A new method for the analysis of equivalent widths and its application to solar photospheric oxygen |
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| Authors: | Richard C Altrock |
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| Institution: | (1) High Altitude Observatory and Dept. of Astro-Geophysics, University of Colorado, Boulder, Colo., U.S.A.;(2) Present address: Sacramento Peak Observatory, Sunspot, New Mexico |
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| Abstract: | Six neutral atomic oxygen Fraunhofer multiplets were observed at nine disk positions at Sacramento Peak Observatory. I filtered the data, corrected them for the instrumental profile and obtained equivalent widths.The equation of transfer for a plane-parallel atmosphere is solved to yield an expression for the equivalent width of a line or multiplet as a function of disk position; line source function, S
L, and relative population of the lower energy level of the transition. Comparison with the observations gives the abundance, average levels of formation of the lines and S
L.The numerical results show that the weak lines are formed either in L.T.E. or pure scattering (i.e., S
L  B
v
(T
e) J
c), but for  7770 Å S
L/B
(T
e) 0.6 ± 0.1 at  c = 0.1. An analysis of the central intensities of 7770 Å yields essentially the same results. The results for 8446 Å are not reliable due to a possible blend with an iron line. The abundance of oxygen in the photosphere may be slightly less than that found by previous investigators.The results are consistent with the assumption that all levels of photospheric oxygen are populated as in L.T.E. with the exception of 35S, which is overpopulated by approximately 50% at c = 0.1. The overpopulation may be due to the metastability of this level.Based on National Center for Atmospheric Research Cooperative Thesis No. 9. |
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