The First Habitable Zone Earth-sized Planet from TESS. I: Validation of the TOI-700 System

Creators: Gilbert, Emily A.; Barclay, Thomas; Schlieder, Joshua E.; Quintana, Elisa V.; Hord, Benjamin J.; Kostov, Veselin B.; Lopez, Eric D.; Rowe, Jason F.; Hoffman, Kelsey; Walkowicz, Lucianne M.; Silverstein, Michele L.; Rodriguez, Joseph E.; Vanderburg, Andrew; Suissa, Gabrielle; Airapetian, Vladimir S.; Clement, Matthew S.; Raymond, Sean N.; Mann, Andrew W.; Kruse, Ethan; Lissauer, Jack J.; Colón, Knicole D.; Kopparapu, Ravi kumar; Kreidberg, Laura; Zieba, Sebastian; Collins, Karen A.; Quinn, Samuel N.; Howell, Steve B.; Ziegler, Carl; Vrijmoet, Eliot Halley; Adams, Fred C.; Arney, Giada N.; Boyd, Patricia T.; Brande, Jonathan; Burke, Christopher J.; Cacciapuoti, Luca; Chance, Quadry; Christiansen, Jessie L.; Covone, Giovanni; Daylan, Tansu; Dineen, Danielle; Dressing, Courtney D.; Essack, Zahra; Fauchez, Thomas J.; Galgano, Brianna; Howe, Alex R.; Kaltenegger, Lisa; Kane, Stephen R.; Lam, Christopher; Lee, Eve J.; Lewis, Nikole K.; Logsdon, Sarah E.; Mandell, Avi M.; Monsue, Teresa; Mullally, Fergal; Mullally, Susan E.; Paudel, Rishi; Pidhorodetska, Daria; Plavchan, Peter; Tañón Reyes, Naylynn; Rinehart, Stephen A.; Rojas-Ayala, Bárbara; Smith, Jeffrey C.; Stassun, Keivan G.; Tenenbaum, Peter; Vega, Laura D.; Villanueva, Geronimo L.; Wolf, Eric T.; Youngblood, Allison; Ricker, George R.; Vanderspek, Roland K.; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Bakos, Gáspár Á.; Briceño, César; Ciardi, David R.; Cloutier, Ryan; Conti, Dennis M.; Couperus, Andrew; Di Sora, Mario; Eisner, Nora L.; Everett, Mark E.; Gan, Tianjun; Hartman, Joel D.; Henry, Todd; Isopi, Giovanni; Jao, Wei-Chun; Jensen, Eric L. N.; Law, Nicholas; Mallia, Franco; Matson, Rachel A.; Shappee, Benjamin J.; Wood, Mackenna Lee; Winters, Jennifer G.

Abstract

We present the discovery and validation of a three-planet system orbiting the nearby (31.1 pc) M2 dwarf star TOI-700 (TIC 150428135). TOI-700 lies in the TESS continuous viewing zone in the Southern Ecliptic Hemisphere; observations spanning 11 sectors reveal three planets with radii ranging from 1 R⊕ to 2.6 R⊕ and orbital periods ranging from 9.98 to 37.43 days. Ground-based follow-up combined with diagnostic vetting and validation tests enables us to rule out common astrophysical false-positive scenarios and validate the system of planets. The outermost planet, TOI-700 d, has a radius of 1.19 ± 0.11 R⊕ and resides within a conservative estimate of the host star's habitable zone, where it receives a flux from its star that is approximately 86% of Earth's insolation. In contrast to some other low-mass stars that host Earth-sized planets in their habitable zones, TOI-700 exhibits low levels of stellar activity, presenting a valuable opportunity to study potentially rocky planets over a wide range of conditions affecting atmospheric escape. While atmospheric characterization of TOI-700 d with the James Webb Space Telescope (JWST) will be challenging, the larger sub-Neptune, TOI-700 c (R = 2.63 R⊕), will be an excellent target for JWST and future space-based observatories. TESS is scheduled to once again observe the Southern Hemisphere, and it will monitor TOI-700 for an additional 11 sectors in its extended mission. These observations should allow further constraints on the known planet parameters and searches for additional planets and transit timing variations in the system.

Additional Information

© 2020 The American Astronomical Society. Received 2019 December 24; revised 2020 July 2; accepted 2020 July 10; published 2020 August 14. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the observations in the paper made use of the High-Resolution Imaging instrument Zorro at Gemini South. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. 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 makes use of observations from the LCOGT network. E.A.G. thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining grant #1829740, the Brinson Foundation, and the Moore Foundation; her participation in the program has benefited this work. E.A.G. and E.V.Q. are thankful for support from GSFC Sellers Exoplanet Environments Collaboration (SEEC), which is funded by the NASA Planetary Science Division's Internal Scientist Funding Model. J.F.R. acknowledges research funding support from the Canada Research Chairs program and NSERC Discovery Program. This research was enabled, in part, by support provided by Calcul Québec (www.calculquebec.ca) and ComputeCanada (www.computecanada.ca). A.V.'s work was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. R.C. is supported by a NASA grant in support of the TESS science mission. C.D.D acknowledges support from the NASA TESS Guest Investigator Program through grant 80NSSC18K1583. B.J.S. is supported by NASA grant 80NSSC19K1717 and NSF grants AST-1908952, AST-1920392, and AST-1911074. B.R-A acknowledges the funding support from FONDECYT through grant 11181295. J.G.W. is supported by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow. V.S.A. was supported by Sellers Exoplanetary Environments Collaboration (SEEC) Internal Scientist Funding Model (ISFM) at NASA GSFC and NICER Cycle 1 GO program. Facilities: ASAS-SN - , CTIO:0.9 m (2048x2046 Tek2K CCD) - , CTIO:1.5 m (CHIRON) - , Exoplanet Archive - , Gaia - , Gemini:South (Zorro) - , MAST - , LCOGT - , SOAR (Goodman Spectrograph - , HRcam) - , TESS - , WISE - Software: AstroImageJ (Collins et al. 2017), astropy (Astropy Collaboration et al. 2013, 2018), celerite (Foreman-Mackey et al. 2017; Foreman-Mackey 2018), emcee (Foreman-Mackey et al. 2013), exoplanet (Foreman-Mackey 2018), DAVE (Kostov et al. 2019a), Forecaster (Chen & Kipping 2017), IPython (Perez & Granger 2007), Jupyter (Kluyver et al. 2016), Lightkurve (Lightkurve Collaboration et al. 2018), M_-M_K- (Mann et al. 2019), Matplotlib (Hunter 2007), Mercury6 (Chambers 1999), NumPy (van der Walt et al. 2011), Pandas (McKinney 2010), PyMC3 (Salvatier et al. 2016), SciPy (Oliphant 2007), stardate (Angus et al. 2019a, 2019b), STARRY (Luger et al. 2018; Agol et al. 2020), Tapir (Jensen 2013), TRANSITFIT5 (Rowe et al. 2015; Rowe 2016), Theano (Theano Development Team 2016), TTVFast (Deck et al. 2014), TTV2Fast2Furious (Hadden et al. 2019), vespa (Morton 2012, 2015)

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