TESS Giants Transiting Giants II: The hottest Jupiters orbiting evolved stars

Kavli Affiliate: Alan M. Levine

| First 5 Authors: Samuel K. Grunblatt, Nicholas Saunders, Meng Sun, Ashley Chontos, Melinda Soares-Furtado

| Summary:

Giant planets on short-period orbits are predicted to be inflated and
eventually engulfed by their host stars. However, the detailed timescales and
stages of these processes are not well known. Here we present the discovery of
three hot Jupiters (P $<$ 10 d) orbiting evolved, intermediate-mass stars
($M_star$ $approx$ 1.5 M$_odot$, 2 R$_odot$ $<$ $R_star < $ 5 R$_odot$).
By combining tess photometry with ground-based photometry and radial velocity
measurements, we report masses and radii for these three planets between 0.4
and 1.8 M$_mathrm{J}$ and 0.8 and 1.8 R$_mathrm{J}$. planet has the shortest
period (P=period) of any planet discovered around a red giant star to date.
Both planettwo and planetthree appear to be inflated, but planet does not
show any sign of inflation. The large radii and relatively low masses of
planettwo and planetthree place them among the lowest density hot Jupiters
currently known, while planet is conversely one of the highest. All three
planets have orbital eccentricities below 0.2. The large spread in radii for
these systems implies that planet inflation has a complex dependence on planet
mass, radius, incident flux, and orbital properties. We predict that planet
has the shortest orbital decay timescale of any planet currently known, but do
not detect any orbital decay in this system. Transmission spectroscopy of
planettwo would provide a favorable opportunity for the detection of water,
carbon dioxide and carbon monoxide features in the atmosphere of a planet
orbiting an evolved star, and could yield new information about planet
formation and atmospheric evolution.

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