A Compact Population of Red Giants in the Blue Compact Dwarf Galaxy UGCA 290

We present HST/WFPC2 single-star photometry for the blue dwarf galaxy UGCA290, whose morphology is intermediate between classic iE Blue Compact Dwarfsand blue dwarfs which exhibit no red background sheet of older stars. Thecolor-magnitude diagram of this galaxy in V and I, extending over sixmagnitudes, is remarkably similar to that of the star-forming region in the iEBlue Compact Dwarf VII Zw 403. There is no evidence for gaps in itsstar-formation history over the last billion years, and the color of its redgiant branch indicates a very metal-poor stellar population. From the magnitudeof the tip of the red giant branch, we derive a distance of 6.7 Mpc, more thantwice the distance estimated from the brightest blue supergiants.Comment: 10 pages, 3 color figures, LaTeX2e. Accepted for publication in ApJ Letter