TESS Hunt for Young and Maturing Exoplanets (THYME). V. A Sub-Neptune Transiting a Young Star in a Newly Discovered 250 Myr Association
Abstract
The detection and characterization of young planetary systems offer a direct path to study the processes that shape planet evolution. We report on the discovery of a sub-Neptune-sized planet orbiting the young star HD 110082 (TOI-1098). Transit events we initially detected during TESS Cycle 1 are validated with time-series photometry from Spitzer. High-contrast imaging and high-resolution, optical spectra are also obtained to characterize the stellar host and confirm the planetary nature of the transits. The host star is a late-F dwarf (M⋆ = 1.2M⊙) with a low-mass, M dwarf binary companion (M⋆ = 0.26M⊙) separated by nearly one arcminute (∼6200 au). Based on its rapid rotation and Lithium absorption, HD 110082 is young, but is not a member of any known group of young stars (despite proximity to the Octans association). To measure the age of the system, we search for coeval, phase-space neighbors and compile a sample of candidate siblings to compare with the empirical sequences of young clusters and to apply quantitative age-dating techniques. In doing so, we find that HD 110082 resides in a new young stellar association we designate MELANGE-1, with an age of ${250}_{-70}^{+50}$ Myr. Jointly modeling the TESS and Spitzer light curves, we measure a planetary orbital period of 10.1827 days and radius of Rp = 3.2 ± 0.1R⊕. HD 110082 b's radius falls in the largest 12% of field-age systems with similar host-star mass and orbital period. This finding supports previous studies indicating that young planets have larger radii than their field-age counterparts.
- Publication:
-
The Astronomical Journal
- Pub Date:
- April 2021
- DOI:
- 10.3847/1538-3881/abdf53
- arXiv:
- arXiv:2102.06066
- Bibcode:
- 2021AJ....161..171T
- Keywords:
-
- Exoplanet astronomy;
- Exoplanets;
- Mini Neptunes;
- Stellar astronomy;
- Wide binary stars;
- Moving clusters;
- Stellar ages;
- Transits;
- 486;
- 498;
- 1063;
- 1583;
- 1801;
- 1076;
- 1581;
- 1711;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted to AJ, 20 figures, 7 tables, 1 appendix