RR Lyrae stars in the Carina dwarf galaxy.

A large region of the Carina dwarf galaxy was searched for RR Lyrae stars using 'B' plates taken at the prime focus of the 4 m telescope at CTIO. The plates were scanned with a new high-speed plate scanner constructed at the NOAO offices in Tucson, and a new computer-based automated technique for 'blinking' plates was developed and used. 172 candidate variable stars were tagged. Light curves and periods could be obtained for 73 variables, and most are seen to be RR Lyrae stars. 58 of them are inferred to be members of the Carina galaxy. The mean period for the ab type variables is 0.62 days, intermediate between Oosterhoff groups I and II. Based on them, a distance modulus of 20.1 is derived for this galaxy. The presence of RR Lyraes in such large numbers suggests an underlying old population in the Carina dwarf galaxy. In addition, an unexpectedly large number of brighter foreground RR Lyrae stars were also found. The possible nature and origin of these stars is discussed; no conclusive inferences can be made at this time.