| 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, defined as the ratio between the maximum number of counts in the blueward peak and the redward peak of the emission profile. The Ca ii H and K emission lines probe the differential motion of certain chromospheric layers in the stellar atmosphere. Data on V/R for the Ca ii K line are drawn from previous papers and compared to the analogous H-line ratio, the H and K spectra being from the same sets of observations. It is found that the H-line (V/R)H value is +0.04 larger, on average, than the equivalent K-line ratio, however, the difference varies with B-V color. Red giants cooler than B-V=1.2 are more likely to have (V/R)H>(V/R)K, whereas the opposite is true for giants hotter than B-V=1.2. The differences between the Ca ii H and K-line asymmetries could be caused by the layers of chromospheric material from which these emission features arise moving with different velocities in an expanding outflow. |