Late-type stars in M31 .2. C-, S-, and M-star spectra

We present spectra of AGE stars in M31 for which observations had been previously secured using a four-band photometric system (FBPS). The FBPS had been used to identify M-, S-, and carbon-star (C-star) candidates, and we use the spectra to show that the FBPS did an excellent job at identifying C- and M-stars. Of the 48 C-stars for which spectra were obtained, 7 have strongly enhanced C-13 bands (J-stars), 2 have strong Ha emission, while 3 are found to exhibit enhanced Li absorption (Li-stars). Both the J- and Li-stars are fainter than predicted by current theoretical models, while the colors of the H alpha stars suggest they may be in the terminal phases of their evolution. The C-2 and CN bandstrengths of the C-stars are measured, and no correlation between these bandstrengths and either M(bol) or (V-I) is found. It is suggested that this lack of correlation is due to an age spread. The spectra of the first confirmed S-star in M31 is presented, and two evolutionary pathways are suggested to account for this star's high luminosity. (C) 1996 American Astronomical Society.