Chemical Separation vs Rotation in a and F-Stars
نویسندگان
چکیده
منابع مشابه
Differential Rotation in F Stars
Differential rotation can be detected in single line profiles of stars rotating more rapidly than about v sin i = 10 km s with the Fourier transform technique. This allows to search for differential rotation in large samples to look for correlations between differential rotation and other stellar parameters. I analyze the fraction of differentially rotating stars as a function of color, rotatio...
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We obtained high quality spectra of 135 stars of spectral types F and later and derived " overall " broadening functions in selected wavelength regions utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of the projected rotational velocity v sin i were derived from the first zero of the Fourier transformed profiles and the shapes of the profiles were analyzed for effects ...
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Ca II H and K high resolution observations for 60 evolved stars in the field and in 5 open clusters are presented. From these spectra chromospheric fluxes are derived, and a homogeneous sample of more than 100 giants is built adding data from the literature. In addition, for most stars, rotational velocities were derived from CORAVEL observations. By comparing chromospheric emission in the clus...
متن کاملAre metallic A - F giants evolved Am stars ? Rotation and rate of binaries among giant F stars ⋆ , ⋆ ⋆
We test the hypothesis of Berthet (1992) which foresees that Am stars become giant metallic A and F stars (defined by an enhanced value of the blanketing parameter ∆m 2 of the Geneva photometry) when they evolve. If this hypothesis is right, Am and metallic A-FIII stars need to have the same rate of binaries and a similar distribution of v sin i. From our new spectroscopic data and from v sin i...
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The smallest molecular cores observed to date have at least ∼6 orders of magnitude greater angular momentum per unit mass than the Sun, suggesting that they would greatly exceed the breakup velocity if no angular momentum was lost during the star formation process. Therefore, an angular momentum regulation mechanism must be at work in the pre-main-sequence phase, and disks are often invoked as ...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1993
ISSN: 0252-9211
DOI: 10.1017/s0252921100020923