Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991a%26a...241..159m&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 241, no. 1, Jan. 1991, p. 159-166. Research supported by Fondo Nacional de Cie
Astronomy and Astrophysics
Astrophysics
15
B Stars, Emission Spectra, H Beta Line, Line Shape, Spectrum Analysis, Variable Stars, Stellar Atmospheres, Stellar Envelopes, Stellar Oscillations, Stellar Spectra, Be Stars, Spectroscopy, Emission Lines
Scientific paper
The V/R ratio between the violet and red intensity peaks of the Hβ emission line of 33 southern Be stars was examined, covering periods from several years to several decades. 76% of our sample stars were found to be V/R variables. Long- term variables are characterized by quasiperiods mainly in the 2-13 years range with a mean T= 7 yr. Six short-term variables were found which are best characterized by V> R to V< R changes on time-scales of 6-100 d. A statistical analysis of these data, including also data for 10 northern V/R variables, did not reveal any correlation of the quasiperiod T with the spectral type and projected rotational velocity (υ sin i) of the central star. Long- term quasiperiods do not depend on the envelope size. However, only stars with small envelopes (rβ ≲ 4r*) show short-term variations. We discuss several possible mechanisms for these variations and have concluded that the most satisfactory general interpretation for the long-term variations seems to be expansion and contraction of the envelope, triggered by a variable stellar wind. On the other hand, the short-term V/R variations could be caused by the rotation of inhomogeneities in the circumstellar envelope (blobs), possibly combined with atmospheric phenomena in the central star such as non-radial pulsations and/or anisotropic radiation fields.
Mennickent Ronald E.
Vogt Nicolas
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