The Period and the Cause of Variability of the Magnetic Ap Star V473 Tauri

The ground based UBV observations and Hipparcos Hp magnitudes of this well known magnetic variable are analyzed. The period of the star's light variation is improved. The improved value, accounting for the available photometric data from the 1963-1964 Lowell observations of Rakosch to the 1990-1993 Hp magnitudes, is equal to 1.4068541±0.0000029 d. The effective temperature and bolometric correction are then derived from the de-reddened B-V color index and the star is plotted in the theoretical H-R diagram using the luminosity obtained from the Hipparcos parallax. Finally, the cause of variability of V473 Tau is discussed in terms of two propositions: (1) the oblique rotator model, and (2) pulsation in a high radial-order g-mode. Hitherto unpublished UBV photometry of V473 Tau is presented in the Appendix.