TESS Spots a Super-puff: The Remarkably Low Density of TOI-1420b

November 2023 • 2023AJ....166..181Y

Authors • Yoshida, Stephanie • Vissapragada, Shreyas • Latham, David W. • Bieryla, Allyson • Thorngren, Daniel P. • Eastman, Jason D. • López-Morales, Mercedes • Barkaoui, Khalid • Beichman, Charles • Berlind, Perry • Buchave, Lars A. • Calkins, Michael L. • Ciardi, David R. • Collins, Karen A. • Cosentino, Rosario • Crossfield, Ian J. M. • Dai, Fei • DiTomasso, Victoria • Dowling, Nicholas • Esquerdo, Gilbert A. • Forés-Toribio, Raquel • Ghedina, Adriano • Goliguzova, Maria V. • Golub, Eli • Gonzales, Erica J. • Horta, Ferran Grau • Higuera, Jesus • Hoch, Nora • Horne, Keith • Howell, Steve B. • Jenkins, Jon M. • Klusmeyer, Jessica • Laloum, Didier • Lissauer, Jack J. • Logsdon, Sarah E. • Malavolta, Luca • Matson, Rachel A. • Matthews, Elisabeth C. • McLeod, Kim K. • Medina, Jennifer V. • Muñoz, Jose A. • Osborn, Hugh P. • Safonov, Boris • Schlieder, Joshua • Schmidt, Michael • Schweiker, Heidi • Seager, Sara • Sozzetti, Alessandro • Srdoc, Gregor • Stefánsson, Guđmundur • Strakhov, Ivan A. • Striegel, Stephanie • Villaseñor, Joel • Winn, Joshua N.

Abstract • We present the discovery of TOI-1420b, an exceptionally low-density (ρ = 0.08 ± 0.02 g cm^-3) transiting planet in a P = 6.96 days orbit around a late G-dwarf star. Using transit observations from TESS, LCOGT, Observatoire Privé du Mont, Whitin, Wendelstein, OAUV, Ca l'Ou, and KeplerCam, along with radial velocity observations from HARPS-N and NEID, we find that the planet has a radius of R _p = 11.9 ± 0.3R _⊕ and a mass of M _p = 25.1 ± 3.8M _⊕. TOI-1420b is the largest known planet with a mass less than 50M _⊕, indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b's envelope mass fraction to be ${f}_{\mathrm{env}}={82}_{-6}^{+7} \% $ , suggesting that runaway gas accretion occurred when its core was at most four to five times the mass of the Earth. TOI-1420b is similar to the planet WASP-107b in mass, radius, density, and orbital period, so a comparison of these two systems may help reveal the origins of close-in low-density planets. With an atmospheric scale height of 1950 km, a transmission spectroscopy metric of 580, and a predicted Rossiter-McLaughlin amplitude of about 17 m s^-1, TOI-1420b is an excellent target for future atmospheric and dynamical characterization.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023AJ....166..181Y
• PDF https://iopscience.iop.org/article/10.3847/1538-3881/acf858/pdf
• PREPRINT http://arxiv.org/abs/2309.09945
• DATA https://archive.gemini.edu/searchform/publication=2023AJ....166..181Y
• ELECTR https://doi.org/10.3847%2F1538-3881%2Facf858