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See detailA pulsating auroral X-ray hot spot on Jupiter
Gladstone, G. R.; Waite, J. H.; Grodent, Denis ULg et al

in Nature (2002), 415(6875), 1000-1003

Jupiter's X-ray aurora has been thought to be excited by energetic sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions(1-3). Here we report high-spatial ... [more ▼]

Jupiter's X-ray aurora has been thought to be excited by energetic sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions(1-3). Here we report high-spatial-resolution observations that demonstrate that most of Jupiter's northern auroral X-rays come from a 'hot spot' located significantly poleward of the latitudes connected to the inner magnetosphere. The hot spot seems to be fixed in magnetic latitude and longitude and occurs in a region where anomalous infrared(4-7) and ultraviolet(8) emissions have also been observed. We infer from the data that the particles that excite the aurora originate in the outer magnetosphere. The hot spot X-rays pulsate with an approximately 45-min period, a period similar to that reported for high-latitude radio and energetic electron bursts observed by near-Jupiter spacecraft(9,10). These results invalidate the idea that jovian auroral X-ray emissions are mainly excited by steady precipitation of energetic heavy ions from the inner magnetosphere. Instead, the X-rays seem to result from currently unexplained processes in the outer magnetosphere that produce highly localized and highly variable emissions over an extremely wide range of wavelengths. [less ▲]

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See detailPulsating B-type Stars in the Open Cluster NGC 884: Frequencies, Mode Identification, and Asteroseismology
Saesen, S.; Briquet, Maryline ULg; Aerts, C. et al

in Astronomical Journal (2013), 146

Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars ... [more ▼]

Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance, and chemical composition. We present an observational asteroseismology study based on the discovery of numerous multi-periodic and mono-periodic B stars in the open cluster NGC 884. We describe a thorough investigation of the pulsational properties of all B-type stars in the cluster. Overall, our detailed frequency analysis resulted in 115 detected frequencies in 65 stars. We found 36 mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic stars and one star with nine independent frequencies. We also derived the amplitudes and phases of all detected frequencies in the U, B, V, and I filter, if available. We achieved unambiguous identifications of the mode degree for 12 of the detected frequencies in nine of the pulsators. Imposing the identified degrees and measured frequencies of the radial, dipole, and quadrupole modes of five pulsators led to a seismic cluster age estimate of log (age/yr) = 7.12-7.28 from a comparison with stellar models. Our study is a proof-of-concept for and illustrates the current status of ensemble asteroseismology of a young open cluster. [less ▲]

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See detailA pulsation zoo in the hot subdwarf B star KIC 10139564 observed by Kepler
Baran, A.S.; Reed, M.D.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 424

We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B (sdB) star ... [more ▼]

We present our analyses of 15 months of Kepler data on KIC 10139564. We detected 57 periodicities with a variety of properties not previously observed all together in one pulsating subdwarf B (sdB) star. Ten of the periodicities were found in the low-frequency region, and we associate them with nonradial g modes. The other periodicities were found in the high-frequency region, which are likely p modes. We discovered that most of the periodicities are components of multiplets with a common spacing. Assuming that multiplets are caused by rotation, we derive a rotation period of 25.6 ± 1.8 d. The multiplets also allow us to identify the pulsations to an unprecedented extent for this class of pulsator. We also detect l ≥ 2 multiplets, which are sensitive to the pulsation inclination and can constrain limb darkening via geometric cancellation factors. While most periodicities are stable, we detected several regions that show complex patterns. Detailed analyses showed that these regions are complicated by several factors. Two are combination frequencies that originate in the super-Nyquist region and were found to be reflected below the Nyquist frequency. The Fourier peaks are clear in the super-Nyquist region, but the orbital motion of Kepler smears the Nyquist frequency in the barycentric reference frame and this effect is passed on to the sub-Nyquist reflections. Others are likely multiplets but unstable in amplitudes and/or frequencies. The density of periodicities also makes KIC 10139564 challenging to explain using published models. This menagerie of properties should provide tight constraints on structural models, making this sdB star the most promising for applying asteroseismology. To support our photometric analysis, we have obtained spectroscopic radial-velocity measurements of KIC 10139564 using low-resolution spectra in the Balmer-line region. We did not find any radial-velocity variation. We used our high signal-to-noise average spectrum to improve the atmospheric parameters of the sdB star, deriving Teff = 31 859 K and log g = 5.673 dex. Based also on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. [less ▲]

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See detailPulsational analysis of the Herbig Ae star HD 140237
Fumel, Aurélie ULg; Böhm, Torsten

in Communications in Asteroseismology (2008), 157

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See detailPulsational Mode Identification Based on Chromatic Amplitude Behaviour: Recent Results for Rapidly Oscillating Subdwarf B Stars
Randall, Suzanna K; Fontaine, Gilles; Brassard, Pierre et al

in Astronomical Society of the Pacific Conference Series (2012, September), 462(232),

We present recent results from mode identification based on the amplitude-wavelength behaviour for three rapidly pulsating subdwarf B stars: HS 2201+2610, EC 11583-2708 and EC 20338-1925.

