Variable Stars in the Newly Discovered Milky Way Dwarf Spheroidal Satellite Canes Venatici I

Abstract

We have identified 23 RR Lyrae stars and three possible anomalous Cepheids (ACs) among 84 candidate variables in the recently discovered Canes Venatici I (CVn I) dwarf spheroidal galaxy. The mean period of 18 RRab type stars, --> Pab = 0.60 ± 0.01 days, and the location of these stars in the period-amplitude diagram suggest that CVn I is likely an Oosterhoff-intermediate system. The average apparent magnitude of the RR Lyrae stars, --> V = 22.17 ± 0.02 mag, gives a distance of 210 -->+ 7−5 kpc, for an adopted reddening -->E(B − V) = 0.03 mag. We present a B, V color-magnitude diagram (CMD) of CVn I that reaches -->V ~ 25 mag, and shows that the galaxy has a mainly old stellar population with a metal abundance near [Fe/H] = –2.0 dex. The width of the red giant branch and the location of the candidate ACs on the CMD may indicate that the galaxy hosts a complex stellar population with stars from ~13 Gyr to as young as ~0.6 Gyr.