The variability of SPICA

Differential uvby observations of Spica are presented and analyzed. No coherent short-period light or colour index variations are found. An analysis of the ellipsoidal light variation leads to a new value of the radius of the primary component, which agrees very well with the radius determined by means of the Narrabri stellar intensity interferometer. The analysis also shows that the photometric data are consistent with the spectrographic period of the rotation of the line of apsides. In addition, recent hypotheses concerning the apparently extinct pulsations of the primary component are discussed. It is pointed out that the enhanced surface helium models of Cox (1985) predict pulsation constants substantially larger than the pulsation constant derived from the observationally determined mass and radius.