Kelt-17B: A Hot-Jupiter Transiting an A-Star in a misaligned orbit detected with Doppler Tomography

Abstract

We present the discovery of a hot Jupiter transiting the V = 9.23 mag main-sequence A-star KELT-17 (BD+14 1881). KELT-17b is a ${1.31}_{-0.29}^{+0.28}\,{M}_{{\rm{J}}}$, ${1.525}_{-0.060}^{+0.065}\,{R}_{{\rm{J}}}$ hot-Jupiter in a 3.08-day period orbit misaligned at −115fdg9 ± 4fdg1 to the rotation axis of the star. The planet is confirmed via both the detection of the radial velocity orbit, and the Doppler tomographic detection of the shadow of the planet during two transits. The nature of the spin–orbit misaligned transit geometry allows us to place a constraint on the level of differential rotation in the host star; we find that KELT-17 is consistent with both rigid-body rotation and solar differential rotation rates ($\alpha \lt 0.30$ at $2\sigma $ significance). KELT-17 is only the fourth A-star with a confirmed transiting planet, and with a mass of ${1.635}_{-0.061}^{+0.066}\,{M}_{\odot }$, an effective temperature of 7454 ± 49 K, and a projected rotational velocity of $v\sin {I}_{* }={44.2}_{-1.3}^{+1.5}\,\mathrm{km}\,{{\rm{s}}}^{-1};$ it is among the most massive, hottest, and most rapidly rotating of known planet hosts. Show more