The TESS-Keck Survey. XIII. An Eccentric Hot Neptune with a Similar-mass Outer Companion around TOI-1272

September 2022 • 2022AJ....164...97M

Authors • MacDougall, Mason G. • Petigura, Erik A. • Fetherolf, Tara • Beard, Corey • Lubin, Jack • Angelo, Isabel • Batalha, Natalie M. • Behmard, Aida • Blunt, Sarah • Brinkman, Casey • Chontos, Ashley • Crossfield, Ian J. M. • Dai, Fei • Dalba, Paul A. • Dressing, Courtney • Fulton, Benjamin • Giacalone, Steven • Hill, Michelle L. • Howard, Andrew W. • Huber, Daniel • Isaacson, Howard • Kane, Stephen R. • Kosiarek, Molly • Mayo, Andrew • Močnik, Teo • Akana Murphy, Joseph M. • Pidhorodetska, Daria • Polanski, Alex • Rice, Malena • Robertson, Paul • Rosenthal, Lee J. • Roy, Arpita • Rubenzahl, Ryan A. • Scarsdale, Nicholas • Turtelboom, Emma V. • Tyler, Dakotah • Van Zandt, Judah • Weiss, Lauren M. • Esparza-Borges, Emma • Fukui, Akihiko • Isogai, Keisuke • Kawauchi, Kiyoe • Mori, Mayuko • Murgas, Felipe • Narita, Norio • Nishiumi, Taku • Palle, Enric • Parviainen, Hannu • Watanabe, Noriharu • Jenkins, Jon M. • Latham, David W. • Ricker, George R. • Seager, S. • Vanderspek, Roland K. • Winn, Joshua N. • Bieryla, Allyson • Caldwell, Douglas A. • Dragomir, Diana • Fausnaugh, M. M. • Mireles, Ismael • Rodriguez, David R.

Abstract • We report the discovery of an eccentric hot Neptune and a non-transiting outer planet around TOI-1272. We identified the eccentricity of the inner planet, with an orbital period of 3.3 days and R p,b = 4.1 ± 0.2 R , based on a mismatch between the observed transit duration and the expected duration for a circular orbit. Using ground-based radial velocity (RV) measurements from the HIRES instrument at the Keck Observatory, we measured the mass of TOI-1272b to be M p,b = 25 ± 2 M . We also confirmed a high eccentricity of e b = 0.34 ± 0.06, placing TOI-1272b among the most eccentric well-characterized sub-Jovians. We used these RV measurements to also identify a non-transiting outer companion on an 8.7 day orbit with a similar mass of M p,c sin i = 27 ± 3 M and e c ≲ 0.35. Dynamically stable planet-planet interactions have likely allowed TOI-1272b to avoid tidal eccentricity decay despite the short circularization timescale expected for a close-in eccentric Neptune. TOI-1272b also maintains an envelope mass fraction of f env ≈ 11% despite its high equilibrium temperature, implying that it may currently be undergoing photoevaporation. This planet joins a small population of short-period Neptune-like planets within the "Hot Neptune Desert" with a poorly understood formation pathway.


IPAC Authors


Benjamin Fulton

Assistant Scientist