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Kepler and the Behemoth: Three Mini-Neptunes in a 40 Million Year Old Association

Bouma, L. G. and Kerr, R. and Curtis, J. L. and Isaacson, H. and Hillenbrand, L. A. and Howard, A. W. and Kraus, A. L. and Bieryla, A. and Latham, D. W. and Petigura, E. A. and Huber, D. (2022) Kepler and the Behemoth: Three Mini-Neptunes in a 40 Million Year Old Association. Astronomical Journal, 164 (5). Art. NO. 215. ISSN 0004-6256. doi:10.3847/1538-3881/ac93ff.

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Stellar positions and velocities from Gaia are yielding a new view of open cluster dispersal. Here we present an analysis of a group of stars spanning Cepheus (l = 100°) to Hercules (l = 40°), hereafter the Cep-Her complex. The group includes four Kepler objects of interest: Kepler-1643 b (Rₚ = 2.32 ± 0.13 R_⊕, P = 5.3 days), KOI-7368 b (Rₚ = 2.22 ± 0.12 R_⊕, P = 6.8 days), KOI-7913 Ab (Rₚ = 2.34 ± 0.18 R_⊕, P = 24.2 days), and Kepler-1627 Ab (Rₚ = 3.85 ± 0.11 R_⊕, P = 7.2 days). The latter Neptune-sized planet is in part of the Cep-Her complex called the δ Lyr cluster. Here we focus on the former three systems, which are in other regions of the association. Based on kinematic evidence from Gaia, stellar rotation periods from TESS, and spectroscopy, these three objects are also ≈40 million years (Myr) old. More specifically, we find that Kepler-1643 is 46⁺⁹₋₇ Myr old, based on its membership in a dense subcluster of the complex called RSG-5. KOI-7368 and KOI-7913 are 36⁺¹⁰₋₈ Myr old, and are in a diffuse region that we call CH-2. Based on the transit shapes and high-resolution imaging, all three objects are most likely planets, with false-positive probabilities of 6 × 10⁻⁹, 4 × 10⁻³, and 1 × 10⁻⁴ for Kepler-1643, KOI-7368, and KOI-7913, respectively. These planets demonstrate that mini-Neptunes with sizes of ≈2 Earth radii exist at ages of 40 Myr.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemDiscussion Paper
Bouma, L. G.0000-0002-0514-5538
Kerr, R.0000-0002-6549-9792
Curtis, J. L.0000-0002-2792-134X
Isaacson, H.0000-0002-0531-1073
Howard, A. W.0000-0001-8638-0320
Kraus, A. L.0000-0001-9811-568X
Bieryla, A.0000-0001-6637-5401
Latham, D. W.0000-0001-9911-7388
Petigura, E. A.0000-0003-0967-2893
Huber, D.0000-0001-8832-4488
Additional Information:L.G.B. is supported by the Heising-Simons Foundation 51 Pegasi b Fellowship and the NASA TESS GI Program (80NSSC21K0335 and 80NSSC22K0298). R.K. is supported by the Heising-Simons Foundation. J.L.C. is supported by NSF AST-2009840 and the NASA TESS GI Program (80NSSC22K0299). D.H. is supported by the Alfred P. Sloan Foundation and NASA (80NSSC19K0597).
Group:Astronomy Department
Funding AgencyGrant Number
Heising-Simons Foundation51 Pegasi b Fellowship
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:5
Record Number:CaltechAUTHORS:20221103-652041800.15
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117698
Deposited By: Research Services Depository
Deposited On:15 Nov 2022 18:29
Last Modified:15 Nov 2022 18:29

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