Context : M dwarfs have been found to often have super-Earth planets with short orbital periods .
Such stars are thus preferential targets in searches for rocky or ocean planets in the solar neighbourhood .

Aims : In a recent paper ( Bonfils et al .
2011 ) , we announced the discovery of respectively 1 and 2 low mass planets around the M1.5V stars Gl 433 and Gl 667C .
We found those planets with the HARPS spectrograph on the ESO 3.6-m telescope at La Silla Observatory , from observations obtained during the Guaranteed Time Observing program of that instrument .

Methods : We have obtained additional HARPS observations of those two stars , for a total of respectively 67 and 179 Radial Velocity measurements for Gl 433 and Gl 667C , and present here an orbital analysis of those extended data sets and our main conclusion about both planetary systems .

Results : One of the three planets , Gl 667Cc , has a mass of only M _ { 2 } . \sin { i } \sim 4.25 ~ { } M _ { \oplus } and orbits in the central habitable zone of its host star .
It receives just 10 % less stellar energy from Gl 667C than the Earth receives from the Sun .
However planet evolution in habitable zone can be very different if the host star is a M dwarf or a solar-like star , without necessarily questioning the presence of water .
The two other planets , Gl 433b and Gl 667Cb , both have M _ { 2 } . \sin { i } of \sim 5.5 M _ { \oplus } and periods of \sim 7 days .
The Radial Velocity measurements of both stars contain longer time scale signals , which we fit as longer period Keplerians .
For Gl 433 that signal probably originates in a Magnetic Cycle , while a longer time span will be needed to conclude for Gl 667C .
The metallicity of Gl 433 is close to solar , while Gl 667C is metal poor with [ Fe/H ] \sim -0.6 .
This reinforces the recent conclusion that the occurence of Super-Earth planets does not strongly correlate with stellar metallicity .

Conclusions :