(delta) Sct-type nature of the variable V2109 Cyg

We present the results of simultaneous ...photometry carried out from 1999 to 2001 of the variable V2109 Cyg together with a spectroscopic analysis based on one high resolution spectrum obtained in 2000. From this study, the star is definitively classified as an evolved Sct-type variable with solar metal abundances. This conclusion is also supported by the detected multiperiodic pulsational behaviour and the observed variation of the m1 index over the pulsation cycle. This variation is slightly reversed relative to the V light curve, in very good agreement with the m1 variation expected from the photometric calibrations. Besides the main frequency f1=5.3745 cd -1 and its first harmonic 2f1, a secondary peak is found at f2=5.8332 cd -1 ( f1/f2=0.92) with f1 identified as a radial mode and f2 as non-radial. Whereas no significant variations are found in the amplitude of f1 from season to season, the amplitude of f2 changes strongly. Moreover, the main period has remained constant since 1990, within the observational uncertainties. Additional secondary frequencies may also be excited in this variable.