The quasar PG 1302 - 102 is believed to harbour a supermassive binary black hole ( SMBBH ) system .
Using the available 15 GHz and 2 - 8 GHz , multi-epoch Very Long Baseline Array data , we constrain the pc-scale jet properties based on the inferred mean proper motion , including a bulk Lorentz factor \geqslant 5.1 \pm 0.8 , jet inclination angle \leqslant 11 \fdg 4 \pm 1 \fdg 7 , projected position angle = 31 \fdg 8 , intrinsic half opening angle \leqslant 0 \fdg 9 \pm 0 \fdg 1 and a mean 2 - 8 GHz spectral index of 0.31 .
A general relativistic helical jet model is presented and applied to predict quasi-periodic oscillations of \sim 10 days , power law power spectrum shape and a contribution of up to \sim 53 percent to the observed variable core flux density .
The model is used to make a case for high resolution , moderately sampled , long duration radio interferometric observations to reveal signatures due to helical knots and distinguish them from those due to SMBBH orbital activity including a phase difference \sim \pi and an amplitude ratio ( helical light curve amplitude/SMBBH light curve amplitude ) of 0.2 - 3.3 .
The prescription can be used to identify helical kinematic signatures from quasars , providing possible candidates for further studies with polarization measurements .
It can also be used to infer promising SMBBH candidates for the study of gravitational waves if there are systematic deviations from helical signatures .