CN ANOMALIES IN EXTREMELY METAL-DEFICIENT RED GIANTS

New photometric and ultraviolet spectroscopic data for the metal-deficient red giants CD -38-degrees-245 and BD -18-degrees-5550 are presented and discussed in light of recently noted photometric anomalies. From the IUE spectra it is apparent that the ultraviolet excess found in BD -18-degrees-5550 is not the result of a hot companion. The IUE spectra, in conjunction with other observations, point to anomalous nitrogen abundances as the source of the discrepancies between the photometric and spectroscopic abundances for these stars. CD -38-degrees-245 appears to be exceptionally nitrogen-rich while BD -18-degrees-5550 is anomalously nitrogen-poor with respect to stars of comparable metallicities. While BD -18-degrees-5550 appears to be an exception to the rule for its metallicity, the confirmation of a similar photometric pattern for CS 22885-96 may be an indication that the nitrogen overabundance in CD -38-degrees-245 is typical for giants of extreme metal-deficiency. Additionally, the IUE spectra exhibit evidence for emission in Mg II in CD -38-degrees-245. This indicator of chromospheric activity could be linked to the long-term variability observed in the hk index centered on Ca II H and K.