelines developed by experts in this field and people education programs ... [more ▼]

Severe exacerbations of asthma can be life-threatening if not aggressively treated. Despite the publication of therapeutic guidelines developed by experts in this field and people education programs, early recognition and characterization of patients at risk for fatal asthma remain scarce. We report the case of a young lady suffering from acute exacerbation of asthma responsible for intensive care admission with long term mechanical ventilation due to the lack in initial appropriate care. [less ▲]

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See detailAsthme et bêta2-agonistes de longue durée d'action
Bury, Thierry ULg; Kayambe, JM; Radermecker, Maurice ULg

in Médecine et Hygiène (1994), 52

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See detailAsthme et hyperréactivité bronchique non spécifique
Louis, Renaud ULg; Kayembe, J. M.; Radermecker, Maurice ULg

in Acta Clinica Belgica (1994), 49(3-4), 148-57

Bronchial hyperresponsiveness is a hallmark of asthma although it can also be present, to a lesser extent, in other diseases. The level of bronchial responsiveness depends on immuno-inflammatory processes ... [more ▼]

Bronchial hyperresponsiveness is a hallmark of asthma although it can also be present, to a lesser extent, in other diseases. The level of bronchial responsiveness depends on immuno-inflammatory processes modifying the functional status of airway smooth muscle as well as the structure of the bronchial wall. The responsiveness toward a direct constricting pharmacological agent is poorly correlated to the one toward an indirect constricting agent or a physical stimulus which cause airway obstruction through a more complex mechanism. Transversal studies show a relationship between the severity of asthma and the level of methacholine airway responsiveness. Long term treatment with corticoids can reduce the bronchial hyperresponsiveness of asthmatics. [less ▲]

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See detailAsthme et tabac.
Gusbin, N.; Garzaniti, N.; Louis, Renaud ULg

in Revue Médicale de Liège (2006), 61(2), 81-6

Roughly 40% of asthmatics are or have been smokers. These smoking asthmatics have been largely overlooked in the past. Tobacco is today considered as a risk factor for asthma and it seems that smoking ... [more ▼]

Roughly 40% of asthmatics are or have been smokers. These smoking asthmatics have been largely overlooked in the past. Tobacco is today considered as a risk factor for asthma and it seems that smoking asthmatics exhibit a different phenotype as compared to non smoking asthmatics. The inflammatory substrate differs widely, not only with respect to the type of cells present in the airways, but also with respect to the mediators brought into play. On the clinical point of view the asthma of smokers is also more severe that in non smokers, both at the symptomatic and the functional level. The asthma severity in smokers is partly linked to a resistance to inhaled corticoids, the cornerstone of maintenance treatment in asthma. This makes urgent to assess alternative treatment to inhaled corticoids for this asthma phenotype, but also emphasizes the need to support smoking cessation in asthmatics. [less ▲]

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See detailL'asthme ou le spectre asthmatique chez l'enfant
Battisti, Oreste ULg; Zigabe Mushamuka, Serge ULg

Learning material (2013)

ce travail présente les aspects cliniques, investigationnels, thérapeutiques et éducatifs du spectre asthmatique chez l'enfant

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