1997A&A...325..563S

On the basis of almost 1500 uvby photometric observations of θ Tucanae collected in 1993, we discuss the colour variation of this multi-periodic δ Scuti star and debate some of its binary and pulsational properties. The frequencies f₁=0.281 and f₂=0.142c/d embody orbital motion in a 7.04d day ellipsoidal configuration characterised by a light curve with unequal maxima and minima and a colour index that becomes bluer during the minimum phases. The first results of an analysis of the light curve points towards a mass ratio q of the order of 0.10-0.15. We present dependable numerical values for colour phase differences and amplitude ratios A_b–y/A_y, φ_b–y-φ_y, A_v–y/A_y, φ_v–y-φ_y and A_u–y/A_y, φ_u–y-φ_y which can be used for pulsation-mode identification. The principal pulsation frequency f₇=20.28c/d is reconcilable with a radial mode.