  We analyze the heat exchange distribution of quantum open systems undergoing
a thermal relaxation that maximizes the entropy production. We show that the
process implies a type of generalized law of cooling in terms of a time
dependent effective temperature $T_t$. Using a two-point measurement scheme, we
find an expression for the heat moment generating function that depends solely
on the system's partition function and on the law of cooling. Applications
include the relaxation of free bosonic and fermionic modes, for which closed
form expressions for the time-dependent heat distribution function are derived.
Multiple free modes with arbitrary dispersion relations are also briefly
discussed. In the semiclassical limit our formula agrees well with previous
results of the literature for the heat distribution of an optically trapped
nanoscopic particle far from equilibrium.
