A Planet of an A-Star: HD15082b

TL;DR

This paper reports the discovery of a hot, transiting exoplanet orbiting a bright, rapidly rotating A5 star, with spectroscopic evidence of a retrograde orbit and an extremely high temperature, challenging detection methods.

Contribution

It presents the first spectroscopic detection of a transiting planet around a bright A-type star and details its retrograde orbit and high temperature.

Findings

The planet has a radius consistent with a gas giant.

It orbits in a retrograde direction relative to the star's rotation.

The planet's temperature is approximately 2700 K, making it one of the hottest known.

Abstract

Most of the known transiting extrasolar planets orbit slowly rotating F, G or K stars. In here we report on the detection of a transiting planet orbiting the bright, rapidly rotating A5 star HD15082 (WASP-33b, V=8.3, m sin i = 86 km s-1), recently made by SuperWASP. Time resolved spectroscopic observations taken during transit show a hump caused by the planet crossing the line profile. From the analysis of the spectra, we derive the radius of the planet and find that it is orbiting retrograde in respect to the spin of the star. Because of its small distance from an A5 star (the orbital period of only 1.22 days), the equilibrium temperature of the planet is estimated to be 2700 K. The planet thus is one of the hottest planets known, which makes it relatively easy to detect it in the IR. We thus tried to detect it using the TNG but did not succeed.