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

Creators: 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.

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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꜀ ≲ 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.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2022 February 6; revised 2022 May 29; accepted 2022 June 24; published 2022 August 12. The authors thank Daniel Foreman-Mackey for discussions regarding the parameterization of the transit models used in this work. The authors also thank Konstantin Batygin for discussions on the dynamical context of this planetary system. M.M. acknowledges support from the UCLA Cota-Robles Graduate Fellowship. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC21K0652), and the National Science Foundation (AST-1717000). D.D. acknowledges support from the TESS Guest Investigator Program grant 80NSSC22K0185 and NASA Exoplanet Research Program grant 18-2XRP18_2-0136. T.F. acknowledges support from the University of California President's Postdoctoral Fellowship Program. R.A.R. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1745301. P.D. is supported by a National Science Foundation (NSF) Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. J.M.A.M. is supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1842400. J.M.A.M. acknowledges the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant No. 1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank the time assignment committees of the University of California, the California Institute of Technology, NASA, and the University of Hawaii for supporting the TESS–Keck Survey with observing time at Keck Observatory. We thank NASA for funding associated with our Key Strategic Mission Support project. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff for support of HIRES and remote observing. We recognize and acknowledge the cultural role and reverence that the summit of Maunakea has within the indigenous Hawaiian community. We are deeply grateful to have the opportunity to conduct observations from this mountain. This paper is based on data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We also acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This article is also based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grants PGC2018-098153-B-C31. This work is also partly supported by JSPS KAKENHI grant No. JP17H04574, JP18H05439, JP20J21872, JP20K14521, JP21K20376, JST CREST grant No. JPMJCR1761, the Astrobiology Center of National Institutes of Natural Sciences (NINS; grant No. AB031010), and Grant-in-Aid for JSPS Fellows. This paper also includes data that are publicly available from the Mikulski Archive for Space Telescopes (MAST). Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This work also used computational and storage services associated with the Hoffman2 Shared Cluster provided by UCLA Institute for Digital Research and Education's Research Technology Group. Facilities: TESS - , Keck/HIRES - , MuSCAT - , MuSCAT2 - Software: We made use of the following publicly available Python modules: exoplanet (Foreman-Mackey et al. 2021), PyMC3 (Salvatier et al. 2016), theano (The Theano Development Team et al. 2016), LDTK (Parviainen & Aigrain 2015), RadVel (Fulton et al. 2018), RVSearch (Rosenthal et al. 2021), astropy (Astropy Collaboration et al.2013, 2018), isoclassify (Huber et al. 2017), lightkurve (Lightkurve Collaboration et al. 2018), matplotlib (Hunter 2007), numpy (Harris et al. 2020), scipy (Virtanen et al. 2020), rebound (Rein & Liu 2012), stardate (Angus et al. 2019a), TESS-SIP (Hedges et al. 2020), SpecMatch-Synth (Petigura et al. 2017), and pandas (McKinney 2010).

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