TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data

We report the first discovery of a transiting circumbinary planet detected from a single sector of Transiting Exoplanet Survey Satellite (TESS) data. During Sector 21, the planet TIC 172900988b transited the primary star and then five days later it transited the secondary star. The binary is itself eclipsing, with a period P approximate to 19.7 days and an eccentricity e approximate to 0.45. Archival data from ASAS-SN, Evryscope, KELT, and SuperWASP reveal a prominent apsidal motion of the binary orbit, caused by the dynamical interactions between the binary and the planet. A comprehensive photodynamical analysis of the TESS, archival and follow-up data yields stellar masses and radii of M (1) = 1.2384 +/- 0.0007 M (circle dot) and R (1) = 1.3827 +/- 0.0016 R (circle dot) for the primary and M (2) = 1.2019 +/- 0.0007 M (circle dot) and R (2) = 1.3124 +/- 0.0012 R (circle dot) for the secondary. The radius of the planet is R (3) = 11.25 +/- 0.44 R (circle plus) (1.004 +/- 0.039R (Jup)). The planet's mass and orbital properties are not uniquely determined-there are six solutions with nearly equal likelihood. Specifically, we find that the planet's mass is in the range of 824 less than or similar to M (3) less than or similar to 981 M (circle plus) (2.65 less than or similar to M (3) less than or similar to 3.09M (Jup)), its orbital period could be 188.8, 190.4, 194.0, 199.0, 200.4, or 204.1 days, and the eccentricity is between 0.02 and 0.09. At V = 10.141 mag, the system is accessible for high-resolution spectroscopic observations, e.g., the Rossiter-McLaughlin effect and transit spectroscopy.

Automated summary

In this study, the first transiting circumbinary planet detected from a single sector of TESS data is reported. The binary system itself is eclipsing, with a period of approximately 19.7 days and an eccentricity of approximately 0.45. The comprehensive analysis reveals that the mass and orbital properties of the planet are not uniquely determined, with six potential solutions of nearly equal likelihood.