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 GillArjun 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

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


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.

Original languageEnglish (US)
Article number115
JournalAstronomical Journal
Issue number3
StatePublished - Sep 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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