Infrared colors, CO band strengths, and physical parameters for giants in M71
Broad-band J, H, and K magnitudes and narrow-band CO and H_2O indices for 25 giant and horizontal-branch stars in the strong-lined globular cluster M71 are presented. These data are compared with similar data for M67 and for metal-poor globular clusters. In most photometric indices the M71 stars are intermediate between M67 and the metal-poor globulars, although the M71 giant branch extends to considerably cooler temperatures. Bolometric magnitudes and effective temperatures determined for the M71 stars also place this cluster between the other globulars and M67. A theoretical analysis of the CO indices indicates that M71 is metal deficient by 0.4 ( ± 0.2) dex in the mean with respect to field giants. The relationship between the CO indices and CN absorption strengths as determined from DDO photometry is as expected from empirically determined temperature dependences and theoretically determined abundance dependences.
Additional Information© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1978 May 1; accepted 1978 July 26. We thank Juan Carrasco and Gary Tuton for their assistance at the telescope. J. A. F. is grateful to Hale Observatories for guest observer privileges during the several observing runs required for this globular cluster project. We have had several informative conversations with Jeremy Mould and Olin Eggen. Several of our colleagues at CTIO have commented on an earlier draft of this paper. This work was supported in part by NSF grant AST 74-18555A2 and NASA grant NGL 05-002-207.
Published - 1979ApJ___227__499F.pdf