Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1d&link_type=abstract
Ph.D. Thesis Calgary Univ. (Alberta). Dept. of Physics and Astronomy.
Astronomy and Astrophysics
Astronomy
3
B Stars, Infrared Astronomy, Infrared Photometry, Radio Astronomy, Radio Emission, Space Plasmas, Stellar Envelopes, Stellar Spectra, Color-Color Diagram, Emission Spectra, Extraterrestrial Radio Waves, Infrared Spectra, Near Infrared Radiation, Radio Spectra, Stellar Color, Variable Stars
Scientific paper
Circumstellar environments of Be stars are investigated via analysis of observations at near-infrared (IR) and radio wavelengths. Near-IR and quasi-simultaneous visual observations of Be and normal B-type stars were obtained. Intrinsic color relationships for B stars were derived. Excess IR emission is present for about 60% of Be stars. The excess color-color relationships are consistent with circumstellar envelopes of radius greater than 10 stellar radii and power law radial density distributions. The percentage of variable Be stars increases with wavelength, with 18% of the sample studied being identified as variables at K band. Variations are attributed to density variations in the circumstellar plasma. New multi-wavelength radio observations of six Be stars are presented, three of which appear to have variable radio emission. Emission from the Be star Psi Persei is resolved at 15 GHz. The radio emitting region has a major axis dimension of 111 milli arc seconds (mas) and the minor axis has an upper limit of 68 mas. The angular size of the major axis corresponds to a radius of 1,850 solar radii (SR). Using a radiative transfer disc model, it is shown that a truncated circumstellar disc cannot account for both the IR to radio spectrum of the excess emission and the observed radius of 1,850 SR.
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