WASP-South hot Jupiters: WASP-178b, WASP-184b, WASP-185b, and WASP-192b

We report on four new transiting hot Jupiters discovered by the WASP-South survey. WASP-178b transits a V = 9.9, A1V star with T_eff = 9350 ± 150 K, the second-hottest transit host known. It has a highly bloated radius of 1.81 ± 0.09 R_Jup, in line with the known correlation between high irradiation and large size. With an estimated temperature of 2470 ± 60 K, the planet is one of the best targets for studying ultrahot Jupiters that is visible from the Southern hemisphere. The three host stars WASP-184, WASP-185, and WASP-192 are all post-main-sequence G0 stars of ages 4-8 Gyr. The larger stellar radii (1.3-1.7 M_⊙) mean that the transits are relatively shallow (0.7-0.9 per cent) even though the planets have moderately inflated radii of 1.2-1.3 R_Jup. WASP-185b has an eccentric orbit (e = 0.24) and a relatively long orbital period of 9.4 d. A star that is 4.6 arcsec from WASP-185 and 4.4 mag fainter might be physically associated.