  We use the super Earth 55 Cnc e as a case study to address an observable
effect of tidal heating. We investigate whether planet-planet interactions can
force the eccentricity of this planet to a level affecting the eclipse depth
observed with Spitzer. Using the constant time lag tidal model, we first
calculate the observed planet flux as a function of albedo and eccentricity,
for different tidal dissipation constants and for two extreme cases: a planet
with no heat redistribution and a planet with full heat redistribution. We
derive the values of albedo and eccentricity that match the observed transit
depth. We then perform N-body simulations of the planetary system including
tides and General Relativity to follow the evolution of the eccentricity of
planet e. We compare the range of eccentricities given by the simulations with
the eccentricities required to alter the eclipse depth. We find that the
eccentricity of planet e can be large enough to contribute at a measurable
level to the thermal emission measured with Spitzer. This affects the
constraints on the albedo of the planet, which can be as high as 0.9 (instead
of 0.55 when ignoring tidal heating). We also derive a maximum value for the
eccentricity of planet e directly from the eclipse depth: e<0.015 assuming
Earth's dissipation constant. Transiting exoplanets in multiple planet systems
are exceptional targets for testing tidal models because their tidal luminosity
may be observable. Future multi-wavelengths observations of eclipse depth and
phase curves (for instance with EChO and JWST) should allow us to better
resolve the temperature map of these planets and break the degeneracy between
albedo and tidal heating that remains for single band observations. In
addition, an accurate determination of the eccentricity will make it possible
to constrain the dissipation rate of the planet and to probe its internal
structure.
