No GW is emitted by B PSR1913+16
  In the exact (non-linear) formulation of general relativity (GR) no motion of bodies can give origin to gravitational waves (GW's) - as it has been proved. Accordingly, the measured rate of change of the orbital period of binary pulsar B PSR1913+16 must have other causes, different from the emission of GW's; maybe the viscous losses of the unseen pulsar companion, if it were e.g. a helium star. 
A. Loinger (Dipartimento di Fisica, Universita' di Milano, Italy)