Published online by Cambridge University Press: 15 February 2018
We have carried out simultaneous uvbyβ photometry for several RR Lyrae stars. For each of these stars, the observed m1 index variation along the pulsation cycle is compared with that expected variation from the (Δm1*,β) grids of Rodriguez et al. (1991) for the corresponding temperatures, gravities and metallicities. The m1 index variations are also calculated using the Kurucz's models. Good agreement is found