WASP-189b: an ultra-hot Jupiter transiting the bright A star HR 5599 in a polar orbit

Abstract

We report the discovery of WASP-189b: an ultra-hot Jupiter in a 2.72-d transiting orbit around the $V=6.6$ A star WASP-189 (HR 5599). We detected periodic dimmings in the star's lightcurve, first with the WASP-South survey facility then with the TRAPPIST-South telescope. We confirmed that a planet is the cause of those dimmings via line-profile tomography and radial-velocity measurements using the HARPS and CORALIE spectrographs. Those reveal WASP-189b to be an ultra-hot Jupiter ($M_{\mathrm{P}}$ = 2.13 $\pm$ 0.28 $M_{\mathrm{Jup}}$; $R_{\mathrm{P}}$ = 1.374 $\pm$ 0.082 $R_{\mathrm{Jup}}$) in a polar orbit ($\hat{I}»=89.3\pm 1.4^{\circ }$; $\hat{I}¨=90.0\pm 5.8^{\circ }$) around a rapidly rotating A6IV-V star ($T_{\mathrm{eff}}$ = 8000 $\pm$ 100 K; $v_{\ast }\sin i_{\ast }$ $\approx$ 100 km\, s${}^{-1}$). We calculate a predicted equilibrium temperature of $T_{\mathrm{eql}}$ = 2641 $\pm$ 34 K, assuming zero albedo and efficient redistribution, which is the third hottest for the known exoplanets. WASP-189 is the brightest known host of a transiting hot Jupiter and the third-brightest known host of any transiting exoplanet. We note that of the eight hot-Jupiter systems with $T_{\mathrm{eff}}$ $>$ 7000 K, seven have strongly misaligned orbits, and two of the three systems with $T_{\mathrm{eff}}$ $\ge$ 8000 K have polar orbits (the third is aligned).

Submitted to MNRAS. 10 pages, 9 figures, 3 tables