Cool giants and supergiants: chromospheres and winds
نویسندگان
چکیده
منابع مشابه
Observations of Chromospheres in Metal Deficient Field Giants
HST high resolution spectra of metal-deficient field giants more than double the stars in previous studies, span ∼ 3 magnitudes on the red giant branch, and sample an abundance range [Fe/H]=−1 to −3. These stars, in spite of their age and low metallicity, possess chromospheric fluxes of Mg II (λ2800) that are within a factor of 4 of Population I stars, and give signs of a dependence on the meta...
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The effects of rapid rotation and bi–stability upon the density contrast between the equatorial and polar directions of a B[e] supergiant are investigated. Based on a new slow solution for different high rotational radiation–driven winds and the fact that bi–stability allows a change in the line–force parameters (α, k, and δ), the equatorial densities are about 10–10 times higher than the polar...
متن کاملFast Winds and Mass Loss from Metal-Poor Field Giants
Echelle spectra of the infrared He I λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He I line is ubiquitous in stars with Teff & 4500K and MV fainter than −1.5, and reveals the dynamics of the atmosphere. The...
متن کاملRadii and Effective Temperatures for K and M Giants and Supergiants. Ii
We present new interferometric observations for 74 luminous red stars, made in the near-infrared. We show that our 2.2 km uniform-disk diameters agree with other near-infrared diameter determinations (lunar occultations and interferometers) for 22 stars measured in common with ours. From our new data, we derive e†ective temperatures that are compared with our previous work and with comparable o...
متن کاملRadii and Effective Temperatures for G, K, and M Giants and Supergiants
Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 69 giant and supergiant stars are presented. Spectral types of the 59 giant stars generally lie between G6 and M6, although a B7 giant is included ; the nine bright giants and supergiants have spectral types between F5 and M5. Comparison of the results to those from the IR Optical Telescope...
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ژورنال
عنوان ژورنال: Astronomy & Geophysics
سال: 1997
ISSN: 1366-8781,1468-4004
DOI: 10.1093/astrog/38.6.21