The ζ Herculis, σ Puppis, ∊ Indi, and η Cephei Groups of Old Disk Population Stars

In the light of a previous discussion of two large groups (Wolf 630 and 61 Cygni) of old disk population stars, the possible members of four smaller groups, which had been isolated by various means, were subjected to the same analysis. Stars rejected from these groups on the basis of data now available are listed and (UBVRI) photometry of the remaining, as well as many new, members is discussed. (R, I) results are also presented for the subgiant and giant members of several old disk population clusters. The resulting color-luminosity arrays are very similar to those for the Wolf 630 and 61 Cyg groups although some variation in the giant branches is noted. The major revision of previous results is in the changed V velocity for the oPuppis group, which removes the anomalous color-luminosity array previously found, although this group still contains stars with ultraviolet excesses larger than those known for any other disk group or cluster. A comparison between the group and H and K emission width luminosities suggests that either a half dozen stars now assigned to the groups are nonmembers or that systematic errors may arise in the values of v (K) for old disk stars on the vertical subgiant branch in the (Mb0l, RI) plane. A close correlation is found between the values of Mv (Group) - Mv (K) and (R- I) for several of the group members. The red variables in these groups are very similar to those in the Wolf 630 and 61 Cyg groups and the one variable in the old disk cluster NGC 6940.