Kavli Affiliate: Sara Seager
| First 5 Authors: Katharine Hesse, Ismael Mireles, François Bouchy, Diana Dragomir, Solène Ulmer-Moll
| Summary:
We report the discovery and confirmation of two planets orbiting the
metal-poor Sun-like star, HD 35843 (TOI 4189). HD 35843 c is a temperate
sub-Neptune transiting planet with an orbital period of 46.96 days that was
first identified by Planet Hunters TESS. We combine data from TESS and
follow-up observations to rule out false-positive scenarios and validate the
planet. We then use ESPRESSO radial velocities to confirm the planetary nature
and characterize the planet’s mass and orbit. Further analysis of these RVs
reveals the presence of an additional planet, HD 35843 b, with a period of 9.90
days and a minimum mass of $5.84pm0.84$ $M_{oplus}$. For HD 35843 c, a joint
photometric and spectroscopic analysis yields a radius of $2.54 pm 0.08
R_{oplus}$, a mass of $11.32 pm 1.60 M_{oplus}$, and an orbital eccentricity
of $e = 0.15pm0.07$. With a bulk density of $3.80 pm 0.70$ g/cm$^3$, the
planet might be rocky with a substantial H$_2$ atmosphere or it might be a
“water world". With an equilibrium temperature of $sim$480 K, HD 35843 c is
among the coolest $sim 5%$ of planets discovered by TESS. Combined with the
host star’s relative brightness (V= 9.4), HD 35843 c is a promising target for
atmospheric characterization that will probe this sparse population of
temperate sub-Neptunes.
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