MASCARA-1 b: A hot Jupiter transiting a bright $m_V=8.3$ A-star in a misaligned orbit

We report the discovery of MASCARA-1 b, the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). It is a hot Jupiter orbiting a bright $m_V=8.3$, rapidly rotating ($v\sin i_{\star }>100{\mathrm{k}\mathrm{m}\mathrm{s}}^{-1}$) A8 star with a period of $2.148780\pm 8\times {10}^{-6}\mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$. The planet has a mass and radius of $3.7\pm 0.9{\mathrm{M}}_{\mathrm{J}\mathrm{u}\mathrm{p}}$ and $1.5\pm 0.3{\mathrm{R}}_{\mathrm{J}\mathrm{u}\mathrm{p}}$, respectively. As with most hot Jupiters transiting early-type stars we find a misalignment between the planet orbital axis and the stellar spin axis, which may be signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of $1.5\pm 0.9\mathrm{g}\mathrm{c}{\mathrm{m}}^{-3}$ and an equilibrium temperature of $2570_{-30}^{+50}\mathrm{K}$, one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA.