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The polarization of Hβ in γ Cas

Published online by Cambridge University Press:  26 May 2016

Y.M. Jiang
Affiliation:
Department of Geophysics and Astronomy, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
G.A.H. Walker
Affiliation:
Department of Geophysics and Astronomy, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
N. Dinshaw
Affiliation:
Department of Geophysics and Astronomy, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
J.M. Matthews
Affiliation:
Department of Geophysics and Astronomy, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada

Extract

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High resolution (0.15 Å/pixel) spectropolarimetry across the Hβ emission line of the Be star γ Cas is presented (solid line in Figure B), as well as the intensity profile (Figure A). Earlier observations of the linear polarization across the emission lines (PL) in Be stars (Coyne 1975, Poeckert 1975) found that PL is inversely proportional to the total intensity of the emission line. However, our data clearly show that the width of the polarization profile is much wider than that of the emission line. The dotted line in Figure B gives PL, based on the relationship of: which follows directly from Coyne (1975), where IA is the intensity of the underlying Hβ absorption feature, Itotal the observed intensity profile, and PC the polarization in the adjacent continuum. The underlying stellar profile of Hβ (dotted line in Figure C), adopted from models by Hubeny (1988), gives a good match to the wings of the depolarization profile.

Type
4. Polarization
Copyright
Copyright © Kluwer 1994 

References

Coyne, G.V.: 1975, I.A.U. Symp. 70, Be and shell stars, 233 Google Scholar
Hubeny, I.: 1988, Computer Physics Communications 52, 103 Google Scholar
Poeckert, R.: 1975, Astrophysical Journal 196, 777 Google Scholar
Poeckert, R. and Marlborough, J.M.: 1978, Astrophysical Journal 220, 940 Google Scholar