THE GAMMA-DORADUS-TYPE VARIABLE 9-AURIGAE - RESULTS FROM A MULTISITE CAMPAIGN

We present the results of a multi-longitude coordinated photometric ca mpaign on the gamma Dor variable 9 Aur. Three frequencies can be deter mined from the data (f(1) = 0.7948, f(3) = 0.7679, f(5) = 0.3429 d(-1) ); two of them have already been recognized in past seasons while the third frequency is reported for the first time. Analysis shows that th e third was 'turned off' or present with an amplitude below the limits of detection during previous observing seasons, This evidence, togeth er with consistent amplitude changes in the two previously recognized signals, suggests that the stellar structure responsible for 9 Aur's v ariability is extremely dynamic. Intermediate-resolution spectra and C ORAVEL radial velocities collected simultaneously show variability on time-scales commensurable with the photometry. The only sensible expla nation appears to be a non-radial pulsation (NRP) model, However, resu lts obtained reveal a number of features that deviate from classical N RP behaviour, Such features are emphasized in this paper in support of the future development of a specific NRP model - a model which has ye t to be elucidated for gamma Dor-type variables.