A 38 Million Year Old Neptune-Sized Planet in the Kepler Field

Abstract

Kepler 1627A is a G8V star previously known to host a 3.8 R ⊕ planet on a 7.2 day orbit. The star was observed by the Kepler space telescope because it is nearby (d = 329 pc) and it resembles the Sun. Here we show using Gaia kinematics, TESS stellar rotation periods, and spectroscopic lithium abundances that Kepler 1627 is a member of the 38 +6 −5 Myr old δ Lyr cluster. To our knowledge, this makes Kepler 1627Ab the youngest planet with a precise age yet found by the prime Kepler mission. The Kepler photometry shows two peculiarities: the average transit profile is asymmetric, and the individual transit times might be correlated with the local light curve slope. We discuss possible explanations for each anomaly. More importantly, the δ Lyr cluster is one of ∼10 3 coeval groups whose properties have been clarified by Gaia. Many other exoplanet hosts are candidate members of these clusters; their ages can be verified with the trifecta of Gaia, TESS, and ground-based spectroscopy.

Transit Hunt for Young and Maturing Exoplanets (THYME) VIII: a Pleiades-age association harboring two transiting planetary systems from Kepler

“…The previous challenge for Kepler was the lack of young associations. MELANGE-3 and the recently identified δ-Lyr cluster (Bouma et al 2021) demonstrate that the previous list of just four clusters in the Kepler field was incomplete and motivates the work for further searches in the Kepler, K 2, and CoRoT (Auvergne et al 2009) fields. In addition to surveys like Theia (Kounkel & Covey 2019;Kounkel et al 2020), the methods applied here may reveal a new population of young associations harboring known transiting systems.…”

“…The availability of precise parallaxes and proper motions for millions of stars from Gaia (Gaia Collaboration et al 2016Collaboration et al , 2021 has enabled the discovery of new coeval stellar associations (e.g., Meingast et al 2019;Kerr et al 2021), including the 40 Myr δ Lyr cluster that overlaps with the Kepler field (Bouma et al 2021). The FriendFinder code 1 (Tofflemire et al 2021) was designed to take advantage of Gaia data, by searching for potential co-moving 'friends' around a user-identified 1 https://github.com/adamkraus/Comove young star.…”

The GAPS Programme at TNG

“…Despite this, in recent years, the population of young planets has been growing significantly and planets have been found around young stellar cluster members like M44 and the Hyades (Quinn et al 2012(Quinn et al , 2014Mann et al 2016a;Rizzuto et al 2018;Vanderburg et al 2018), young stellar associations and moving groups (Benatti et al 2019;Mann et al 2020;Rizzuto et al 2020;Tofflemire et al 2021;Newton et al 2021;Mann et al 2021), and single young stars (David et al 2019;Plavchan et al 2020;Carleo et al A&A proofs: manuscript no. 43743corr 2021; Bouma et al 2021). However, only a few sample of young exoplanets with ages < 0.5 − 1 Gyr have well-constrained ages, (upper-limit) masses, and radii, demonstrating a broad variety of planets with densities included between <0.5-1 ρ ⊕ (see, e.g., Benatti et al 2021) and 2-3 ρ ⊕ (see, e.g, Barragán et al 2019Barragán et al , 2022b.…”

“…Indeed, the strong starspots' activity on the stellar surface (typical of young stars with ages 1 Gyr) generates (periodical) important variations of the star's flux both in the photometric and spectroscopic time series, that can mask the planets' signals if not appropriately modeled. Despite this, in recent years, the population of young planets has been growing significantly; planets have been found around young stellar cluster members like M44 and the Hyades (Quinn et al 2012(Quinn et al , 2014Mann et al 2016a;Rizzuto et al 2018;Vanderburg et al 2018), young stellar associations and moving groups (Benatti et al 2019;Mann et al 2020;Rizzuto et al 2020;Tofflemire et al 2021;Newton et al 2021;Mann et al 2021), and single young stars (David et al 2019;Plavchan et al 2020;Carleo et al 2021;Bouma et al 2021). However, only a few sample of young exoplanets with ages < 0.5 − 1 Gyr have well-constrained ages, (upper-limit) masses, and radii, showing a large variety of planets with densities included between <0.5-1 ρ ⊕ (see, e.g., A&A proofs: manuscript no.…”