THE NEAR-IR NA-I DOUBLET AND CA-II TRIPLET IN LATE-TYPE STARS AND THE DETERMINATION OF STELLAR ATMOSPHERE PARAMETERS

CCD spectroscopic observations in the near-IR (7990-8680 angstrom) for a sample of 144 late type stars are presented. We investigate the dependence of the Na I doublet (lambda-8183 and 8194 angstrom) and the Ca II triplet (lambda-8498, 8542 and 8662 angstrom) on stellar atmospheric parameters. We confirm in stars of spectral types later than G0 a dependence of line strength on effective temperature, surface gravity and metallicity in good agreement with previous studies. However, our sample contains many more very late type stars than previous studies, and these stars show a strong dependence of Ca II triplet strength on temperature. These lines, together with the (R - I) colour index which is known to be a good temperature indicator, were used to estimate the metal abundance and the surface gravity of our program stars.