Consequences of a chromospheric temperature rise on the formation of the H-alpha line in late-type supergiants

Abstract

Computations of the H-alpha line profiles were performed in a non-LTE moving chromosphere with temperature rise to simulate the observed H-alpha characteristics in G and K supergiants. The comoving frame radiative transfer code was modified to incorporate explicitly the effects of hydrogen ionization. The sensitivity of H-alpha profiles to a variety of temperature structures, velocity gradients, and chromospheric extents and densities is examined and illustrated. Comparison of the observed profiles to computed ones gives total hydrogen densities in the range between 10 to the 9th and 10 to the 11th/cu cm at the base of the line forming region. Integrated chromospheric optical depths in the range of 50-5000 and expansion velocities in the range of 0.25-2 times the maximum random (microturbent and thermal) velocity are found. The mass loss rate is inferred to be in the range between 10 to the -7th and 10 to the -9th solar masses/year.