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Title:
A double shock wave atmospheric model for the Beta Cephei star Sigma Scorpii?
Authors:
Mathias, P.; Gillet, D.; Crowe, R.
Affiliation:
AA(Haute-Provence, Observatoire, Saint-Michel-l'Observatoire, France), AB(Haute-Provence, Observatoire, Saint-Michel-l'Observatoire, France), AC(Hawaii, University, Hilo)
Publication:
Astronomy and Astrophysics (ISSN 0004-6361), vol. 252, no. 1, Dec. 1991, p. 245-254. (A&A Homepage)
Publication Date:
12/1991
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
ATMOSPHERIC MODELS, CEPHEID VARIABLES, SHOCK WAVES, STELLAR SPECTROPHOTOMETRY, H ALPHA LINE, HIGH RESOLUTION, SIGNAL TO NOISE RATIOS, SPECTRAL RESOLUTION
Bibliographic Code:
1991A&A...252..245M

Abstract

This study presents high spectral and time-resolution observations of high signal-to-noise ratio (above 200), carried out at H-alpha and the Si III 4554, 4567 lines of the Beta Cephei star Sigma Sco. On a few spectra, the line of the 330-d companion is visible for the first time. Heliocentric radial velocity curves are determined which show a nice stillstand between two discontinuities. These discontinuities are interpreted as being due to the propagation of two shock waves, separated by about 1 h 30 min. The first and main shock is confirmed by a clearly visible line doubling phenomenon which is predicted by the mechanism of Schwarzschild (1952). These waves produce an acceleration ratio of 4:1 for S III and 6:1 for H-alpha, implying a weaker second shock wave compared to the first one. This is also indicated by the presence of a stronger Van Hoof effect at the second acceleration phase, which is interpreted as being due to the propagation time of the wave through the atmosphere.

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