Radiation from accelerated impurities in a Bose-Einstein condensate

We investigate radiation spectra arising from accelerated point-like impurities in the homogeneous Bose-Einstein condensate. A general formula for the radiation spectrum is obtained in the integral form as a function of given impurity trajectory within the Bogoliubov approximation. The Planckian spectrum is obtained for a special accelerated motion, which is shown to be unphysical. Non-Planckian spectrum is found in the case of a uniformly accelerated impurity. We compare our result with similar settings discussed in other quantum systems.