Stark-effect of the higher Balmer lines.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Stark-effect of the higher Balmer lines. van Dien, Elsa Abstract Computations have been carried through to obtain the profiles of the higher Balmer lines, especially to find the point where the lines merge into the continuum. The location of this point to the red side of the Balmer limit depends largely on pressure or surface-gravity, and to a smaller extent on the su~face-temperature. It was assumed that the lines are broadened by statical Stark-effect, the probability-distribu - tion W(P) of which has been given by Holtsmark' and by Verwey.2 As a simplification Dr. Pannekoek suggested to consider the lines spread out into a continuous band of width AX equal to the distance of the outer Stark components, rather than to consider the large number of components separately. The intensity of such bands is proportional to f-the oscillator strength-to W(fl) and to i/AX. By mechanical integration the absorption coefficients in their dependence on pressure and temperature were computed between X = 3660 and X = 3750. The f-values of Menzel and Pekeris1 were utilized. Then Eddington's equations for transfer of radiation were applied to compute the spectral energy distribution for a purely H atmosphere. The continuous absorption coefficients as given by Pannekoek4 were used. The computations were carried through for surface temperatures 100800, 126000 and 168000 (5040/T = 0.5, 0.4, 0.3 respectively) and at each of those for log gravity 2, 4, 6, 8. The computed disappearance of the discrete line-spectrum is given below. values for 5040/T log g 0.50 0.40 0.30 2 3671 3675 3675 4 3683 3691 3696 6 3697 3728 3735 8 >3750 >3750 The results have been compared with micro- photometer tracings made by Yfl at the Lick Observatory of a number of A stars, the temperatures of which had been carefully determined. Application of the mass-luminosity relation as given by Russell and Moore6 yielded all quanti- ties required for a comparison of the computations with observation. In general the agreement is quite satisfactory, especially for intermediate temperatures. Effective temperatures of 17,0000 for E UMa and ot CBr seem somewhat too high. For A~ stars the computed limit is too far in the ultraviolet; but here already a small amount of metals present in the atmosphere will influence the absorption considerably, and the absorption coefficients used are no longer applicable. I.Ann. Phys. Leipzig 58, 576, 1919. 2.Pub. Astr. Inst. Univ. Amsterdam No. 5, 1936. 3.M. N. 96, 77, 1935. 4.Pub. Astr. Inst. Univ. Amsterdam No. 4, 1935. 5.Lick Obs. Bull. 12, 104, 1926. 6.The Masses of the Stars, p. 112, 1940. Harvard College Observatory, Cambridge, Mass. Publication: The Astronomical Journal Pub Date: 1947 DOI: 10.1086/106029 Bibcode: 1947AJ.....52R.159V full text sources ADS |