Abundance variations in the globular cluster M71 (NGC 6838)
Abstract
Context: Abundance variations in moderately metal-rich globular clusters can give clues about the formation and chemical enrichment of globular clusters.
Aims: CN, CH, Na, Mg and Al indices in spectra of 89 stars of the template metal-rich globular cluster M71 are measured and implications on internal mixing are discussed.
Methods: Stars from the turn-off up to the Red Giant Branch (0.87 < log g < 4.65) observed with the GMOS multi-object spectrograph at the Gemini-North telescope are analyzed. Radial velocities, colours, effective temperatures, gravities and spectral indices are determined for the sample.
Results: Previous findings related to the CN bimodality and CN-CH anticorrelation in stars of M71 are confirmed. We also find a CN-Na correlation, and Al-Na, as well as an Mg2-Al anticorrelation.
Conclusions: A combination of convective mixing and a primordial pollution by AGB or massive stars in the early stages of globular cluster formation is required to explain the observations.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 2008
- DOI:
- 10.1051/0004-6361:200809405
- arXiv:
- arXiv:0806.2629
- Bibcode:
- 2008A&A...486..941A
- Keywords:
-
- globular clusters: individual: M71;
- stars: abundances;
- stars: atmospheres;
- Galaxy: abundances;
- Astrophysics
- E-Print:
- Paper accepted for publication in Astronomy and Astrophysics