The first large-format CCD color-magnitude diagram (CMD) in the B and V passbands is presented for the Galactic globular cluster M53 (NGC 5024). The observations consist of 40 pairs of B and V CCD frames with FWHM <1′:.2. These frames were used to produce color-magnitude data for more than 20000 stars from the tip of the red giant-branch (RGB) to about two magnitudes below the main-sequence turnoff (V ∼ 22). The CMD reveals a classic example of a metal-poor stellar system, with the horizontal-branch (HB) predominantly blueward of the RR Lyrae instability strip and the relatively steep RGB. We have discovered 117 new blue straggler stars (BSSs) in the field of M53. The analysis of bright (V <19.39) BSSs clearly shows a bimodal radial distribution, with a high frequency in the inner and outer regions, but a distinct dip in the intermediate region. The distribution is similar to that found in M3, a globular cluster with similar central density and concentration. The relative age dating based on the color difference between the turnoff and the base of RGB reveals no significant age difference (Δt <1 Gyr) between M53 and M92.
|Journal||Journal of the Korean Physical Society|
|Issue number||SUPPL. 3|
|Publication status||Published - 1998 Dec 1|
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)