2mass-planck-allsky

A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620

June 2022 • 2022AJ....163..269R

Authors • Reefe, Michael A. • Luque, Rafael • Gaidos, Eric • Beard, Corey • Plavchan, Peter P. • Cointepas, Marion • Cale, Bryson L. • Palle, Enric • Parviainen, Hannu • Feliz, Dax L. • Eastman, Jason • Stassun, Keivan • Gagné, Jonathan • Jenkins, Jon M. • Boyd, Patricia T. • Kidwell, Richard C. • McDermott, Scott • Collins, Karen A. • Fong, William • Guerrero, Natalia • Almenara-Villa, Jose-Manuel • Bean, Jacob • Beichman, Charles A. • Berberian, John • Bieryla, Allyson • Bonfils, Xavier • Bouchy, François • Brady, Madison • Bryant, Edward M. • Cacciapuoti, Luca • Cañas, Caleb I. • Ciardi, David R. • Collins, Kevin I. • Crossfield, Ian J. M. • Dressing, Courtney D. • Eigmüller, Philipp • El Mufti, Mohammed • Esparza-Borges, Emma • Fukui, Akihiko • Gao, Peter • Geneser, Claire • Gnilka, Crystal L. • Gonzales, Erica • Gupta, Arvind F. • Halverson, Sam • Hearty, Fred • Howell, Steve B. • Irwin, Jonathan • Kanodia, Shubham • Kasper, David • Kodama, Takanori • Kostov, Veselin • Latham, David W. • Lendl, Monika • Lin, Andrea • Livingston, John H. • Lubin, Jack • Mahadevan, Suvrath • Matson, Rachel • Matthews, Elisabeth • Murgas, Felipe • Narita, Norio • Newman, Patrick • Ninan, Joe • Osborn, Ares • Quinn, Samuel N. • Robertson, Paul • Roy, Arpita • Schlieder, Joshua • Schwab, Christian • Seifahrt, Andreas • Smith, Gareth D. • Sohani, Ahmad • Stefánsson, Guðmundur • Stevens, Daniel • Stürmer, Julian • Tanner, Angelle • Terrien, Ryan • Teske, Johanna • Vermilion, David • Wang, Sharon X. • Wittrock, Justin • Wright, Jason T. • Zechmeister, Mathias • Zohrabi, Farzaneh

Abstract • We present the validation of a transiting low-density exoplanet orbiting the M2.5 dwarf TOI 620 discovered by the NASA Transiting Exoplanet Survey Satellite (TESS) mission. We utilize photometric data from both TESS and ground-based follow-up observations to validate the ephemerides of the 5.09 day transiting signal and vet false-positive scenarios. High-contrast imaging data are used to resolve the stellar host and exclude stellar companions at separations ≳0.″2. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with multiple precision radial velocity (PRV) spectrographs to confirm the planetary nature of the transiting exoplanet. We calculate a 5σ upper limit of M P < 7.1 M and ρ P < 0.74 g cm-3, and we identify a nontransiting 17.7 day candidate. We also find evidence for a substellar (1-20 M J ) companion with a projected separation ≲20 au from a combined analysis of Gaia, adaptive optics imaging, and RVs. With the discovery of this outer companion, we carry out a detailed exploration of the possibilities that TOI 620 b might instead be a circum-secondary planet or a pair of eclipsing binary stars orbiting the host in a hierarchical triple system. We find, under scrutiny, that we can exclude both of these scenarios from the multiwavelength transit photometry, thus validating TOI 620 b as a low-density exoplanet transiting the central star in this system. The low density of TOI 620 b makes it one of the most amenable exoplanets for atmospheric characterization, such as with the James Webb Space Telescope and Ariel, validated or confirmed by the TESS mission to date.

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David Ciardi

Senior Scientist