Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983apj...266..701k&link_type=abstract
Astrophysical Journal, Part 1, vol. 266, Mar. 15, 1983, p. 701-712.
Astronomy and Astrophysics
Astronomy
25
Late Stars, Radio Sources (Astronomy), Stellar Envelopes, Stellar Mass Ejection, Abundance, Cool Stars, Hydrogen Clouds, Radiation Distribution, Very Large Array (Vla)
Scientific paper
Chemically, the envelopes around evolved stars provide conditions which are different from those that are usually present in interstellar clouds. In many of these red giant stars atomic hydrogen is observed close to the star. However, neither atomic nor molecular hydrogen has ever been observed in the outer envelope. It is expected that the hydrogen in these envelopes is mostly molecular, but there are reasons to expect the presence of some fractional abundances of H I. The present investigation is concerned with an attempt to detect H I in circumstellar envelopes using the Very Large Array (VLA), taking into account 16 circumstellar envelopes. However, no evidence could be found for the existence of H I in any of the envelopes studied. The obtained results are in keeping with equilibrium calculations for cool stars, which suggest that the hydrogen in the photospheres of these stars is entirely in molecular form. For the hotter stars, however, a significant fraction of the hydrogen is expected to be in the form of H I.
Bowers Phillip F.
Knapp Gillan R.
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