The Profile of the Absorption Lines in Rotating Stars, Taking into Account the Variation of Ionization Due to Centrifugal Force

i. The investigations by Elvey * and Miss Westgate f have shown that a very great proportion of the stars of classes B and A have rotational velocities of the order of 100 km./sec., and that 5 per cent, of the early type stars have velocities larger than 200 km./sec. In several papers J Struve has indicated that in certain cases the centrifugal acceleration V*¡R may be of the same order as the surface gravity g, the ratio e = V^jRg having in quite reasonable stars a value approaching 0-5. Actually, a calculation of the ratio e for many B and A type stars of large rotational velocities gives values of the order of 0-4. The importance of these facts, in view of the mechanical instability of certain rotating stars as argued by Struve, is clear.