The globular cluster NGC 6809.
Abstract
A BV photometric investigation of the Southern Globular Cluster NGC 6809, was carried out using the 1 m telescope of Cerro La Silla (ESO) for the photoelectric work and the 1 m telescope of Cerro Las Campanas (CARSO) for the photographic work. Thirteen stars were observed photoelectrically, the limiting magnitude is V 16.12. Using this sequence 555 stars were measured photographically. The derived apparent distance modulus is (m-M) =1 . The reddening is E(B-V) = (Y 8. The true distance modulus is (m-M) = . The distance is 4.81 kpc from the sun and 1.90 kpc from the galactic plane. The main features of the colour-magnitude diagram are: the presence of a large sample of blue horizontal branch stars, a well defined gap in the horizontal branch, a steep and richly populated subgiant branch, and a deficiency of bright red giants. The giant branch rises 2w8 above the horizontal branch at (B-Y) = , characteristic of a rather metal poor object. Key words: globular cluster - BV photometry - horizontal branch
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- November 1975
- Bibcode:
- 1975A&AS...22..193A