Theγ Dor CoRoT target HD 49434 I-Results from the ground-based campaign

Context. We present the results of an extensive ground-based photometric and spectroscopic campaign on theγ Dor CoRoT target HD 49434. This campaign was preparatory to the CoRoT satellite observations, which took place from October 2007 to March 2008. Aims. Whereas satellite data will be limited to the detection of low-degree pulsation modes with poor identification (no filter s), ground-based data will provide eventually the identification of additional mo des and, through the spectroscopic data, detection of addit ional high-degree modes as well as an estimate of the azimuthal number m. Our aim was to detect and identify as many pulsation modes as possible from the ground-based dataset of theγ Dor star HD 49434, to anticipate the CoRoT results. Methods. We searched for frequencies in the multi-colour variations, the pixel-to-pixel variations across the line profiles and the moments varia- tions of a large dataset consisting of both multi-colour pho tometric and spectroscopic data from different observatories, using different frequency analysis methods. We performed a tentative mode identificat ion of the spectroscopic frequencies using the Moment Method and the Intensity Period Search Method. We also carried out an abundance analysis. Results. The frequency analysis clearly shows the presence of four frequencies in the 0.2-1.7 d−1 interval, as well as six frequencies in the 5-12 d−1 domain. The low frequencies are typical forγ Dor variables while the high frequencies are common forδ Sct pulsators. We propose the frequency 2.666 d−1 as a possible rotational frequency. All modes, for which an identification was possible, seem to be high-degree modes (3 ≤ℓ≤ 8). We did not find evidence for a possible binary nature of HD 49434. The element abundances we derived are consistent with the values obtained in previous analyses. Conclusions. We classify theγ Dor star HD 49434 as a hybrid pulsator, which pulsates simultaneously in p- and g-modes. This finding makes HD 49434 an extremely interesting target for asteroseismic modelling.