Effective temperatures and surface gravities of metallic-line A stars

New effective temperatures have been derived for a group of classical Am stars using line-blanketed model atmospheres and ultraviolet energy distributions. The effective temperatures are systematically cooler than previous determinations; the Am stars extend from 6600 K, nearly 1000 K cooler than found previously, to 10,000 K. The models with solar composition provide the best fit, with the possible exception of the two hottest stars in the sample. Energy distributions and effective temperatures are used to predict angular diameters for the program stars. In an Appendix, an analysis is conducted of Sirius, showing that a model with (M/H) = +1.0 provides the best match to its total energy distribution. It is also shown that the atmosphere of Sirius is deficient in helium by at least a factor of 10.