  We present stellar wind modelling of the hot Jupiter host HD189733, and
predict radio emission from the stellar wind and the planet, the latter arising
from the interaction of the stellar wind with the planetary magnetosphere. Our
stellar wind models incorporate surface stellar magnetic field maps at the
epochs Jun/Jul 2013, Sep 2014, and Jul 2015 as boundary conditions. We find
that the mass-loss rate, angular momentum-loss rate, and open magnetic flux of
HD189733 vary by 9%, 40%, and 19% over these three epochs. Solving the
equations of radiative transfer, we find that from 10 MHz-100 GHz the stellar
wind emits fluxes in the range of $10^{-3}$-$5$ $\mu$Jy, and becomes optically
thin above 10 GHz. Our planetary radio emission model uses the radiometric
Bode's law, and neglects the presence of a planetary atmosphere. For assumed
planetary magnetic fields of 1-10 G, we estimate that the planet emits at
frequencies of 2-25 MHz, with peak flux densities of $\sim10^2$ mJy. We find
that the planet orbits through regions of the stellar wind that are optically
thick to the emitted frequency from the planet. As a result, unattenuated
planetary radio emission can only propagate out of the system and reach the
observer for 67% of the orbit for a 10 G planetary field, corresponding to when
the planet is approaching and leaving primary transit. We also find that the
plasma frequency of the stellar wind is too high to allow propagation of the
planetary radio emission below 21 MHz. This means a planetary field of at least
8 G is required to produce detectable radio emission.
