Stellar chromospheres - H-alpha and CA II K profiles
نویسندگان
چکیده
منابع مشابه
A stellar perspective on chromospheres
The Sun is not alone in hosting a chromosphere: virtually all convective stars (Ftypes and later) possess them. Properties can vary wildly from object to object. Historically, three key systemic behaviors were recognized. First is the strong preference of chromospheres for the cool half of the H–R diagram. Second is the so-called rotation-age-activity connection (“Skumanich law”). Third is the ...
متن کاملMg II h + k emission lines as stellar activity indicators of main sequence F - K stars
Context. The largest dataset of stellar activity measurements available at present is the one obtained at the Mount Wilson Observatory, where high-precision Ca II H+K fluxes have been measured from 1966 for about 2200 stars. Since the Mg II h and k lines at λ2800 Å are formed in a similar way to the Ca II H+K emission lines, they are also good indicators of chromospheric structure. The Internat...
متن کاملModelling Chromospheric Line Profiles in NGC2808: Evidence of Mass Loss from RGB Stars
In this study we test the possibility that the asymmetry in the profiles of the Hα and Ca ii K lines in red giant stars is due to the presence of an active chromosphere rather than to mass loss. To this end, we compare line profiles computed using relevant model chromospheres to profiles of the Hα and Ca ii K lines observed in five red giant stars of the globular cluster NGC 2808. The spectra w...
متن کاملSimulations of Zeeman - split Ca II K - line Stokes profiles with angle - dependent partial redistribution
The formulation of the polarized radiative transfer equations for Zeeman-split spectral lines is still incomplete for cases with frequency-dependent line source function, e.g. when partial frequency distribution (PRD) of line photons occurs (strong resonance lines). Under the well-founded assumption that the field-free approximation works equally well for lines with partial redistribution as fo...
متن کاملRegulation of CA II and H+,K(+)-ATPase gene expression in canine gastric parietal cells.
Acid secretagogue-specific receptor activation in parietal cells triggers rapid and coordinate gene expression of gastric H+,K(+)-ATPase and of CA II. The rapid rise in steady-state levels of CA II mRNA is due to new transcription of the CA II gene in stimulated cells. Although the presumed function of CA II in activated parietal cells is to catalyze the generation of HCO3- from OH-, regulation...
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ژورنال
عنوان ژورنال: The Astrophysical Journal Supplement Series
سال: 1983
ISSN: 0067-0049,1538-4365
DOI: 10.1086/190911