  We present a study of hybrid neutron stars with color superconducting quark
matter cores at finite temperature that results in sequences of stars with
constant entropy per baryon, $s/n_B={\rm const}$. For the quark matter equation
of state, we employ a recently developed nonlocal chiral quark model while
nuclear matter is described with a relativistic density functional model of the
DD2 class. The phase transition is obtained by a Maxwell construction under
isothermal conditions. We find that traversing the mixed phase on a trajectory
at low $s/n_B\lesssim 2$ in the phase diagram shows a heating effect while at
larger $s/n_B$ the temperature drops. This behavior may be attributed to the
presence of a color superconducting quark matter phase at low temperatures and
the melting of the diquark condensate which restores the normal quark matter
phase at higher temperatures. While the isentropic hybrid star branch at low
$s/n_B\lesssim 2$ is connected to the neutron star branch, it gets disconnected
at higher entropy per baryon so that the "thermal twin" phenomenon is observed.
We find that the transition from connected to disconnected hybrid star
sequences may be estimated with the Seidov criterion for the difference in
energy densities. The radii and masses at the onset of deconfinement exhibit a
linear relationship and thus define a critical compactness of the isentropic
star configuration for which the transition occurs which for large enough
$s/n_B\gtrsim 2$ is accompanied by an instability. The results of this study
may be of relevance for uncovering the conditions for the supernova
explodability of massive blue supergiant stars by the quark deconfinement
mechanism. The accretion-induced deconfinement transition with thermal twin
formation may contribute to explaining the origin of eccentric orbits in some
binary systems and the origin of isolated millisecond pulsars.
