  We report on new transit photometry for the super-Earth 55 Cnc e obtained
with Warm Spitzer/IRAC at 4.5 microns. An individual analysis of these new data
leads to a planet radius of 2.21-0.16+0.15 Rearth, in good agreement with the
values previously derived from the MOST and Spitzer transit discovery data. A
global analysis of both Spitzer transit time-series improves the precision on
the radius of the planet at 4.5 microns to 2.20+-0.12 Rearth. We also performed
an independent analysis of the MOST data, paying particular attention to the
influence of the systematic effects of instrumental origin on the derived
parameters and errors by including them in a global model instead of performing
a preliminary detrending-filtering processing. We deduce an optical planet
radius of 2.04+0.15 Rearth from this reanalysis of MOST data, which is
consistent with the previous MOST result and with our Spitzer infrared radius.
Assuming the achromaticity of the transit depth, we performed a global analysis
combining Spitzer and MOST data that results in a planet radius of 2.17+-0.10
Rearth (13,820+-620 km). These results point to 55 Cnc e having a gaseous
envelope overlying a rocky nucleus, in agreement with previous works. A
plausible composition for the envelope is water which would be in
super-critical form given the equilibrium temperature of the planet.
