Avrett-Krook Model Atmosphere and the Continuous Absorption in the Violet and Ultraviolet Regions.

Abstract

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Avrett-Krook Model Atmosphere and the Continuous Absorption in the Violet and Ultraviolet Regions. Matsushima, Satoshi ; Terashita, Yoich I. Abstract Programs have been written for the IBM 7070 and 7040 to compute non-grey model atmospheres, following the iteration procedure recently developed by Avrett and Krook (Astrophys. J. 137, 874,1963). Application of the Avrett-Krook theory yields a model atmosphere strictly in radiative equilibrium. It was found that in general, only three iterations are sufficient to attain the flux constancy within the numerical fluctuations of the machine calculations. One of the purposes of our calculation is to examine the effect of absorption by quasi molecular hydrogen as a source of continuous opacity in the violet and ultraviolet regions (Zwann, C., Bull. Astron. Inst. Neth. 16, 225,1962). The effect of recent revisions of H- absorption coefficient by the Ohmuras (Phys. Rev. 121, 513,1961) and Gdtmari (Astrophys. J. 136, 935,1962) was also studied. In order to compare directly with observations, four models with different absorption coefficients were constructed. The difference between the model including only H and H- (Chandrasekhar) and the one with H and the revised H- absorption appeared to be insignificantly small. On the other hand, the inclusions of metals or metallic plus quasi-molecular hydrogen absorptions produced considerable effects in the final models, although the additional absorptions are sensitive only in the regions beyond the Balmar discontinuity. Except for the surface and the deepest layers, the molecular absorption predominates metallic absorption in the region between about XX 1600 and 4000 A, and the metals contribute only in the far ultraviolet region. The continuous spectrum at the center of the sun's disk computed from the model including both absorptions by metals and H2 molecule has shown a remarkable agreement with observations not only in the violet but in the visible regions, whereas the energy distributions predicted by three other models appeared too high in the violet and too low in the longer wavelength regions. Still about 15% lower theoretical intensities in the region XX 3700- 7000 A may be due to the omission of line-blanketing effect. If Erkovich's value for (H$H) absorption coefficient was truly an overestimate, as was suggested by Solomon in his criticism, our computations suggest that at least an additional source of opacity, ar exceeding that of metals, is needed to explain spectroscopic observations in the violet continuum of the solar-type stars. Publication: The Astronomical Journal Pub Date: March 1964 DOI: 10.1086/109245 Bibcode: 1964AJ.....69..143M full text sources ADS |