학술논문
TESS Spots a Super-Puff: The Remarkably Low Density of TOI-1420b
Document Type
Working Paper
Author
Yoshida, Stephanie; Vissapragada, Shreyas; Latham, David W.; Bieryla, Allyson; Thorngren, Daniel P.; Eastman, Jason D.; López-Morales, Mercedes; Barkaoui, Khalid; Beichmam, 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.
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Subject
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Abstract
We present the discovery of TOI-1420b, an exceptionally low-density ($\rho = 0.08\pm0.02$ g cm$^{-3}$) transiting planet in a $P = 6.96$ day orbit around a late G dwarf star. Using transit observations from TESS, LCOGT, OPM, 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 $\pm$ 0.3 $R_\Earth$ and a mass of $M_p$ = 25.1 $\pm$ 3.8 $M_\Earth$. TOI-1420b is the largest-known planet with a mass less than $50M_\Earth$, indicating that it contains a sizeable envelope of hydrogen and helium. We determine TOI-1420b's envelope mass fraction to be $f_{env} = 82^{+7}_{-6}\%$, suggesting that runaway gas accretion occurred when its core was at most $4-5\times$ 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.