A. Lobel, J. Groh, K. Torres Dozinel, N. Gorlova, C. Martayan, G. Raskin, H. Van Winckel, S. Prins, W. Pessemier, C. Waelkens, Y. Frémat, H. Hensberge, L. Dummortier, A. Jorissen, S. Van Eck, H. Lehmann
Spectroscopic monitoring with Mercator-HERMES over the past two years reveals
that MWC 314 is a massive binary system composed of an early B-type primary LBV
star and a less-luminous supergiant companion. We determine an orbital period
Porb of 60.85 d from optical S II and Ne I absorption lines observed in this
single-lined spectroscopic binary. We find an orbital eccentricity of e=0.26,
and a large amplitude of the radial velocity curve of 80.6 km/s. The ASAS V
light-curve during our spectroscopic monitoring reveals two brightness minima
(\Delta V~0.1 mag.) over the orbital period due to partial eclipses at an
orbital inclination angle of ~70 degrees. We find a clear correlation between
the orbital phases and the detailed shapes of optical and near-IR P Cygni-type
line profiles of He I, Si II, and double- or triple-peaked stationary cores of
prominent Fe II emission lines. A preliminary 3-D radiative transfer model
computed with Wind3D shows that the periodic P Cygni line profile variability
results from an asymmetric common-envelope wind with enhanced density (or line
opacity) in the vicinity of the LBV primary. The variable orientation of the
inner LBV wind region due to the orbital motion produces variable P Cygni line
profiles (with wind velocities of ~200 km/s) between orbital phases \phi = 0.65
to 0.85, while weak inverse P Cygni profiles are observed half an orbital
period later around \phi = 0.15 to 0.35. We do not observe optical or near-IR
He II, C III, and Si III lines, signaling that the LBV's spectral type is later
than B0. Detailed modeling of the asymmetrical wind properties of massive
binary MWC 314 provides important new physical information about the most
luminous hot (binary) stars such as Eta Carinae.
View original:
http://arxiv.org/abs/1112.5994
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