TOI-1431b/MASCARA-5b: An Ultra-hot Jupiter Orbiting One of the Hottest & Brightest Known Exoplanet Host Stars

Here I present the discovery of an ultra-hot Jupiter, TOI-1431b/MASCARA-5b, detected by TESS and MASCARA. Radial velocity measurements with SONG, SOPHIE, FIES, NRES, and EXPRES confirms the planet candidate with a reflex motion of K=294.1±1.1m/s. A joint analysis of the photometry and RVs gives TOI-1431b a mass of M_p=3.14±0.19M_J, an inflated radius of R_p=1.51±0.06R_J (16.9±0.7R_e), and an orbital period of P~2.65d. The planet orbits a bright (V=8.05mag), young (~290Myr), and hot (T_eff~7700K) Am type star. Using TESS photometry, we were able to measure the planet's thermal emissions in the red-optical from the full phase curve and secondary eclipse, allowing us to determine the dayside and nightside temperature of its atmosphere as T_day=2983±68K and T_night=2556±65K. The planet's low day/night temperature contrast (~400K) suggests very efficient heat transport between the dayside and nightside hemispheres. Given the host star brightness, the planet is ideal for intensive atmospheric characterization through transmission and emission spectroscopy from space missions such as JWST and ARIEL.