Sensitivity of the Hα line to expansion, geometrical extent and temperature gradient in the G and K supergiant chromospheres

  • Sushma V. Mallik
Re-examining the Corona/Wind Dividing Line
Part of the Lecture Notes in Physics book series (LNP, volume 291)


We report on preliminary results of new radiative transfer calculations of Hα in differentially expanding nonisothermal spherical chromospheres, including explicitly the effects of ionization.

The Hα line in late G and K supergiants is a very strong absorption feature with a blue displaced core. Small emission components are often seen on either or both sides of the absorption profile. In an earlier paper (Mallik 1986), detailed Hα transfer calculations were reported for an isothermal chromosphere and line profiles were computed using a comoving frame transfer code developed by Peraiah (1980, 1981). Because Hα is mainly Doppler broadened, its width is dependent on the temperature structure of the atmosphere. In addition the n = 2 level population is controlled by the temperature-density structure of the atmosphere through excitation and ionization. Although the earlier work was based on a non-LTE approach for the transfer problem, the hydrogen ionization was not accounted for and the n = 2 level population was directly related to the total hydrogen density via the Boltzmann factor.


Optical Depth Line Source Profile Function Boltzmann Factor Radiative Transfer Calculation 
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  1. Cram, L. E. and Mullan, D. J., 1985, Astrophys. J., 294, 626.Google Scholar
  2. Drake, S. A., 1985, in Progress in Stellar Spectral Line Formation Theory, ed. J. E. Beckman and L. Crivellari, D. Reidel, p. 351.Google Scholar
  3. Dupree, A. K., 1986, Ann. Rev. Astron. Astrophys., 24, 377.Google Scholar
  4. Hartmann, L. and MacGregor, K. B., 1980, Astrophys. J. 242, 260.Google Scholar
  5. Mallik, S. V., 1982, J. Astrophys. Astron., 3, 39.Google Scholar
  6. Mallik, S. V., 1986, Mon. Not. R. Astron. Soc., 222, 307.Google Scholar
  7. Peraiah, A., 1980, Acta Astron., 30, 525.Google Scholar
  8. Peraiah, A., 1981, Astrophys. Space Sci., 77, 243.Google Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • Sushma V. Mallik
    • 1
  1. 1.Indian Institute of AstrophysicsBangaloreIndia

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