A comment on the metal abundance of the globular cluster M71

The Overall Abundances of Globular Clusters

“…Most of the critics of the high dispersion work did focus their criticism on the possibility of errors in continuum location, noting that the use of échelle spectrographs did make this problem a much more difficult one than it was with conventional spectra. Bell and Gustafsson (1982) remarked that there were systematic differences in equivalent width in lines in different échelle orders, in terms of how well they fitted the model atmosphere curve of growth. This problem may still be plaguing the analyses of the more metal rich stars.…”

“…This system has been analyzed by Bell and Gustafsson (1983) This system is a very interesting one, giving at least the possibility of searching for anomalies in the abundances of different elements. It is unfortunate that one or two galactic clusters were not observed in order to tie down the metal-rich end.…”

“…Rather than give a resume of current results for these indices, I simply refer to Bell and Gustafsson (1983) which gives plots of the abundance indicators versus abundances obtained from an analysis of Searle and Zinn's (1978) photometry, and go on to discuss a variant of this approach.…”

“…In order to do this, the following sets of results are intercompared: the high dispersion results, taken from Pilachowski (1984); the AS results, from Smith (1984b); the infra-red CM diagrams results; the Q39 results from Zinn (1980); results from (J-K) 0 , calibrated using the results of Bell and Gustafsson (1983). Some results from the TiO work of Mould are also quoted.…”

The Problem of Abundances for “Metal-Rich” Globular Clusters

“…Suggestions that the equivalent widths measured in echelle spectra are systematically wrong have been made (Bell, 1982;Bell and Gustafsson, 1982a) and contested (Pilachowski et al, 1982, cf., however, Bessell, 1982. The effects of the large reddening and the obvious risk for field-star contamination for the photometry of M 71 have been stressed (Cohen, 1980) but some arguments against this explanation have also been presented (Bell and Gustafsson, 1982a). Accurate narrowband photometry should be obtained for the cluster stars studied spectroscopically, in order to rule out some of this possible source of error.…”