  Transiting planets orbiting bright stars are the most favorable targets for
follow-up and characterization. We report the discovery of the transiting hot
Jupiter XO-7 b and of a second, massive companion on a wide orbit around a
circumpolar, bright, and metal rich G0 dwarf (V = 10.52, $T_{\rm eff} = 6250
\pm 100 \; \rm K$, $\rm[Fe/H] = 0.432 \pm 0.057 \; \rm dex$). We conducted
photometric and radial velocity follow-up with a team of amateur and
professional astronomers. XO-7 b has a period of $ 2.8641424 \pm 0.0000043$
days, a mass of $0.709 \pm 0.034 \; \rm M_{\rm J}$, a radius of $1.373 \pm
0.026 \; \rm R_{\rm J}$, a density of $0.340 \pm 0.027 \; \rm g \, {cm}^{-3}$,
and an equilibrium temperature of $1743 \pm 23 \; \rm K$. Its large atmospheric
scale height and the brightness of the host star make it well suited to
atmospheric characterization. The wide orbit companion is detected as a linear
trend in radial velocities with an amplitude of $\sim100 \; \rm m \, {s}^{-1}$
over two years, yielding a minimum mass of $4 \; \rm M_{\rm J}$; it could be a
planet, a brown dwarf, or a low mass star. The hot Jupiter orbital parameters
and the presence of the wide orbit companion point towards a high eccentricity
migration for the hot Jupiter. Overall, this system will be valuable to
understand the atmospheric properties and migration mechanisms of hot Jupiters
and will help constrain the formation and evolution models of gas giant
exoplanets.