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See detailPulsational Mode Identification Based on Chromatic Amplitude Behaviour: Recent Results for Rapidly Oscillating Subdwarf B Stars
Randall, S.K.; Fontaine, G.; Brassard, P. et al

in Astronomical Society of the Pacific Conference Series (2012, October), 462

We present recent results from mode identification based on the amplitude-wavelength behaviour for three rapidly pulsating subdwarf B stars: HS 2201+2610, EC 11583–2708 and EC 20338–1925.

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See detailPulsations du cœur de Scyllium catulus en l’absence d’urée
Fredericq, Léon ULg

in Archives Internationales de Physiologie (1922), XIX

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See detailPulsations in massive stars: effect of the atmosphere on the strange mode pulsations
Godart, Mélanie ULg; Dupret, Marc-Antoine ULg; Noels-Grötsch, Arlette ULg et al

in Proceedings of the International Astronomical Union (2011), 272

Recent space observations with CoRoT and ground-based spectroscopy have shown the presence of different types of pulsations in OB stars. These oscillations could be due to acoustic and gravity modes ... [more ▼]

Recent space observations with CoRoT and ground-based spectroscopy have shown the presence of different types of pulsations in OB stars. These oscillations could be due to acoustic and gravity modes, solar-like oscillations or even other pulsations of large growth rates. We present a first attempt at interpreting the latter as strange modes. [less ▲]

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See detailPulsations in O and B stars
Godart, Mélanie ULg

Conference (2010, June)

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See detailPulsations in white dwarf stars
Fontaine, Gilles; Bergeron, Pierre; Brassard, Pierre et al

in Proceedings of the International Astronomical Union (2014, February), 301

We first present a brief description of the six distinct families of pulsating white dwarfs that are now known. These are all opacity-driven pulsators showing low- to mid-order, low-degree gravity modes ... [more ▼]

We first present a brief description of the six distinct families of pulsating white dwarfs that are now known. These are all opacity-driven pulsators showing low- to mid-order, low-degree gravity modes. We then discuss some recent highlights that have come up in the field of white dwarf asteroseismology. [less ▲]

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See detailPulsations of an Evolved Self-consistently Distorted Star
Ouazzani, Rhita-Maria ULg; Dupret, Marc-Antoine ULg; Roxburgh, I. W. et al

in ASP Conference Proceeding, Vol. 462, 402 (2012, September 01)

A new two-dimensional (2D) non-perturbative method to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distortion of ... [more ▼]

A new two-dimensional (2D) non-perturbative method to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distortion of the star while the non-perturbative method includes the full influence of the Coriolis acceleration, and are used to compute oscillation modes of rapid rotators — high-order p-modes in δ Scuti stars, as well as low-order p- and g-modes in β Cephei stars. We compare the oscillation spectra obtained for centrifugally distorted polytropes with those of Reese et al. (2006), and give the first results for a realistic 2D model of a rapidly rotating 2 M[SUB]&sun;[/SUB] evolved star computed with the method developed by Roxburgh (2006). [less ▲]

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See detailPulsations of rapidly rotating evolved stars
Ouazzani, Rhita-Maria ULg; Roxburgh, I. W.; Dupret, Marc-Antoine ULg

in proceedings of the 20th Stellar Pulsation Conference Series, Granada sept 2011 (2012), 1301

A new two dimensional non-perturbative code to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distorsion of the star ... [more ▼]

A new two dimensional non-perturbative code to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distorsion of the star while the non perturbative method includes the full influence of the Coriolis acceleration. This 2D non-perturbative code is used to study pulsational spectra of highly distorted evolved models of stars. 2D models of stars are obtained by a self consistent method which distorts spherically averaged stellar models a posteriori. We are also able to compute gravito-acoustic modes for the first time in rapidly rotating stars. We present the dynamics of pulsation modes in such models, and show regularities in their frequency spectra. [less ▲]

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See detailPulsations of rapidly rotating stars. I. The ACOR numerical code
Ouazzani, Rhita-Maria ULg; Dupret, Marc-Antoine ULg; Reese, Daniel ULg

in Astronomy and Astrophysics (2012), 547

Context. Very high precision seismic space missions such as CoRoT and Kepler provide the means of testing the modeling of transport processes in stellar interiors. For some stars, such as solar-like and ... [more ▼]

Context. Very high precision seismic space missions such as CoRoT and Kepler provide the means of testing the modeling of transport processes in stellar interiors. For some stars, such as solar-like and red giant stars, a rotational splitting is measured. However, to fully exploit these splittings and constrain the rotation profile, one needs to be able to calculate them accurately. For some other stars, such as δ Scuti and Be stars, for instance, the observed pulsation spectra are modified by rotation to such an extent that a perturbative treatment of the effects of rotation is no longer valid. <BR /> Aims: We present here a new two-dimensional non-perturbative code called ACOR (adiabatic code of oscillation including rotation) that allows us to compute adiabatic non-radial pulsations of rotating stars without making any assumptions on the sphericity of the star, the fluid properties (i.e., baroclinicity) or the rotation profile. <BR /> Methods: The 2D non-perturbative calculations fully take into account the centrifugal distortion of the star and include the full influence of the Coriolis acceleration. The numerical method is based on a spectral approach for the angular part of the modes and a fourth-order finite differences approach for the radial part. <BR /> Results: We test and evaluate the accuracy of the calculations by comparing them with those coming from the TOP (two-dimensional oscillation program) for the same polytropic models. We illustrate the effects of rapid rotation on stellar pulsations through the phenomenon of avoided crossings. <BR /> Conclusions: As shown by the comparison with the TOP for simple models, the code is stable, and gives accurate results up to near-critical rotation rates. [less ▲]

