Membership and other problems of the globular cluster M 22.
Abstract
Summary. Radial velocity observations of stars in M22 show that all the strong-lined stars in the field are non-members. Many of these stars are distinguishable from cluster members by their position in the B-V, V-IK diagram. There are no stars to the blue of the giant branch and brighter than V= 12.4 within 7 arcmin of the cluster centre. The presence of three hot stars fainter than this is typical of clusters with a very blue horizontal branch. The presence of CH-star features in 111-106 is confirmed. 111-78 appears to have stronger CN than other cluster members. The photometric and spectroscopic data suggest that M22 shows at most mild forms of the various peculiarities found in w Cen. Discussion of all available data suggests that V5 and three new variables lie on the giant branch while V8 lies slightly above and V9 slightly below the giant branch. Variability on the giant branch sets in at (B-V)0 = 1.44, (V-IK)o = 1.35, assuming a reddening of E(B-V) = 0.35 mag.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 1978
- DOI:
- 10.1093/mnras/182.2.293
- Bibcode:
- 1978MNRAS.182..293E