Searching for GEMS: TOI-5688 A b, a Low-density Giant Orbiting a High-metallicity Early M-dwarf
Kobulnicky, Henry A.; Cochran, William D.; Mahadevan, Suvrath; Logsdon, Sarah E.; Monson, Andrew; McElwain, Michael W.; Cañas, Caleb I.; Kanodia, Shubham; Ninan, Joe P.; Bender, Chad F.; Diddams, Scott A.; Halverson, Samuel; Hearty, Fred; Robertson, Paul; Roy, Arpita; Schwab, Christian; Han, Te; Lin, Andrea S. J.; Alvarado-Montes, Jaime A.; Blake, Cullen H.; Libby-Roberts, Jessica; Reji, Varghese; Gupta, Arvind F.; Stefansson, Gudmundur; Ojha, Devendra K.; Swaby, Tera N.; Wright, Jason; Larsen, Alexander; Evans, Nez; Choi, Philip I.; Santomenna, Sage; Winnick, Isabelle; Yu, Larry; Bernabó, Lia Marta
India, United States, Australia, Germany, Netherlands
Abstract
We present the discovery of a low-density planet orbiting the high-metallicity early M-dwarf TOI-5688 A b. This planet was characterized as part of the search for transiting giant planets (R ≳ 8 R⊕) through the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey. The planet was discovered with the Transiting Exoplanet Survey Satellite, and characterized with ground-based transits from Red Buttes Observatory, the Table Mountain Observatory of Pomona College, and radial velocity (RV) measurements with the Habitable-Zone Planet Finder on the 10 m Hobby Eberly Telescope and NEID on the WIYN 3.5 m telescope. From the joint fit of transit and RV data, we measure a planetary mass and radius of 124 ± 24 M⊕ (0.39 ± 0.07 MJ) and 10.4 ± 0.7 R⊕ (0.92 ± 0.06 RJ), respectively. The spectroscopic and photometric analysis of the host star TOI-5688 A shows that it is a metal-rich ([Fe/H] = 0.47 ± 0.16 dex) M2V star, favoring the core-accretion formation pathway as the likely formation scenario for this planet. Additionally, Gaia astrometry suggests the presence of a wide-separation binary companion, TOI-5688 B, which has a projected separation of ~5″ (1110 au) and is an M4V, making TOI-5688 A b part of the growing number of GEMS in wide-separation binary systems. *Based on observations obtained with the Hobby–Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.