A Search For Young Ultra-Short-Period Planets with TESS

Ultra-short-period (USP) planets, those with an orbital period less than a day, are a population of rare and extreme worlds that provide an opportunity to study the formation and evolution of small planets in ways that are more difficult for their longer period counterparts. Many of the significant changes a planet experiences occur on timescales of < 100 Myr, so studying planets across these ages is essential to uncovering mechanisms that shape planetary systems. However, active young stars can introduce large-amplitude photometric and spectroscopic variations, making detection and characterization difficult. Luckily, the very short transits of USP planets are separable even from the stellar signal of many rapidly rotating young stars, leading to more complete transit detection of young planets at the shortest periods. I present the development of a specialized pipeline for identification of candidate young transiting planets using TESS 2-minute data, which includes detrending designed to preserve transits in the face of rapid stellar rotation. I tested the pipeline on a set of injected transits, and found it to recover 66% of planets between 1 − 2R⊕ around stars smaller than the Sun. I applied the pipeline to a sample of 6600 young stars from the literature, and identified 51 planet candidates, including a young “twin” of 55 Cnc e and a surprise single-transit candidate with an orbital period likely longer than a month. This sample of candidates can be followed up to constrain the occurrence rate of young USP planets and explore the mechanisms shaping young systems, and this pipeline can be applied to much broader samples as TESS continues to monitor the whole sky with its new 200-second full frame image cadence.Astro 9