MASCARA-2 b: A hot Jupiter transiting the $m_V=7.6$ A-star HD185603

Abstract

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 $3.474119_{-0.000006}^{+0.000005}\mathrm{days}$ at a distance of $0.057\pm 0.006\mathrm{AU}$, has a radius of $1.83\pm 0.07{\mathrm{R}}_{\mathrm{J}}$ and place a $99\%$ upper limit on the mass of $<17{\mathrm{M}}_{\mathrm{J}}$. HD 185603 is a rapidly rotating early-type star with an effective temperature of $8980_{-130}^{+90}\mathrm{K}$ and a mass and radius of $1.89_{-0.05}^{+0.06}{M}_{\odot }$, $1.60\pm 0.06R_{\odot }$, 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 $\hat{I}»=0.6\pm 4^{\circ }$. The brightness of the host star and the high equilibrium temperature, $2260\pm 50\mathrm{K}$, 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.

8 pages, 4 figures, Accepted for publication in A&A