References of "Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society"
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See detailThe soundtrack of RR Lyrae in Omega Cen at high-frequency
Calamida, A.S.; Randall, S.K.; Monelli, M. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (in press)

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See detailLuhman 16AB: A Remarkable, Variable L/T Transition Binary 2 pc from the Sun
Burgasser, A. J.; Faherty, J.; Beletsky, Y. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2013)

Luhman (2013) has reported the discovery of a brown dwarf binary system only 2.01±0.15 pc from the Sun. The binary is well-resolved with a projected separation of 1farcs 5, and spectroscopic observations ... [more ▼]

Luhman (2013) has reported the discovery of a brown dwarf binary system only 2.01±0.15 pc from the Sun. The binary is well-resolved with a projected separation of 1farcs 5, and spectroscopic observations have identified the components as late-L and early-T dwarfs. The system exhibits several remarkable traits, including a ``flux reversal'', where the T dwarf is brighter over 0.9-1.3 mu m but fainter at other wavelengths; and significant (˜10%) short-period (˜4.9 hr) photometric variability with a complex light curve. These observations suggest spatial variations in condensate cloud structure, which is known to evolve substantially across the L dwarf/T dwarf transition. Here we report preliminary results from a multi-site monitoring campaign aimed at probing the spectral and temporal properties of this source. Focusing on our spectroscopic observations, we report the first detections of NIR spectral variability, present detailed analysis of K I lines that confirm differences in condensate opacity between the components; and preliminary determinations of radial and rotational velocities based on high-resolution NIR spectroscopy. [less ▲]

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See detailThe investigation of particle acceleration in colliding-wind massive binaries with SIMBOL-X.
De Becker, Michaël ULg; Rauw, Grégor ULg; Pittard, J. M. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2008), 79

An increasing number of early-type (O and Wolf-Rayet) colliding wind binaries (CWBs) is known to accelerate particles up to relativistic energies. In this context, non-thermal emission processes such as ... [more ▼]

An increasing number of early-type (O and Wolf-Rayet) colliding wind binaries (CWBs) is known to accelerate particles up to relativistic energies. In this context, non-thermal emission processes such as inverse Compton (IC) scattering are expected to produce a high energy spectrum, in addition to the strong thermal emission from the shock-heated plasma. SIMBOL-X will be the ideal observatory to investigate the hard X-ray spectrum (above 10 keV) of these systems, i.e. where it is no longer dominated by the thermal emission. Such observations are strongly needed to constrain the models aimed at understanding the physics of particle acceleration in CWB. Such systems are important laboratories for investigating the underlying physics of particle acceleration at high Mach number shocks, and probe a different region of parameter space than studies of supernova remnants. [less ▲]

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See detailStudy of the QSO HE0354-5500 with combined HST imaging and VLT spectroscopy . An example of a deconvolution-based method for probing the QSOs host galaxies characteristics
Letawe, Yannick ULg; Magain, Pierre ULg; Letawe, Géraldine ULg et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2008), 79

The host galaxy of the QSO HE0354-5500 (M_B=-24.7, z=0.2674) is studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The morphology and dynamics of the host ... [more ▼]

The host galaxy of the QSO HE0354-5500 (M_B=-24.7, z=0.2674) is studied on the basis of high resolution HST optical images and spatially resolved VLT slit spectra. The morphology and dynamics of the host are described. The gas ionization and velocity are mapped as a function of the distance to the central QSO. Reflection or scattering of the QSO Halpha line from remote regions of the galaxy is detected. The line shifts show that the matter responsible for the light reflection moves away from the QSO, likely accelerated by its radiation pressure. Moreover, different resolved emission regions are found in the central kpc, both in the images and the spectra. [less ▲]

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See detailObservational results for northern and southern (candidate) gamma Doradus stars .
De Cat, P.; Goossens, K.; Bouckaert, F. et al

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

We report on observational results obtained for 78 objects originally classified as bona-fide or candidate gamma Doradus stars. For the southern objects, we gathered echelle spectra with the CORALIE ... [more ▼]

We report on observational results obtained for 78 objects originally classified as bona-fide or candidate gamma Doradus stars. For the southern objects, we gathered echelle spectra with the CORALIE spectrograph attached to the Euler telescope in 1998-2003 and/or Johnson-Cousins B,V,I_c observations with the MODULAR photometer attached to the 0.5-m SAAO telescope in 1999-2000. For the northern objects, we obtained Geneva U,B,B_1,B_2,V,V_1,G observations with the P7 photometer attached to the 1.2-m Mercator telescope in 2001-2004. At least 15 of our objects are binaries, of which 7 are new. For 6 binaries, we determined the orbit for the first time. At least 17 objects show profile variations and at least 12 objects are multiperiodic photometric variables. Our results allow us to upgrade 11 objects to bona-fide gamma Doradus stars and to downgrade 8 objects to constant up to the current detection limits. Mode identification is still ongoing, but so far, only l = 1 and 2 modes have been identified. [less ▲]

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See detailRS Cha, a binary system suitable for testing stellar physics modeling during the pre-main sequence phase.
Alecian, E.; Catala, C.; Goupil, Marie-José et al

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

We use accurate spectroscopic data of the pre-main sequence eclipsing binary system RS Cha to redetermine masses and radii of both components and to measure the metallicity of the system. Knowing all ... [more ▼]

We use accurate spectroscopic data of the pre-main sequence eclipsing binary system RS Cha to redetermine masses and radii of both components and to measure the metallicity of the system. Knowing all fundamental parameters of both stars we are able to test stellar physics modeling during the PMS phase. We find no evidence that our models are deficient. Accurate detection of modes and measurements of periods of the recently discovered pulsations in both components are required to constrain more severely the physical description of PMS stellar models.. [less ▲]

