The old, metal-poor open cluster NGC 2243.
Abstract
Photoelectric UBV and photographic BV photometry of the Southern open cluster NGC 2243 is presented. The reddening and ultraviolet excess are determined by a general method which has been tested on several better- observed clusters. The adopted values for NGC 2243 are E(B-V) = orn.o6, (U-B)0.6 = + 0m.035 The latter result indicates a deficiency in heavy elements exceptional among open clusters. The metal abundance is estimated to be [Fe/H] = -0.5 relative to the Sun. The cluster CM diagram shows sparse giant andgiant branches and a giant branch clump or red horizontal branch containing about 10 stars at V = 13m.9 The upper main sequence is well defined and a gap appears therein notwithstanding the low heavyelement abundance and the unusually large age ( o + ) X I0 yr, deduced from the colour of the main sequence turn-off for an assumed helium abundance Y = . A distance modulus (m-M)o = 12 8 is derived but the luminosity of the zero-age main sequence is very uncertain for this composition. The adopted value implies that the cluster lies more than a kiloparsec from the galactic plane. The need for more detailed investigations of the cluster is stressed.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 1975
- DOI:
- 10.1093/mnras/173.3.801
- Bibcode:
- 1975MNRAS.173..801H