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

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.
Bibliographical reference

The Astronomical Journal

Advertised on:
9
2022
Number of authors
61
IAC number of authors
7
Citations
3
Refereed citations
2
Description
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.
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