The winds of O-stars. III - A comparison between observed and predicted degrees of ionization in the winds of O-stars

Details The winds of O-stars. III - A comparison between observed and predicted degrees of ionization in the winds of O-stars The winds of O-stars. III - A comparison between observed and predicted degrees of ionization in the winds of O-stars

Mar 1991

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991a%26a...243..429g&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 243, no. 2, March 1991, p. 429-444.

Astronomy and Astrophysics

Astronomy

22

Gas Ionization, O Stars, Stellar Winds, Supergiant Stars, Ultraviolet Astronomy, Abundance, Main Sequence Stars, Stellar Temperature, Lines: Profile, Stars: Circumstellar Matter, Early Type, Mass-Loss, Uv Radiation

Scientific paper

The results of the UV line-fitting of 26 O-stars and one BO supergiant were used to compare the observed degrees of ionization in the winds with the predicted ionization for wind models calculated by Pauldrach (1987), Pauldrach et al. (1989) and Drew (1989). We have compared the empirical ionization structure in the entire wind for a few stars with the detailed models. For all our sample stars we compared empirical ionization ratios (e.g. N V/C IV, Si IV/C IV, N IV/N V) with their predicted values at υ = 0.5 υ∞.
Both comparisons led to the same conclusion as to the origin of the large discrepancies, up to factors 102 to 103, between predictions and observations.
In general both sets of theoretical calculations predict too much ionization. They underestimate the Si IV abundance and overestimate the C IV abundance at low effective temperatures. The N V abundance is overestimated for stars earlier than O7, but underestimated at O8 and later. The latter effect is the well known superionization. Both sets of theoretical calculations do not take Auger-ionization by X-rays into account which in principle might explain the presence of N V at low effective temperatures.

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