We present new high angular resolution interferometer observations of the v = 0 J = 14 - 13 and 15 - 14 SiS lines towards IRC+10216 , carried out with CARMA and ALMA .
The maps , with angular resolutions of \simeq 0 \farcs 25 and 0 \farcs 55 , reveal ( 1 ) an extended , roughly uniform , and weak emission with a size of \simeq 0 \farcs 5 , ( 2 ) a component elongated approximately along the East-West direction peaking at \simeq 0 \farcs 13 and 0 \farcs 17 at both sides of the central star , and ( 3 ) two blue- and red-shifted compact components peaking around 0 \farcs 07 to the NW of the star .
We have modeled the emission with a 3D radiation transfer code finding that the observations can not be explained only by thermal emission .
Several maser clumps and one arc-shaped maser feature arranged from 5 to 20 R _ { \star } from the central star , in addition to a thin shell-like maser structure at \simeq 13 R _ { \star } are required to explain the observations .
This maser emitting set of structures accounts for 75 % of the total emission while the other 25 % is produced by thermally excited molecules .
About 60 % of the maser emission comes from the extended emission and the rest from the set of clumps and the arc .
The analysis of a time monitoring of these and other SiS and ^ { 29 } SiS lines carried out with the IRAM 30 m telescope from 2015 to present suggests that the intensity of some spectral components of the maser emission strongly depends on the stellar pulsation while other components show a mild variability .
This monitoring evidences a significant phase lag of \simeq 0.2 between the maser and NIR light-curves .