TYC 907-89-1 , the SIMBAD biblio

We present Washington CT₁T₂ photometry of a field central to the Boötes I dwarf spheroidal galaxy, which was discovered as a stellar overdensity in the Sloan Digital Sky Survey (DR5). We show that the Washington filters are much more effective than the Sloan filters in separating the metal-poor turn-off stars in the dwarf galaxy from the foreground stars. We detect 165 objects in the field, and statistically determine that just over 40% of the objects are nonmembers. Our statistical analysis mostly agrees with radial velocity measurements of the brighter stars. We find that there is a distinct main-sequence turn-off and subgiant branch, where there is some evidence of a spread in chemical abundance. Any evidence of an age spread is limited to a few billion years. The brightest seven Boötes I members give a (photometric-color derived) weighted mean iron abundance of [Fe/H] = -2.1^+0.3_–0.5, and the best-fit isochrone is the 14.1 Gyr, Z = 0.0002 model, with (m - M)_V = 19.11 and E(B - V) = 0.02.