Narrow and broad-band photometry of red stars,.7 Luminosities and temperatures for halo-population red stars,of high luminosity.
(UB 17R1) observations of red giants in halo-population clusters are discussed. The clusters include 47 Tucanae, NGC 362, Centauri, NGC 5897, M4, MS, M92, NGC 6752, M22, and M2, as well as the old disk-population cluster M67. Some 20 variables in these clusters have also been observed, including two new variables at the tip of the giant branch in 47 Tucanae. Variable 162 in Centauri may not be variable, and Nos 6 7 and 164 in that cluster are probably field variables. The red variables, especially those with shorter periods (50-100 days) and small amplitudes, tend to lie above the giant branches of the clusters to which they belong. The regions of Cepheid and red-variable instability are well separated in the ( , R - 1)-plane. Four halo variables in the general field, S Car, R Pic, TV Vir, and CE Vir, are also discussed. TV Virginis is probably a member of Kapteyn's star group. With the exception of 47 Tucanae, the giant branches of these clusters roughly run from about = -3.6 mag at (R - I)o = +0.63 mag to - 1 mag near +0.28 mag, but there are variations from cluster to cluster in the slope of this branch. In general the mean values of A (U - B) derived for the cluster giants correlate well with other estimates of metal abundance. The range of A(U - B) values is from +0.1 mag for NGC 362 to +0.7 mag for M92 and NGC 5897. An (AI' , log T -diagram for the variable stars and representative giant branches has been obtained by using H. L. Johnson's calibration of the (R - I, log T -relation.