Abstract
Lines formed in a differentially expanding atmosphere have been calculated by using the angle averaged redistribution functionR I (Hummer, 1962). We have compared these lines, in a few cases, with those formed by complete redistribution in the observer's frame of reference. We have considered an atmosphere whose ratios of inner to outer radii are 2 and 10, and it is assumed that the gas in the atmosphere is expanding uniformly with a maximum velocity of 3 mean thermal units. We have presented lines formed in spherical symmetry and those obtained by integrating over the apparent disc. Three types of physical situations are considered with a 2-level atom with non-LTE approximation (1) ε=10−4, β=10−4, (2) ε=10−4, β=0 and (3) ε=β=0, where ε is the probability per scatter that a photon is destroyed by collisional de-excitation, and β is the ratioKc/Kl of absorption in the continuum per unit frequency interval to that in the line centre.
It is found that there are noticeable differences between the profiles formed by partial redistribution (PRD) and complete redistribution (CRD). The profiles integrated over the stellar disc from the first type of the media are box type with flat top, which are similar to those observed in WC stars and those from the second type of media show emission peaks on red and blue sides with emission on the red side larger than the one on the blue side. The profiles from the third type of media with pure scattering, show some emission on the red side and deep absorption on the blue side. Large geometrical extensions of the atmosphere and higher gas velocities seem to enhance these two effects.
Similar content being viewed by others
References
Abhyankar, K. D.: 1964,Astrophys. J. 140, 1353.
Bappu, M. K. V.: 1973, ‘Wolf-Rayet and High Temperature Stars’, in M. K. V. Bappu and J. Sahade (eds),IAU Symposium, No. 49, p. 59, D. Reidel Publishing Company.
Cannon, C. J. and Vardavas, I. M.: 1974,Astron. Astrophys. 32, 85.
Chandrasekhar, S.: 1945,Astrophys. J. 102, 402.
Hummer, D. G.: 1962,Monthly Notices Roy. Astron. Soc. 125, 21.
Jefferies, J. T.: 1968,Spectral Line Formation, Blaisdell Publishing Company.
Kuhi, L. V.: 1973, ‘Wolf-Rayet and High-Temperature Stars’, in M. K. V. Bappu and J. Sahade (eds),IAU Symposium No. 49, p. 205, D. Reidel Publishing Company.
Kunasz, P. B. and Hummer, D. G.: 1974,Monthly Notices Roy. Astron. Soc. 166, 57.
McCrea, W. and Mitra, K.: 1936,Z. Astrophys. 11, 359.
Mihalas, D.: 1978,Stellar Atmospheres, Second Edition, Freeman Publishing Company.
Mihalas, D., Kunasz, P. B., and Hummer, D. G.: 1976,Astrophys. J. 210 250.
Peraiah, A.: 1978a,Astrophys. Space Sci. 58, 189.
Peraiah, A.: 1978b,Kodaikanal Obs. Bull. 2, 115.
Peraiah, A. and Wehrse, R.: 1978,Astron. Astrophys. 70, 213.
Vardavas, I. M.: 1974,J. Quant. Spectr. Radiative Transfer 14, 909.
Vardavas, I. M.: 1976,J. Quant. Spectr. Radiative Transfer 16, 781.
Wehrse, R. and Peraiah, A.: 1979,Astron. Astrophys. 71, 289.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Peraiah, A. Line formation in spherical media with partial frequency redistribution. Astrophys Space Sci 63, 267–277 (1979). https://doi.org/10.1007/BF00638902
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00638902