Activity cycles in RS CVn-type stars

Letter to the Editor Permanent active longitudes and activity cycles on RS CVn stars

A new analysis of the published long-term photometric observations has revealed permanent active-longitude structures in four RS CVn stars: EI Eri, II Peg, σ Gem, and HR 7275. Two active longitudes separated by half of the period are found to dominate on the surface during all available seasons. The positions of the longitudes on three stars (EI Eri, II Peg, HR 7275) are migrating in the orbita...

Long-term chromospheric activity of non-eclipsing RS CVn-type stars

Context. The IUE database provides a large number of UV high and low-resolution spectra of RS CVn-type stars from 1978 to 1996. In particular, many of these stars were monitored continuously during several seasons by IUE. Aims. Our main purpose is to study the short and long-term chromospheric activity of the RS CVn systems most observed by IUE: HD 22468 (V711 Tau, HR 1099, K1IV+G5V), HD 21242 ...

Quiescent and Flaring Structure in Rs Cvn

AM CVn stars

I review our observational and theoretical knowledge of AM CVn stars, focusing on recent developments. These include newly discovered systems, the possibility that two recently discovered extremely short period objects are AM CVn stars and an update on X-ray, UV an optical studies. Theoretical advances include the study of the details of both the donor and accretor, and the physics of the heliu...

Correlation Eeects in Microwave Observations of Selected Rs Cvn-like Stars

Sets of dual frequency microwave data on selected chromospherically active stars, from the Australia Telescope Compact Array, have been investigated for their auto and cross-correlation eeects. Comparison of cross-correlation peak values with theoretical expectation indicates a high degree of real physical connection between the emission at the pairs of frequencies (4.8 and 8.64-GHz) compared. ...