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Título del libro: B(e) Phenomenon: Forty Years Of Studies
Título del capítulo: Short-Term Spectral Variability in the Binary FS CMa-Type Object MWC 728

Autores UNAM:
SERGUEI JARIKOV;
Autores externos:

Idioma:

Año de publicación:
2017
Palabras clave:

GALACTIC FSCMA STARS; PHOTOMETRY


Resumen:

We report the results of a long-term spectroscopic monitoring of the FS CM-type object MWC 728. We found that it is a binary system with a B5 ve (T-1,(eff) = 14000 +/- 1000 K) primary and a G8 III (T-2,(eff) similar to 5000 K) secondary. Absorption lines of the cool star show regular variations with a semi-amplitude of similar to 20 km s(-1) and a period of 27.5 days. The system mass function is 2.3x10(-2) M-circle dot, and its orbital plane is similar to 13 - 15 degrees tilted from the plane of the sky. The hot star has a projected rotational velocity of similar to 110 km s(-1) which implies a nearly breakup rotation at the equator. We detected strong variations of the Balmer and Her emission-line profiles on timescales from days to years. This points out to a variable stellar wind of the hot star in addition to the presence of a circum-primary gaseous disk. The strength of the absorption-line spectrum along with the optical and near-IR continuum suggest that the hot star contributes similar to 60% of the V-band flux, the disk contributes similar to 30%, and the cool star similar to 10%. The binary system parameters, along with the interstellar extinction, suggest a distance of similar to 1 kpc, that the cool star radius (similar to 8 R-circle dot) is smaller than its Roche lobe, and that the companions' mass ratio is q similar to 0.5. Overall, the observed spectral variability and the presence of a strong IR-excess are in agreement with a model of a close binary system that has undergone a non-conservative mass-transfer.


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