TOI-1431b/MASCARA-5b: A Highly Irradiated Ultra-Hot Jupiter Orbiting One of the Hottest & Brightest Known Exoplanet Host Stars

Kavli Affiliate: Alan M. Levine

| First 5 Authors: Brett Christopher Addison, Emil Knudstrup, Ian Wong, Guillaume Hebrard, Patrick Dorval

| Summary:

We present the discovery of a highly irradiated and moderately inflated
ultra-hot Jupiter, TOI-1431b/MASCARA-5b (HD 201033b), first detected by NASA’s
Transiting Exoplanet Survey Satellite mission (TESS) and the Multi-site All-Sky
CAmeRA (MASCARA). The signal was established to be of planetary origin through
radial velocity measurements obtained using SONG, SOPHIE, FIES, NRES, and
EXPRES, which show a reflex motion of $K=294.1pm1.1$ m s$^{-1}$. A joint
analysis of the TESS and ground-based photometry and radial velocity
measurements reveals that TOI-1431b has a mass of $M_{p}=3.12pm0.18$
$rm{M_J}$ ($990pm60$ M$_{oplus}$), an inflated radius of $R_{p}=1.49pm0.05$
$rm{R_J}$ ($16.7pm0.6$ R$_{oplus}$), and an orbital period of
$P=2.650237pm0.000003$ d. Analysis of the spectral energy distribution of the
host star reveals that the planet orbits a bright ($mathrm{V}=8.049$ mag) and
young ($0.29^{+0.32}_{-0.19}$ Gyr) Am type star with $T_{rm
eff}=7690^{+400}_{-250}$ $rm{K}$, resulting in a highly irradiated planet with
an incident flux of $langle F rangle=7.24^{+0.68}_{-0.64}times$10$^9$ erg
s$^{-1}$ cm$^{-2}$ ($5300^{+500}_{-470}mathrm{S_{oplus}}$) and an equilibrium
temperature of $T_{eq}=2370pm70$ K. TESS photometry also reveals a secondary
eclipse with a depth of $127^{+4}_{-5}$ppm as well as the full phase curve of
the planet’s thermal emission in the red-optical. This has allowed us to
measure the dayside and nightside temperature of its atmosphere as
$T_mathrm{day}=3004pm64$ K and $T_mathrm{night}=2583pm63$ K, the second
hottest measured nightside temperature. The planet’s low day/night temperature
contrast ($sim$420 K) suggests very efficient heat transport between the
dayside and nightside hemispheres.

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