The Continuous Spectrum of Model Stellar Atmospheres.

Abstract

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Continuous Spectrum of Model Stellar Atmospheres. Williamson, Ralph E. Abstract On the assumption that atomic hydrogen and the negative hydrogen ion are the oniy sources of con- tinuous opacity in stellar atmospheres, the properties of the continuous spectra of twelve model atmos- pheres characterized by various values of the effective temperature Te and the average electron pressure p6, are investigated. An improved value of the atomic continuous absorption coefficient for H is used in the computations. Approximate values for the Rosseland mean absorption coefficients ~ are derived for a wide range of the parameters p6 and Te and for the twelve model atmospheres (with 10 ~ ~ 1O~; 56000 ~ Te ~ 10,0800); the monochromatic mass-absorption coefficients Ky are calculated for a number of Se- lected frequencies covering a wave-length range of 2500-10,000 A. The ratio i/Ky is used to determine the logarithm of the ratio of the monochromatic flux F~ through each model atmosphere to the black-body flux F9(e) corresponding to Te for the atmosphere. Color temperatures for regions 3300-3650 A, 3850- 4550 A, and 5550-7150 A, as well as the magnitudes of the Balmer and the Paschen discontinuities in the continuous spectrum, are computed for each of the model atmospheres. Comparison of the calculated val- ues of the Balmer discontinuity with observations of this quantity indicate a value of Pe = 10~ for stars of spectral types A and a somewhat smaller value for stars of type F. Plots of the reciprocal color tempera- ture EL~ = 5O4O/T~ in three spectral regions, as a function of e, = SO4O/Te for observations on stars, for the models here considered, and for those of Wildt, who used older values of the absorption coefficient of H (both the latter for P~ = 103), show that the agreement of theory and observation has been improved by the present calculations. In general, the agreement with the observations is less satisfactory in the longer wave lengths. It is shown that the present models predict some increase of T~ with frequency for the visual and near infrared, while the observations of Williams and of Hall show a slight decrease of T~ with frequency. The magnitude of the Paschen discontinuity for Vega as observed by Hall and Wiffiams is satisfactorily predicted by an appropriate model (~ = 0.5, p6 = ~103) Publication: The Astrophysical Journal Pub Date: January 1943 DOI: 10.1086/144491 Bibcode: 1943ApJ....97...51W full text sources ADS |