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A microwave survey of southern active stars
The results of a survey of 153 active-chromosphere stars made with theParkes 64-m telescope at 5.0/8.4 GHz from 1981 to 1987 are reported.Microwave emission was detected from 70 stars on at least one occasion,with the highest detection rate of 68 percent from the RS CVn group. TheCa II stars and Algol-type binaries yielded detection rates of 44 and 30percent, respectively. The maximum powers emitted by the stars at5.0/8.4 GHz ranged over five orders of magnitude, with a median of 2.5 x10 to the 10th W/Hz. The maximum brightness temperatures had a smallerrange of three orders of magnitude, with a median of 3.6 x 10 to the 9thK.
| An H-alpha survey of southern hemisphere active chromosphere stars
Because of the variety of extraordinary phenomena exhibited by activechromosphere objects, discovery of new, bright surface-active stars isof considerable importance. Ca II emission is a well-known signature ofchromospheric activity, serving even as one of the points of definitionof the class of RS CVn binary stars. In connection with the presentinvestigation, spectroscopic observations of 27 Ca II emission starshave been conducted. The observations make it possible to identifyunambiguously the most chromospherically active stars in the sample. Byobserving the H-alpha line, rather than H and K, it is possible todistinguish nine of these stars which are likely to be observationaltargets as interesting as the extremely surface active objects V711 Tauor FK Com. Of the 27 stars surveyed, two (HD 86005, HD 204128) showedH-alpha as an emission feature above continuum, with estimatedequivalent width 1-2 A.
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