OPTICAL AND ULTRAVIOLET STUDIES OF STELLAR CHROMOSPHERES OF LAMBDA ANDROMEDAE AND OTHER LATE-TYPE STARS.

摘要

Chromospheric studies of the outer atmospheres of several late-type stars are presented along with a comprehensive study of (lamda) Andromedae, an "active chromosphere" star. Investigations were made of the chromospheric features of Ca II H and K, Mg II h and k, and other, high-temperature emissions accessible to the Copernicus and IUE satellites. Analogues to solar activity are consistent with the spectral behavior of the chromospheric indicators. The chromospheric activity and variability in Ca II H and K in (lamda) And are similar to sunspot and solar flare activity. In addition, a search was begun for short-timescale (few minutes) fluctuations in the H and K cores in several late-type stars.; Calibrated spectrophotometry for the Ca II K profiles and additional constraints provided by H(alpha) and the ultraviolet observations of Mg II and the high-temperature transition-region emissions were employed in the construction of semi-empirical chromospheric models of (lamda) And, (alpha) Aur, and (alpha) Boo. A prescription is given for models of active-chromosphere stars, which may also be useful for other late-type stars.