Variations in the maxima of long-period variables

On the basis of data from Studies of Long Period Variables by Campbell, an investigation has been made of the variations from cycle to cycle in the time of maximum and in the magnitude at maximum of 165 variable stars. A correlation was found between the difference in magnitude of two successive maxima and the time interval separating the maxima, in the sense that if the interval separating the maxima is less than average the second maximum tends to be the brighter of the two, and vice versa. Of the stars considered, 41% show such correlations with levels of significance of 95% or greater. The existence of this relationship does not appear to depend upon the period, spectral type, or space velocity of the star. Such an effect might be explained if we postulate that the light changes of these stars are associated with the outward propagation of disturbances taking more or less time to reach the surface depending upon the energy they carry.