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See detailPulse pressure and ambulatory arterial stiffness index (AASI) in patients wit type 1 diabetes
Philips, Jean-Christophe ULg; Marchand, Monique ULg; Saint-Remy, Annie ULg et al

Conference (2009, September 19)

Results of PP and AASI measurements performed during a 24H AMBP recording and a 3 min posture test are not superimposable, but gave complementary information, in a population with type 1 diabetes mellitus ... [more ▼]

Results of PP and AASI measurements performed during a 24H AMBP recording and a 3 min posture test are not superimposable, but gave complementary information, in a population with type 1 diabetes mellitus. Our proof-of-concept study does not support the use of AASI as a cardiovascular risk marker when calculated during a short posture test. [less ▲]

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See detailPulse pressure and cardiovascular autonomic neuropathy according to duration of type 1 diabetes.
Philips, Jean-Christophe ULg; Marchand, Monique ULg; Scheen, André ULg

in Diabetes/Metabolism Research & Reviews (2009)

BACKGROUND: To evaluate changes in pulse pressure (PP) and markers of cardiovascular autonomic neuropathy (CAN) according to duration of type 1 diabetes mellitus (T1DM). METHODS: This cross-sectional ... [more ▼]

BACKGROUND: To evaluate changes in pulse pressure (PP) and markers of cardiovascular autonomic neuropathy (CAN) according to duration of type 1 diabetes mellitus (T1DM). METHODS: This cross-sectional controlled study evaluated 159 diabetic patients during a 3-min posture test (standing-squatting-standing) with continuous measurement of systolic (SBP), diastolic (DBP) and mean (MBP) blood pressure by a Finapres device. Arterial stiffness was indirectly assessed by PP and the slope of PP as a function of MBP calculated during the whole 3-min test. CAN was assessed by the expiration/inspiration pulse interval ratio (E/I R-R ratio) during deep breathing and by three indices measured during the squatting test. Patients were divided into four groups according to diabetes duration (<10 years, 11-20 years, 21-30 years and > 30 years from group 1 to group 4, respectively) and compared with age-matched non-diabetic subjects. RESULTS: PP progressively increased (p < 0.0001) and PP/MBP decreased (p < 0.0005) according to T1DM duration, whereas these parameters remained almost unchanged in age-matched control subjects. E/I ratio (p < 0.0001) and baroreflex gain (p < 0.0005) progressively decreased with T1DM duration. The parasympathetic index (squatting test vagal ratio-SqTv) significantly increased (p < 0.0001), whereas the sympathetic index (squatting test sympathetic ratio-SqTs) only tended to decrease (p = 0.12) according to diabetes duration. No such changes in CAN indices were observed in the non-diabetic population. CONCLUSIONS: PP increased according to T1DM duration in an age range where PP remained almost stable in controls, in agreement with accelerated arterial stiffening due to chronic hyperglycaemia. The baroreflex gain decreased and other indices of CAN also deteriorated with diabetes duration, more so indices reflecting parasympathetic rather than sympathetic dysfunction. [less ▲]

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See detailPulse pressure and pulsatile stress in overweight/obese nonhypertensive patients with versus without type 2 diabetes.
Scheen, André ULg; Philips, Jean-Christophe ULg; Marchand, Monique ULg

in Obesity Reviews : An Official Journal of the International Association for the Study of Obesity (2010)

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See detailPulse pressure and pulsatile stress in overweight/obese patients versus lean subjects in absence of hypertension or diabetes.
Scheen, André ULg; Philips, Jean-Christophe ULg; Marchand, Monique ULg

in Obesity Reviews : An Official Journal of the International Association for the Study of Obesity (2010)

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See detailPulse pressure and pulse wave velocity as markers of arterial stiffness in patients with type 1 diabetes
Philips, Jean-Christophe ULg; Xhignesse, Patricia ULg; Marchand, Monique ULg et al

Conference (2009, October 19)

Type 1 diabetes was associated with an increase in both PP and PWV as compared to a nondiabetic population. In the diabetic population, a close correlation between the two indirect markers of arterial ... [more ▼]

Type 1 diabetes was associated with an increase in both PP and PWV as compared to a nondiabetic population. In the diabetic population, a close correlation between the two indirect markers of arterial stiffness was found and also between each of them and age (or diabetes duration), but not in controls. These observations support the concept of an earier arterial stiffness in type 1 diabetes with rather poor glycemic control. [less ▲]

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See detailPulsed holographic interferometry with photorefractive crystals. Recent advances of the european “PHIFE” project
Georges, Marc ULg; Lemaire, Philippe; Pauliat, Gilles et al

Conference (2004, March)

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