The Magnitude of the Sun, the Stellar Temperature Scale, and Bolometric Corrections.

Abstract

Three connected subjects are treated in this paper. The first section deals with the effective temperature, the absolute photovisual and bolometric magnitudes, and the spectral type of the sun. The quantities adopted are: T e =.5713° (Unsold) ; Afpv = 4.73; Mbol = 4.62; spectrum dG2. The second section contains a discussion of T e of the O, B, and A stars. The result is given in Table 3 and shown in Figure 1. In the third section, tables of bolometric correction are constructed, as far as possible independently of assumptions about the shape of the spectral energy-curves. For spectral types earlier than Fo, theoretical spectral energy-curves are used; the results are found in Tables 6 and 3. For later types, empirical bolometric corrections are derived from Pettit and Nicholson's radiometric observations. The discussion is based on Table 7 and Figures 2 and 3; the result is given in Tables 9 and 10. In the fourth section, effective temperatures are derived for late-type stars with suitable data: Castor C and the giants for which diameters were measured interfero-metrically. Limb darkening has been taken into account. The result for Castor C is 3550 ± iio°; for the giants, the values in Table 11. In the last section, color temperatures are collected and reduced to the system of effective temperatures. Particular attention is paid to the observations of the dwarfs (Tables 12 and 14), on which the reduction to effective temperatures depends to a large extent (sun). Table 13, last column, gives the derived effective temperatures for classes AM ; they are shown graphically in Figure 4. Directions are given for the calibration of temperatures derived from W. Becker's Catalogue of color indices and Pettit and Nicholson's water-cell absorptions, to effective temperatures (p. 469). Two applications are given. The result on e Aurigae reduces a difficulty previously encountered by B. Strömgren. INTRODUCTION The purpose of this article is the selection or derivation of the most probable set of effective temperatures and of bolometric corrections that can now be obtained. These data are required in the discussion of the mass-luminosity relation given in the following paper. Only a few new results are derived here, but the main object is to select and relate the most reliable observations and results thus far obtained. Among the recent investigations of the temperature scale, those by Pannekoek 1 and Pilowski 2 are of special interest. The results of Pannekoek's paper are extensively used in our article. Pilowski's pa-1 Ap. 84,481, 1936. 2 Zs.f.Ap., ii, 265, 1936. 429