M5 RR Lyrae times of maxima

This provides a time baseline of up to 118 yr for these variables. The analysis was performed using two independent approaches: first, the classical O-C behaviour of the time of maximum light, and second, via a grid (P, {beta}), where the solution producing the minimum scatter in the phased light curve is chosen.

The results of the two methods agree satisfactorily. This allowed a new interpretation of the nature of the period changes in many RR Lyrae stars in M5. It is found that in 96 per cent of the stars studied no irregular or stochastic variations need to be claimed, but that 66 per cent of the population shows steady period increases or decreases, and that 34 per cent of the periods seem to have been stable over the last century.