Comparing the Ca II H and the Ca II K Emission Lines in Giant Stars

Type Conference Paper
Names Jenna Ryon, M. Shetrone, G. Smith
Proceedings Title Bulletin of the American Astronomical Society
Conference Name American Astronomical Society, AAS Meeting #213, #408.08
Volume 41
Pages 206
Date January 1, 2009
Library Catalog NASA ADS
Abstract Measurements of the asymmetry of the emission peaks in the core of the Ca II H line for 105 giant stars are reported. The asymmetry is quantified with the parameter V/R, which is the ratio between the maximum number of counts in the blueward peak and the redward peak. The H and K lines probe the motion of certain chromospheric layers in the stellar atmosphere. Ca II K line V/R data are drawn from previous Smith & Shetrone papers and compared to the Ca II H line V/R data. It is found that the Ca II H line V/R ratio is +0.0387 larger than the K line ratio. The differences between the H and K line V/R parameters are also correlated with B-V color. Stars cooler than B-V = 1.2 are more likely to have H-K > 0 than H-K < 0, whereas the opposite is true for stars hotter than B-V = 1.2. We conclude that the discrepancies between the Ca II H and K line V/R values could be caused by the layers of chromospheric material that produce the double-peaked emission features simultaneously moving in opposite directions.
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