V553 CEN and a progression of bumps in BL HER light curves.

The assumption that the observed secondary bumps in the light curves of BL Herculis variables correspond to the Hertzsprung (1926) progression for classical Cepheids is used to determine the properties of V 553 Centauri and to discuss the bump pattern in the BL Her group. For V 553 Cen a mass of approximately 0.49 solar masses and a radius of approximately 9.9 solar radii are derived, values that seem to confirm this assumption. Theoretical period limits for the characteristic bump types are predicted and shown to be in good agreement with available observational data for BL Her stars.