Maia variables and upper-main-sequence phenomena.

A sample of four stars, including Maia itself, which are located within the Maia instability strip are investigated for photometric variability. The data consist of over 1600 differential Stromgren y-magnitudes collected during 11 nights of observation. No evidence is found for variability over the 0.1-0.3-day period range suggested for Maia stars. Two stars, Merope and Atlas, do seem to show variability, but the lengths of their periods imply a closer relation to the 53 Persei stars. It is suggested that the Maia stars do not exist as a separate class of variable stars but are an extension of the 53 Persei phenomenon to cooler temperatures. Convective core overshooting is hypothesized to be the mechanism responsible for the variability of these stars. It is noted that this process has also been found to be necessary in cluster isochrone dating analyses, in the formation of the blue straggler stars, in the explanation of the apsidal motion of alpha Vir, and as the instability mechanism for the beta Canis Majoris stars.