Search Publications
Variability analysis of δ Scuti candidate stars
Tautvaišienė, G.; Drazdauskas, A.; Mikolaitis, Š. +5 more
The Hipparcos catalogue contains stars suspected to be δ Scuti variables for which extensive groundbased observations and characterisation of variability are desired. We obtained 24 215 CCD images with the 35/51 cm Maksutov-type robotic telescope at the Molėtai Astronomical Observatory (MAO, Lithuania) of thirteen δ Scuti candidates selected from …
Orbital period changes in RW CrA, DX Vel and V0646 Cen
Chochol, D.; Mašek, M.; Volkov, I. M. +2 more
We aim to determine the absolute parameters of the components of southern Algol-type binaries with deep eclipses RW CrA, DX Vel, V0646 Cen and interpret their orbital period changes. The data analysis is based on a high quality Walraven photoelectric photometry, obtained in the 1960-70s, our recent CCD photometry, ASAS (Pojmanski, 2002), and Hippa…
Preliminary analysis of light curves of seven carbon stars
Mikulášek, Z.; Dušek, J.; Papoušek, J.
We present a preliminary analysis of the light curves of the following carbon stars: WZ Cas, VY UMa, Y CVn, RY Dra, T Lyr, HK Lyr and TT Cyg, constructed on the basis of our own BV photoelectric observations obtained at the Brno Observatory in 1979-94 and Hipparcos observations. The analysis suggests that "semiregular" light curves of all studied …
Photoelectric photometry of eclipsing contact binaries: U Peg, YY CrB, OU Ser and EQ Tau
Pribulla, T.; Vanko, M.
New photoelectric UBV observations of the eclipsing contact binary systems U Peg, YY CrB, OU Ser and EQ Tau obtained from August 2000 to October 2001 are presented and analyzed. The (O-C) diagram of U Peg indicates a decrease of the orbital period combined with a quasi-periodic variation. In the case of EQ Tau the long-term period changes can be i…
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…
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…
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…
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…