$textit{TESS}$ Giants Transiting Giants I: A Non-inflated Hot Jupiter Orbiting a Massive Subgiant

Kavli Affiliate: Roland K. Vanderspek

| First 5 Authors: Nicholas Saunders, Samuel K. Grunblatt, , ,

| Summary:

While the population of confirmed exoplanets continues to grow, the sample of
confirmed transiting planets around evolved stars is still limited. We present
the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC
176956893), a massive evolved subgiant ($M_star= 1.53 pm 0.12 M_odot$,
$R_star= 2.90 pm 0.14 R_odot$) in the $textit{TESS}$ Southern Continuous
Viewing Zone. The planet was flagged as a false positive by the $textit{TESS}$
Quick-Look Pipeline due to periodic systematics introducing a spurious depth
difference between even and odd transits. Using a new pipeline to remove
background scattered light in $textit{TESS}$ Full Frame Image (FFI) data, we
combine space-based $textit{TESS}$ photometry, ground-based photometry, and
ground-based radial velocity measurements to report a planet radius of $R_p=
1.017 pm 0.051 R_J$ and mass of $M_p= 0.65 pm 0.16 M_J$. For a planet so
close to its star, the mass and radius of TOI-2184b are unusually well matched
to those of Jupiter. We find that the radius of TOI-2184b is smaller than
theoretically predicted based on its mass and incident flux, providing a
valuable new constraint on the timescale of post-main-sequence planet
inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting
planets around faint ($textit{TESS}$ magnitude $>12$) post-main sequence stars
and suggests that many more similar systems are waiting to be detected in the
$textit{TESS}$ FFIs, whose confirmation may elucidate the final stages of
planetary system evolution.

| Search Query: ArXiv Query: search_query=au:”Roland K. Vanderspek”&id_list=&start=0&max_results=10

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