Isomonodromy sets of accessory parameters for Heun class equations

In this paper, we consider the monodromy and, in particular, isomonodromy sets of accessory parameters for Heun class equations. We show that equations can be obtained as limits linear systems associated with Painlevé when transcendents go to one actual singular points systems. The are described by Taylor or Laurent coefficients corresponding functions, tau at positions critical values. As an application these results, derive some asymptotic approximations equations, including confluent equation, doubly-confluent and reduced biconfluent equation.