Spectroscopic orbits and variations of RS Oph
  The aims of our study are to improve the orbital elements of the giant and to
derive the spectroscopic orbit for the white dwarf companion. Spectral
variations related to the 2006 outburst are also studied. The spectroscopic
orbits have been obtained by measuring the radial velocities of the cool
component absorption lines and the broad Halpha emission wings, which seem to
be associated with the hot component. A set of cF-type absorption lines were
also analyzed for a possible connection with the hot component motion. A new
period of 453.6 days and a mass ratio, q=M_g/M_h=0.59 were determined. Assuming
a massive white dwarf as the hot component, M_h= 1.2-1.4 M_{\odot}, the red
giant mass is M_g= 0.68-0.80 M_{\odot} and the orbit inclination, i =
49-52^{\circ}. The cF-type lines are not associated with either binary
component, and are most likely formed in the material streaming towards the hot
component. We also confirm the presence of the LiI doublet in RS Oph and its
radial velocities fit very well the M-giant radial velocity curve. Regardless
of the mechanism involved to produce lithium, its origin is most likely from
within the cool giant rather than material captured by the giant at the time of
the nova explosion. In April 2006 most of the emission lines present a broad
pedestal with a strong and narrow component at about -20 km/s and two other
extended emission components at -200 and +150 km/s. These components could
originate in a bipolar gas outflow supporting the model of a bipolar
shock-heated shell expanding through the cool component wind perpendicularly to
the binary orbital plane.
