  Doppler CORALIE measurements of the solar-type stars HD141937, HD162020,
HD168443 and HD202206 show Keplerian radial-velocity variations revealing the
presence of 4 new companions with minimum masses close to the
planet/brown-dwarf transition, namely with m_2sin(i) = 9.7, 14.4, 16.9, and
17.5 M_Jup, respectively. The orbits present fairly large eccentricities
(0.22<e<0.43). Except for HD162020, the parent stars are metal rich compared to
the Sun, as are most of the detected extra-solar planet hosts. Considerations
of tidal dissipation in the short-period HD162020 system points towards a
brown-dwarf nature for the low-mass companion. HD168443 is a multiple system
with two low-mass companions being either brown dwarfs or formed simultaneously
in the protoplanetary disks as superplanets. For HD202206, the radial
velocities show an additional drift revealing a further outer companion, the
nature of which is still unknown. Finally, the stellar-host and orbital
properties of massive planets are examined in comparison to lighter exoplanets.
Observed trends include the need of metal-rich stars to form massive exoplanets
and the lack of short periods for massive planets. If confirmed with improved
statistics, these features may provide constraints for the migration scenario.

Astrophysics