N. Blind, H. M. J. Boffin, J. -P. Berger, J. -B. Le Bouquin, A. Mérand, B. Lazareff, G. Zins
Context. Determining the mass transfer in a close binary system is of prime
importance for understanding its evolution. SS Leporis, a symbiotic star
showing the Algol paradox and presenting clear evidence of ongoing mass
transfer, in which the donor has been thought to fill its Roche lobe, is a
target particularly suited to this kind of study. Aims. Since previous
spectroscopic and interferometric observations have not been able to fully
constrain the system morphology and characteristics, we go one step further to
determine its orbital parameters, for which we need new interferometric
observations directly probing the inner parts of the system with a much higher
number of spatial frequencies. Methods. We use data obtained at eight different
epochs with the VLTI instruments AMBER and PIONIER in the H- and K-bands. We
performed aperture synthesis imaging to obtain the first model-independent view
of this system. We then modelled it as a binary (whose giant is spatially
resolved) that is surrounded by a circumbinary disc. Results. Combining these
interferometric measurements with previous radial velocities, we fully
constrain the orbit of the system. We then determine the mass of each star and
significantly revise the mass ratio. The M giant also appears to be almost
twice smaller than previously thought. Additionally, the low spectral
resolution of the data allows the flux of both stars and of the dusty disc to
be determined along the H and K bands, and thereby extracting their
temperatures. Conclusions. We find that the M giant actually does not stricto
sensus fill its Roche lobe. The mass transfer is more likely to occur through
the accretion of an important part of the giant wind. We finally rise the
possibility for an enhanced mass loss from the giant, and we show that an
accretion disc should have formed around the A star.
View original:
http://arxiv.org/abs/1112.1514
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