Discovering Circumbinary Planets with TESS

Unraveling the characteristics of circumbinary planets (CBPs) is of fundamental value in exoplanetary astronomy as this new class of planetary bodies enables researchers to address questions regarding the formation, migration, evolution and habitability of planets in a broader context. Thanks to the successful operation of the Kepler and TESS telescopes, 14 such planets have already been detected and some trends seem to have emerged. For instance, the orbits of several of these bodies is close to the boundary of stability, and they all reside between major mean-motion resonances with their host binaries. It is also widely accepted that the currently known CBPs formed at large distances and migrated to their current orbits, with those close to the stability limit being Neptune-sized or slightly
larger. Despite these advances, some pressing questions still stand. For instance, the efficiency of the formation and migration of CBPs is unknown, and so are their occurrence frequency, orbital architecture, and the population characteristics of their host binaries. The answers to these questions are of significant value, not only to our understanding of the formation and evolution of circumbinary planets, but also, more broadly, to furthering our knowledge of planet formation, planet migration, and population characteristics of general planetary systems. To address these questions, a CBP population larger than the current 14 is required. The latter is the goal of our proposed project. We propose to use the data from the TESS telescope to detect several tens to more than a hundred transiting CBPs around TESS eclipsing binaries. Because TESS observes segments of the sky for only 27.4 days, it is not possible to use the same detection technique as that used in detecting Kepler CBPs (i.e., detecting transits that span several orbital periods). Instead, we plan to use a unique observational signature of transiting CBPs, namely, the occurrence of multiple transits during one conjunction. This characteristics of CBPs has been shown to be a powerful detection technique for identifying planets around eclipsing binaries (EBs). We plan to apply this technique to a catalog of ~400,000 TESS EBs. This technique also allows for probing planetary periods longer than even the year-long observations of the ecliptic pole, thereby enhancing the science return of TESS, and maximizing the longperiod,
temperate planet yield. Our proposed project is extremely timely. The ~400,000 TESS EB light-curves that will be used in this project is 200 times more
than the entire Kepler EB light-curves that were used to detect the current CBPs. With such a large data set, our proposed project will increase the population of CBPs by possibly an order of magnitude (even at its lowest yield, it will increase the number of CBPs by ~2.6 times) transforming the field from the current realm of individual detections to population statistic. These detections will further our knowledge of the formation and dynamical evolution of planets, enabling us to obtain a more expanded view of other planetary systems. This proposal is in direct relevance to NASA’s Strategic Goal 1(expand human knowledge through new scientific discoveries), NASA Strategic Goal 1.1 (understanding the Sun, Earth, Solar System, and Universe), and the scope of the XRP program, the detection and characterization of exoplanetary systems, and the origin of exoplanets.