Search Publications
Absolute magnitudes and kinematics of CP stars from HIPPARCOS data
Luri, X.; Figueras, F.; Torra, J. +5 more
The position in the HR diagram and the kinematic characteristics of different kinds of CP stars of the upper main sequence are obtained using the LM method of Luri et al. Most of the CP stars are main sequence stars occupying the whole width of the sequence. From a kinematic point of view, they belong to the young disk population (ages < 1.5 Gy…
Some recent results for the roAp stars
Kurtz, D. W.
Three topics are discussed: 1) Photometric observations of the rapidly oscillating Ap stars have shown that the pulsation amplitude drops dramatically as a function of wavelength from the blue to the red. A theoretical derivation, plus modelling, indicates that this is because the vertical wavelength of the pulsation mode is short compared to the …
The evolutionary state and fundamental parameters of metallic A-F giants
North, P.; Kunzli, M.; Erspamer, D.
Using Hipparcos parallaxes, we show that the metallic A-F giants found by Hauck on the basis of their high Delta m(2) index in Geneva photometry are on average more evolved than their non-metallic counterparts. Their mass distribution, rate of binaries and v sin i are shown to be incompatible with those of Am stars, so that they cannot be descenda…
On an ultraviolet spectral atlas of alpha2 CVn
Wahlgren, G. M.
We describe the ultraviolet spectra of the Ap star alpha 2 CVn that have been acquired with the Hubble Space Telescope and the nature of the optical region analyses for its rotational velocity and elemental abundances that have been undertaken in support of the ultraviolet data.
Determination of T(eff) and log G for A0 type stars and its impact on the interpretation of the HR diagram with the HIPPARCOS results
Gomez, A.; Gerbaldi, M.; Faraggiana, R. +3 more
The determination of the "Fundamental Parameters" T(eff) and log g for a set of dwarf A0-type stars is discussed in terms of consistency when comparing these values determined through different methods. The position of these stars in the HR diagram are discussed, taking into account the HIPPARCOS data. A large number of binary stars with component…
Atmospheric parameters and abundances of lambda Bootis stars
Heiter, U.
The results of the abundance analyses of six lambda Bootis stars are presented. For three stars, the impact of individual ODFs and various treatments of convection in the calculations of the model atmospheres are investigated.
CP stars: Photometric calibrations of luminosity using HIPPARCOS data
Jordi, C.; Luri, X.; Figueras, F. +7 more
The application of the Stromgren photometric luminosity calibrations to different types of CP stars is reexamined in the light of the new Hipparcos data. A first attempt is made to use the LM statistical parallax method - based on the maximum likelihood principle - to obtain a calibration of the absolute magnitude as a function of two Stromgren co…
The energy distribution of Beta CrB for the specific stellar abundances
Castelli, F.
The comparison of the observed and computed energy distributions of Beta CrB has shown that a model with the specific chemical composition of the star can account for the visual energy distribution, while it is still unable to reproduce ultraviolet observations shortward of 1700 Angstroms. Furthermore, the predicted absorption of strong Fe II and …
On the evolutionary status of lambda Bbootis stars using HIPPARCOS data
Paunzen, E.
Using the Hipparcos data, absolute magnitudes and thus the evolutionary status for the group of lambda Bootis stars were derived. The origin of this small group of non-magnetic, chemically peculiar stars, still remains a matter of debate. Using new evolutionary tracks, an age determination could be provided to distinguish between the two competing…