In this paper we present MASCARA-2 b, a hot Jupiter transiting the $m_V=7.6$ A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million flux measurements of the star, corresponding to a total of almost 3000 hours of observations, revealing a periodic dimming in the flux with a depth of $1.3%$. Photometric follow-up observations were performed with the NITES and IAC80 telescopes and spectroscopic measurements were obtained with the Hertzsprung SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of $3.474119^{+0.000005}_{-0.000006}~rm{days}$ at a distance of $0.057 pm 0.006~rm{AU}$, has a radius of $1.83 pm 0.07~rm{R}_{rm{J}}$ and place a $99%$ upper limit on the mass of $< 17~rm{M}_{rm{J}}$. HD 185603 is a rapidly rotating early-type star with an effective temperature of $8980^{+90}_{-130}~rm{K}$ and a mass and radius of $1.89^{+0.06}_{-0.05}~M_odot$, $1.60 pm 0.06~R_odot$, respectively. Contrary to most other hot Jupiters transiting early-type stars, the projected planet orbital axis and stellar spin axis are found to be aligned with $lambda=0.6 pm 4^circ$. The brightness of the host star and the high equilibrium temperature, $2260 pm 50~rm{K}$, of MASCARA-2 b make it a suitable target for atmospheric studies from the ground and space. Of particular interest is the detection of TiO, which has recently been detected in the similarly hot planets WASP-33 b and WASP-19 b.
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