  We consider a 1D mechanical system $$\bar {\mathtt H}(\mathtt P,\mathtt
Q)=\mathtt P^2+\bar {\mathtt G}(\mathtt Q)$$ in action-angle variable $(\mathtt
P,\mathtt Q)$ where $\bar {\mathtt G}$ is a $2\pi$-periodic analytic function
with non degenerate critical points. Then, we consider a small analytic
perturbation of $\bar {\mathtt H}$ of the form $${\mathtt H}^*(\mathtt
P,\mathtt Q;\hat{\mathtt P}) = \mathtt P^2+\bar {\mathtt G}(\mathtt Q)+ \eta
{\mathtt F} (\mathtt P,\mathtt Q;\hat{\mathtt P})=:\mathtt P^2 + {\mathtt
G}^*(\mathtt P,\mathtt Q;\hat{\mathtt P})\,, \qquad \eta\ll 1\ ,$$ where the
perturbed potential $ {\mathtt G}^*$ may depend on the action $\mathtt P$ and
also on parameters $\hat{\mathtt P}$ ("the adiabatic actions"); indeed, this is
the form of a finite dimensional mechanical system close to an exact simple
resonance after averaging over fast angles and disregarding the exponentially
small remainder, see [5]. Up to a finite number of separatrices and
elliptic/hyperbolic points the phase space of ${\mathtt H}^*$ is divided into a
finite number of open connected components foliated by invariant circles. On
every connected component we perform a (Arnold-Liouville) symplectic
action-angle transformation which integrates the system. We give a complete and
quantitative description of the analyticity properties of such integrating
transformations, estimating, in particular, how such transformations differ
from the integrating transformation for $\bar {\mathtt H}$; compare Theorem 6.1
below.