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See detailApplication of time-dependent convection models to the photometric mode identification in delta Scuti stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

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

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène \cite{Grigahcene} to the mode identification and seismic study of delta Sct stars. We compare the non ... [more ▼]

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène \cite{Grigahcene} to the mode identification and seismic study of delta Sct stars. We compare the non-adiabatic phase-lags obtained with TDC and Frozen Convection (FC) treatments and show that they are very different at the red side of the instability strip. Finally, we compare the phase differences between light and velocity curves observed for the star 1 Mon with the theoretical predictions of TDC and FC models. The much better agreement found with the TDC models enables us to identify the modes of this star with a higher degree of confidency. [less ▲]

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See detailInfluence of overshooting and metallicity on the delta Scuti and gamma Doradus instability strips
Grigahcène, A.; Dupret, Marc-Antoine ULg; Garrido, R. et al

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

Computations of theoretical instability strips (IS) for delta Scuti (Sct) and gamma Dor (Dor) stars are presented. The Time-Dependent Convection (TDC) theory of Gabriel (1996) and Grigahcène et al. (2005 ... [more ▼]

Computations of theoretical instability strips (IS) for delta Scuti (Sct) and gamma Dor (Dor) stars are presented. The Time-Dependent Convection (TDC) theory of Gabriel (1996) and Grigahcène et al. (2005) is adopted in our models. We are able to obtain the delta Sct and gamma Dor IS. We present a prospective study on the influence of the overshooting and metallicity on the location of these IS in the HR diagram. [less ▲]

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See detailApplication of time-dependent convection models to the photometric mode identification in gamma Doradus stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

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

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene} to the photometric mode identification in gamma Dor stars. Comparison of our ... [more ▼]

We apply the Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene} to the photometric mode identification in gamma Dor stars. Comparison of our theoretical results with the observed amplitudes and phases of the star gamma Dor is presented. This comparison makes the identification of the degree l of its pulsation modes possible and shows that our TDC models better agree with observations than Frozen Convection (FC) models. [less ▲]

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See detailTheoretical Aspects of g-mode Pulsations in gamma Doradus Stars
Dupret, Marc-Antoine ULg; Grigahcène, A.; Garrido, R. et al

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

gamma Dor stars are main sequence variable A-F stars whose long periods (between 0.35 and 3 days) correspond to high-order gravity modes pulsation. Most of them are multiperiodic. We will concentrate here ... [more ▼]

gamma Dor stars are main sequence variable A-F stars whose long periods (between 0.35 and 3 days) correspond to high-order gravity modes pulsation. Most of them are multiperiodic. We will concentrate here on two theoretical aspects of these stars. First, an analysis of the driving mechanism of the gamma Dor g-modes is presented, using the linear Time-Dependent Convection (TDC) treatment of Gabriel \cite{Gabriel1996} and Grigahcène et al. \cite{Grigahcene}. This driving is due to a periodic flux blocking mechanism at the base of their convective envelope. The location of the blue and red edges of their instability strip as well as the periods range of their observed modes is explained by the balance between this driving mechanism and radiative damping in the g-mode cavity. Secondly, the multi-color photometric amplitude ratios and the phase differences between the light and velocity curves are considered. It is shown that the agreement between theory and observations obtained with TDC models is much better than with Frozen Convection (FC) models. The theoretical analysis of these observables makes the photometric identification of the degree l of the modes possible and gives constraints on the characteristics of the convective envelope of these stars. Finally, the attractive potential of gamma Dor stars as targets for asteroseismology is considered. [less ▲]

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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 ▲]

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See detailAccretion from AGB winds.
Thoul, Anne ULg; Jorissen, A.; Goriely, S. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2000), 71

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See detailInfluence of opacities, partition functions and hydrogen diffusion on the 5 min solar oscillations
Gabriel, Maurice ULg; Noels-Grötsch, Arlette ULg; Scuflaire, Richard ULg

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (1984), 55(1-2), 169-174

Several accuracy tests of the frequencies computation have been performed. They show that for a given model, the frequencies have errors lower than 2 micro-Hz. Several tests have also been made on the ... [more ▼]

Several accuracy tests of the frequencies computation have been performed. They show that for a given model, the frequencies have errors lower than 2 micro-Hz. Several tests have also been made on the Henyey code. They show that the use of the same opacity formula as Bahcall et al. (1983) allows to reproduce their model with a good accuracy. The model has however frequencies systematically 12 micro-Hz larger than found by Ulrich and Rhodes. A model with diffusion of H and He has also been studied. Its frequencies are nearly the same as those of the standard model. [less ▲]

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See detailInfluence of the equations of state and of the z value on the solar oscillations
Shibahashi, H.; Noels-Grötsch, Arlette ULg; Gabriel, Maurice ULg

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (1984), 55

The authors have evolved the standard solar models taking account of the electrostatic correction in the equations of state and the Los Alamos Opacity Library, and computed their eigenfrequencies for p ... [more ▼]

The authors have evolved the standard solar models taking account of the electrostatic correction in the equations of state and the Los Alamos Opacity Library, and computed their eigenfrequencies for p-mode and g-mode oscillations. The contribution of that correction to the pressure is up to several percent in the convective zone, and the present equilibrium models thus obtained have deeper convective zones than the conventional models. These improvements in the equilibrium model reduce the discrepancies between the theoretical frequencies and the observations concurrently for p-mode oscillations with low and high degree l. Theoretical frequencies of g-modes with low l are significantly higher than the observational ones. [less ▲]

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