Pulsating Variable Stars in the Coma Berenices dwarf spheroidal galaxy 1 (original) (raw)

We present B, V, I time-series photometry of the Coma Berenices dwarf spheroidal galaxy, a faint Milky Way satellite, recently discovered by the Sloan Digital Sky Survey. We have obtained V, B − V and V, V − I color-magnitude diagrams that reach V ∼ 23.0−23.2 mag showing the galaxy turnoff at V ∼ 21.7 mag, and have performed the first study of the variable star population of this new Milky Way companion. Two RR Lyrae stars (a fundamental-mode-RRaband a first overtone-RRc- pulsator) and a short period variable with period P=0.12468 days were identified in the galaxy. The RRab star has a rather long period of Pab = 0.66971 days and is about 0.2 mag brighter than the RRc variable and other non-variable stars on the galaxy horizontal branch. In the period-amplitude diagram the RRab variable falls closer to the loci of Oosterhoff 1 Based on data collected at the 1.52 m telescope of the INAF-Osservatorio Astronomico di Bologna,