  We study thermal relaxation in a neutron star after internal heating events
(outbursts) in the crust. We consider thin and thick spherically symmetric
heaters, superfluid and non-superfluid crusts, stars with open and forbidden
direct Urca processes in their cores. In particular, we analyze long-term
thermal relaxation after deep crustal heating produced by nuclear
transformations in fully or partly accreted crusts of transiently accreting
neutron stars. This long-term relaxation has a typical relaxation time and an
overall finite duration time for the crust to thermally equilibrate with the
core. Neutron superfluidity in the inner crust greatly affects the relaxation
if the heater is located in the inner crust. It shortens and unifies the time
of emergence of thermal wave from the heater to the surface. This is important
for the interpretation of observed outbursts of magnetars and transiently
accreting neutron stars in quasi-persistent low-mass X-ray binaries.
