منابع مشابه
On the Hipparcos parallaxes of O stars
We compare the absolute visual magnitude of the majority of bright O stars in the sky as predicted from their spectral type with the absolute magnitude calculated from their apparent magnitude and the Hipparcos parallax. We find that many stars appear to be much fainter than expected, up to five magnitudes. We find no evidence for a correlation between magnitude differences and the stellar rota...
متن کاملHipparcos parallaxes and the nature of δ Scuti stars ?
Hipparcos parallaxes give new tests of the nature of δ Sct variables. For many individual stars accurate distances are now available, i.e. directly determined luminosities and radii can be used to test theoretical models. Of particular interest are the at present very unclear relations between high–amplitude δ Sct stars and the much more abundant low–amplitude δ Sct variables, and the relations...
متن کاملThe absolute magnitudes of RR Lyrae stars from HIPPARCOS parallaxes ?
Using the method of “reduced parallaxes” for the Halo RR Lyrae stars in the hipparcos catalogue we derive a zero point of 0.77 ± 0.26 mag for an assumed slope of 0.18 in the MV-[Fe/H] relation. This is 0.28 magnitude brighter than the value Fernley et al. (1998a) derived by employing the method of statistical parallax for the identical sample and using the same slope. We point out that a simila...
متن کاملSurface gravities of very metal-poor stars from Hipparcos parallaxes
Wediscuss some consequences for the determination of the surface gravity parameter of very metal-poor halo dwarfs in the new light shed upon these objects from the Hipparcos astrometry. Whereas it has become clear that standard spectroscopic LTE iron ionization equilibria are prone to systematic errors, in the sense, that stages of evolution are predicted that are actually not yet reached, the ...
متن کاملHipparcos Parallaxes and the Cepheid Distance Scale
Hipparcos parallaxes have recently become available for a sample of Galactic Cepheids, and we have used these new distances to calibrate the Cepheid periodluminosity (PL) relation at six wavelengths (BV IJHK). Comparing these calibrations with previously published multiwavelength PL relations we find agreement to within 0.07 ± 0.14 mag, or 4 ±7% in distance. Unfortunately, the current parallax ...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2004
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361:20047185