  In some situations in stochastic thermodynamics not all relevant slow degrees
of freedom are accessible. Consequently, one adopts an effective description
involving only the visible degrees of freedom. This gives rise to an apparent
entropy production that violates standard fluctuation theorems. We present an
analytically solvable model illustrating how the fluctuation theorems are
modified. Furthermore, we define an alternative to the apparent entropy
production: the marginal entropy production which fulfills the fluctuation
theorems in the usual form. We show that the non-Markovianity of the visible
process is responsible for the deviations in the fluctuation theorems.
