  We study numerically the dynamics of the Rabi Hamiltonian, describing the
interaction of a single cavity mode and a two-level atom without the rotating
wave approximation, subjected to damping and dephasing reservoirs included via
usual Lindblad superoperators in the master equation. We show that the
combination of the antirotating term and the atomic dephasing leads to linear
asymptotic photons generation from vacuum. We reveal the origins of the
phenomenon and estimate its importance in realistic situations.
