The Astronomical Journal (Jan 2022)

TESS Hunt for Young and Maturing Exoplanets (THYME). VII. Membership, Rotation, and Lithium in the Young Cluster Group-X and a New Young Exoplanet

  • Elisabeth R. Newton,
  • Rayna Rampalli,
  • Adam L. Kraus,
  • Andrew W. Mann,
  • Jason L. Curtis,
  • Andrew Vanderburg,
  • Daniel M. Krolikowski,
  • Daniel Huber,
  • Grayson C. Petter,
  • Allyson Bieryla,
  • Benjamin M. Tofflemire,
  • Pa Chia Thao,
  • Mackenna L. Wood,
  • Ronan Kerr,
  • Boris S. Safanov,
  • Ivan A. Strakhov,
  • David R. Ciardi,
  • Steven Giacalone,
  • Courtney D. Dressing,
  • Holden Gill,
  • Arjun B. Savel,
  • Karen A. Collins,
  • Peyton Brown,
  • Felipe Murgas,
  • Keisuke Isogai,
  • Norio Narita,
  • Enric Palle,
  • Samuel N. Quinn,
  • Jason D. Eastman,
  • Gábor Fűrész,
  • Bernie Shiao,
  • Tansu Daylan,
  • Douglas A. Caldwell,
  • George R. Ricker,
  • Roland Vanderspek,
  • Sara Seager,
  • Joshua N. Winn,
  • Jon M. Jenkins,
  • David W. Latham

DOI
https://doi.org/10.3847/1538-3881/ac8154
Journal volume & issue
Vol. 164, no. 3
p. 115

Abstract

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The public, all-sky surveys Gaia and TESS provide the ability to identify new young associations and determine their ages. These associations enable study of planetary evolution by providing new opportunities to discover young exoplanets. A young association was recently identified by Tang et al. and Fürnkranz et al. using astrometry from Gaia (called “Group-X” by the former). In this work, we investigate the age and membership of this association, and we validate the exoplanet TOI 2048 b, which was identified to transit a young, late G dwarf in Group-X using photometry from TESS. We first identified new candidate members of Group-X using Gaia EDR3 data. To infer the age of the association, we measured rotation periods for candidate members using TESS data. The clear color–period sequence indicates that the association is the same age as the 300 ± 50 Myr old NGC 3532. We obtained optical spectra for candidate members that show lithium absorption consistent with this young age. Further, we serendipitously identify a new, small association nearby Group-X, which we call MELANGE-2. Lastly, we statistically validate TOI 2048 b, which is a 2.1 ± 0.2 R _⊕ radius planet on a 13.8-day orbit around its 300 Myr old host star.

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