KELT-17b: A hot-Jupiter transiting an A-star in a misaligned orbit detected with Doppler tomography

TL;DR

This paper reports the discovery of a hot-Jupiter exoplanet transiting an A-star, KELT-17, with a highly misaligned orbit, confirmed through Doppler tomography and radial velocity measurements, providing insights into star-planet dynamics.

Contribution

The study presents the first Doppler tomographic detection of a transiting planet around an A-star with a highly misaligned orbit, expanding knowledge of planet-star interactions in massive, rapidly rotating stars.

Findings

KELT-17b is a 1.31 Mj, 1.525 Rj hot-Jupiter with a 3.08-day orbit.

The planet's orbit is misaligned at -115.9 degrees to the star's rotation axis.

KELT-17 is among the most massive, hottest, and fastest rotating stars known to host a transiting planet.

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 Mj, 1.525 -0.060/+0.065 Rj hot-Jupiter in a 3.08 day period orbit misaligned at -115.9 +/- 4.1 deg 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 over 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 < 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 Msun, effective temperature of 7454 +/- 49 K, and projected rotational velocity v sin I_* = 44.2 -1.3/+1.5 km/s; it is amongst the most massive, hottest, and most rapidly rotating of known planet hosts.