This paper presents a consistent description of the formation and the subsequent evolution of gaseous planets , with special attention to short-period , low-mass hot-Neptune planets characteristic of \mu Ara-like systems .
We show that core accretion including migration and disk evolution and subsequent evolution taking into account irradiation and evaporation provide a viable formation mechanism for this type of strongly irradiated light planets .
At an orbital distance a \simeq 0.1 AU , this revised core accretion model leads to the formation of planets with total masses ranging from \sim 14 { M } _ { \oplus } ( 0.044 M _ { J } ) to \sim 400 { M } _ { \oplus } ( 1.25 M _ { J } ) .
The newly born planets have a dense core of \sim 6 { M } _ { \oplus } , independent of the total mass , and heavy element enrichments in the envelope , M _ { Z,env } / M _ { env } , varying from 10 % to 80 % from the largest to the smallest planets .
We examine the dependence of the evolution of the born planet on the evaporation rate due to the incident XUV stellar flux .
In order to reach a \mu Ara-like mass ( \sim 14 { M } _ { \oplus } ) after \sim 1 Gyr , the initial planet mass must range from 166 { M } _ { \oplus } ( \sim 0.52 M _ { J } ) to about 20 { M } _ { \oplus } , for evaporation rates varying by 2 orders of magnitude , corresponding to 90 % to 20 % mass loss during evolution .
The presence of a core and heavy elements in the envelope affects appreciably the structure and the evolution of the planet and yields \sim 8 \% - 9 \% difference in radius compared to coreless objects of solar composition for Saturn-mass planets .
These combinations of evaporation rates and internal compositions translate into different detection probabilities , and thus different statistical distributions for hot-Neptunes and hot-Jupiters .
These calculations provide an observable diagnostic , namely a mass-radius-age relationship to distinguish between the present core-accretion-evaporation model and the alternative colliding core scenario for the formation of hot-Neptunes .