Stellar Effective Temperatures in the Spectral Range B6 to A0.

Abstract

The Avrett-Krook iteration procedure was used in conjunction with an IBM 7090 computer to construct, under the assumption of radiative, hydrostatic, and local thermodynamic equilibrium, a grid of stellar atmosphere models. The effective temperatures for these atmospheres ranged between 10 0000K and 20 0000K, while surface gravities were varied between 10~ and 10~. All known continuous opacity sources important in this temperature range were included in this grid. These models satisfy the condition of constant flux to within a few parts in 10~. A photoelectric scanner, designed by W. Liller, was used to obtain a series of spectrophotometric observations for a group of B-type stars in the Pleiades. I compared the wavelength variation of the emergent fluxes for my stellar atmospheres with these observations and deduced for each program star an effective temperature which carried an uncertainty of about 5000K. As a check on the validity of the procedure, the effective temperature, derived by matching the emergent flux for Vega with stellar models, was compared with the value obtained from the recent interferometric observations of the angular diameter of this star. The theoretical temperature of 95000K corresponds remarkably well with the experimental value. I combined with my observations the spectrophotometric data of Oke and Bless to establish a scale of effective temperatures in the spectral range B6 to A0. This scale was found to agree well except at A0 with that recently published by Harris [Harris, D. L.,in Vol. III of Stars and Stellar Systems, edited by K. Aa. Strand (University of Chicago Press, Chicago, 1963)J. The values of Te~~ were then correlated with (U- B)0 as a first step toward calibrating cluster color-magnitude arrays in terms of luminosity and effective temperature.