Coordinated multiwavelength observations of the RS CVn system CF Tuc

The relatively bright eclipsing RS CVn binary CF Tuc was observed in both o ptical (photometry and spectroscopy) and microwave ranges in a 'multisite, multiwavelength' campaign in 1996. The microwave data, gathered using the Australia Telescope Compact Array,co vered slightly more than one complete orbital cycle at 4.8 and 8.64 GHz in one continuous nm. There was also limited coverage at 1.38 and 2.38 GHz. Hi gh-dispersion spectroscopy was obtained using the McLellan 1-m telescope an d echelle spectrograph at Mt John University Observatory (New Zealand). Sup porting photometry came from smaller scale facilities associated with the R oyal Astronomical Society of New Zealand (RASNZ), The data show the correlation between microwave signal enhancement and phot ometric flux diminution (maculation effect) noted previously in similar stu dies. The spectroscopy also points to the phenomena being related to a very enhanced active region on the secondary star located close to the maculati on region. Cross-correlation of the microwave emission data between the 4.8- and 8.64- GHz ranges shows a strong positive correlation, with a significant lag of t he 4.8-GHz behind the 8.64-GHz variations. This indicates energized waves p ropagating through the corona of the K4 subgiant at the electron sound spee d. The emitting region may have been eclipsed bye primary star, but such ec lipse effects are of marginal significance for the present analysis. An attempt is made to put all the evidence into one coherent picture of the active region.