2018A&A...612A..57T

In this paper we present MASCARA-2 b, a hot Jupiter transiting the mV=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 3000h 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_–0.000006days at a distance of 0.057±0.006au, has a radius of 1.83±0.07R_J and place a 99% upper limit on the mass of <17M_J. HD 185603 is a rapidly rotating early-type star with an effective temperature of 8980⁺⁹⁰_–130K and a mass and radius of 1.89^+0.06_–0.05M☉, 1.60±0.06R☉, 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 λ=0.6±4°. The brightness of the host star and the high equilibrium temperature, 2260±50K, 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.