A search for young exoplanets in Sectors 1–5 of the TESS full-frame images

Abstract

Young (<1 Gyr) exoplanets represent a critically important area of exoplanet research, as they offer the opportunity to learn about the formation and early dynamic history of exoplanetary systems. However, finding young exoplanets is significantly complicated by the fast rotation and complex activity of their young host stars, which are often not well handled by state-of-the-art automatic pipelines. This work presents an alternative LOWESS-based pipeline focused specifically on detrending young stellar light curves from the 30-min cadence full-frame images produced by the Transiting Exoplanet Survey Satellite (TESS), and includes improvements such as automatic peak cutting of stellar variability and interpolation over masked transits to improve periodogram visibility and returned transit shapes. This work presents the details of the developed pipeline, along with initial results from its application to young stars within stellar associations in Sectors 1–5 of the TESS data. While no new exoplanet candidate signals were found in this work, interesting results included the recovery of all known 2-min TOIs around young stars in Sectors 1–5 from 30-min data alone, the recovery of the young exoplanet DS Tuc Ab, a number of young eclipsing binaries and a wide array of interesting rotation. A sensitivity analysis was also undertaken for each star, showing how the recovery of injected planets varied with both depth and period for each individual target. Challenges for future searches for young exoplanets are discussed, the largest being stellar rotation with periods less than 1 d and a lack of a large sample of confirmed young stars.

TOI-2076 and TOI-1807: Two Young, Comoving Planetary Systems within 50 pc Identified by TESS that are Ideal Candidates for Further Follow Up

“…43 Thus, there is value in identifying and characterizing young planets. This can be done through careful characterization of previously known exoplanet hosts or through targeted planet searches in samples of known young stars (e.g., Battley et al 2020;Nardiello et al 2020).…”

YOUNG Star detrending for Transiting Exoplanet Recovery (YOUNGSTER) – II. Using self-organizing maps to explore young star variability in sectors 1–13 of TESS data

“…Indeed, as Hippke et al (2019) illustrated in their Wotan detrending paper, most general detrending algorithms recovered only 37% of the 0.5 sized young planetary signals injected into young star light-curves, compared to approximately 99% of those injected into an older population. Battley et al (2020) and Nardiello et al (2021) recently broke this down further, illustrating how the recovery of planets injected into young-star light-curves varied with planetary radius/radius ratio and period, as well as stellar magnitude and rotation period. In both these cases recovery was seen to drop considerably when injected planetary radii fell below the Hot Jupiter size regime.…”

“…One of the main challenges hindering further young planet discoveries is the wide variety in photometric variability of young stars, as was explored in Battley et al (2020). This provides a significant challenge to traditional 'one-size-fits-most' detrending approaches, where often a single window size is chosen for simplicity.…”

“…The first paper in this series (Battley et al 2020, hereafter YOUNGSTER I) presented a new lowess-based detrending method which showed promise as a dedicated young-star detrending method, but also highlighted some of the challenging variability classes such as very short-period rotation (<1.5 day rotation periods). This paper, paper II, presents the results from the use of an unsupervised Self-Organising Map (SOM, Kohonen 1982Kohonen , 2001 as a tool to explore young star variability further, and acts as a first step into more targeted characterisation and sorting of young star variability for exoplanet searches.…”

Constraints on the mass and atmospheric composition and evolution of the low-density young planet DS Tuc A b

“…didates around young stars (e.g. Nardiello et al 2020;Battley et al 2020;Nardiello 2020), thanks to systematic observations of about 85% of the sky. Early discoveries of hot Jupiters around very young stars (Donati et al 2016;Yu et al 2017;Rizzuto et al 2020) suggested a larger frequency of close-in massive planets with respect to older stars.…”