TESS's Circumbinary Planet TOI-1338b / EBLM J0608-59b May Not Be Alone...

Circumbinary planets, which orbit both stars of a binary system, challenge our understanding of planet formation and orbital evolution. Planet formation around binary stars was thought to be difficult, and therefore these circumbinary planets were confined to the realm of science-fiction, until the discovery of Kepler-16b in 2011. Since then, 15 circumbinary planets have been discovered in 13 systems by transit missions.

TESS recently discovered its first confirmed circumbinary planet, TOI-1338b. Located in the mission’s continuous viewing zone and confirmed with ground-based photometry. Observed as part of the BEBOP (Binaries Escorted By Orbiting Planets) radial velocity survey, we combine ESPRESSO and HARPS radial velocity data in an attempt to confirm TOI-1338b and constrain it’s mass. With no sign of TOI-1338b in our current data we can place a 3-sigma upper limit on the mass at 12 Earth masses, a low-density planet.

Here I present our preliminary results on the system, including a candidate second planet. If confirmed, this would make TOI-1338 the second ever multi-planetary circumbinary planet system, and the first circumbinary planet discovered by radial velocity data.