Involved people at OAB: Bragaglia, Clementini, Di Fabrizio, Merighi, Tosi.
The photometric and spectroscopic study of a sample of RR Lyrae variables which exhibit anomalous scatter and large amplitude variation of their light curves is continuing [in collaboration with Carretta and Gratton (OAPd), Ivans and Sneden (Texas Un.), Marconi (OAN), Smith (MSU), and Wilhelm (Southwestern Un.)]. Continuated/adjacent photometric data are being collected with the 1.52m telescope in Loiano, the 60 cm of the Michigan State University and the 40 cm of the Southwestern University, while high resolution spectroscopic data, covering one full pulsation cycle of the variables has been secured with the 2.7 m telescope of the McDonald Observatory. We have already discovered among the stars in our sample a new field double-mode RR Lyrae : CU Comae [Clementini et al. (2000, AJ, in press)]. This is the sixth such RRd identified to date in the field of our Galaxy, and is the most metal-poor ever detected ([Fe/H]=-2.34).