A photometric study of the field RR Lyrae stars AW Dra, AQ Lyr and CN Lyr

Abstract

We present CCD lightcurves for the three field RR Lyrae AQ Lyr, CN Lyr and AW Dra observed at the Teramo TNT telescope. Stellar temperatures have been derived from the observed mean colors, allowing a comparison with recent theoretical predictions on RR Lyrae lightcurves. As for the two metal rich pulsators in the sample we suggest that CN Lyr has been possibly misclassified, being a c-type pulsator. This gives a warning against the possible contamination with first overtone (FO) pulsators of observational samples of field ab type stars. On the other hand, if CN Lyr belongs to the low amplitude, b-type fundamental pulsators, it shows a lightcurve with a slow risetime not jet predicted by theory. AQ Lyrae appears as a metal rich ab type pulsator, with the expected luminosity but with amplitude lower than predicted by theory. Finally, we find that AW Dra behaves as a metal poor fundamental (F) pulsator, crossing the instability strip well above the corresponding Zero Age Horizontal Branch (ZAHB) luminosity level.