Astron. Astrophys. Suppl. Ser. 144, 227-233
M. Geffert1,2 - G. Maintz1
Send offprint request: M. Geffert
1 - Sternwarte der Universität Bonn, Auf dem Hügel 71,
D-53121 Bonn, Germany
2 -
Observatoire de Bordeaux, URA 352 CNRS/INSU, BP. 89,
F-33270 Floirac, France
Received September 7, 1998; accepted March 7, 2000
We present the first results of a photometric and astrometric
investigation of stars in the region
of the globular cluster M 71 (NGC 6838). Using wide field
CCD observations we determined B and V magnitudes
of 4450 stars up to a limiting magnitude
of V
18.5 mag.
Relative proper motions were used to derive membership
probabilities for stars with
around the centre
of M 71. Our colour-magnitude diagram
(CMD) of 320 probable cluster members
reaches down to V = 18. A well defined red giant bump
- for the first time seen in M 71 - could be detected in our CMD.
From isochrone fitting we find M 71
metal poorer and older than previously assumed.
Four faint variable stars were confirmed
to be members of M 71. Moreover, we detected 13 blue
stragglers among our cluster members.
Key words: astrometry -- (stars:) blue stragglers -- (Galaxy:) globular clusters: individual: M 71
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