منابع مشابه
Heavy calcium in CP stars★
Large wavelength shifts of infrared triplet lines of Ca ii have been observed in the spectra of HgMn and magnetic Ap stars. They have been attributed to the heavy calcium isotopes, including Ca. One member of the triplet, λ8542, had been either unavailable, or of poor quality in earlier spectra. The present material shows conclusively that the stellar λ8542 shifts are consistent with an interpr...
متن کاملOn the systematics of asteroseismological mass determinations of PG1159 stars
Aims. We analyze systematics in the asteroseismological mass determination methods in pulsating PG 1159 stars. Methods. We compare the seismic masses resulting from the comparison of the observed mean period spacings with the usually adopted asymptotic period spacings, ∆Πal , and the average of the computed period spacings, ∆Πl. Computations are based on full PG1159 evolutionary models with ste...
متن کاملStratification and isotope separation in CP stars
We investigate the elemental and isotopic stratification in the atmospheres of selected chemically peculiar (CP) stars of the upper main sequence. Reconfiguration of the UV-Visual Echelle Spectrograph in 2004 has made it possible to examine all three lines of the Ca II infrared (IR) triplet. Much of the material analysed was obtained in 2008. We support the claim of Ryabchikova, Kochukhov & Bag...
متن کاملDifferential rotation decay in the radiative envelopes of CP stars
Stars of spectral classes A and late B are almost entirely radiative. CP stars are a slowly rotating subgroup of these stars. It is possible that they possessed long-lived accretion disks in their T Tauri phase. Magnetic coupling of disk and star leads to rotational braking at the surface of the star. Microscopic viscosities are extremely small and will not be able to reduce the rotation rate o...
متن کاملThe Lorentz force in atmospheres of CP stars: 56 Arietis
Context. The presence of electric currents in the atmospheres of magnetic chemically peculiar (mCP) stars could bring important theoretical constrains about the nature and evolution of magnetic field in these stars. The Lorentz force, which results from the interaction between the magnetic field and the induced currents, modifies the atmospheric structure and induces characteristic rotational v...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1986
ISSN: 0252-9211
DOI: 10.1017/s0252921100091399