Photometry of NGC 5053

The horizontal branch (HB) is predominantly blueward of the RR Lyrae instability strip and the slope of the red giant branch (RGB) is relatively steep, both characteristic of a metal-poor system. Monte- Carlo simulations show that both the RGB and HB are underpopulated relative to those of the metal-poor cluster M15, indicative of the relatively lower total luminosity of NGC 5053.

Based on the mean magnitude of stars located at the red and blue edges of the instability strip, we find V(HB) = 16.65 +/- 0.03. At this magnitude, polynomial fits to the cluster RGBs in the two measured colors yield (B-V)_g = 0.71 +/- 0.016 and (V-I)_g = 0.93 +/- 0.016. Using the BVI two-color diagram in a differential manner with respect to M68 and M15 gives a reddening of E(B-V) = 0.06 +/- 0.02 for NGC 5053.