A Mini-Neptune and a Radius Valley Planet Orbiting the Nearby M2 Dwarf TOI-1266 in Its Venus Zone: Validation with the Habitable-zone Planet Finder

Creators: Stefánsson, Guðmundur; Kopparapu, Ravi; Lin, Andrea; Mahadevan, Suvrath; Cañas, Caleb I.; Kanodia, Shubham; Ninan, Joe P.; Cochran, William D.; Endl, Michael; Hebb, Leslie; Wisniewski, John; Gupta, Arvind; Everett, Mark; Bender, Chad F.; Diddams, Scott A.; Ford, Eric B.; Fredrick, Connor; Halverson, Samuel; Hearty, Fred; Levi, Eric; Maney, Marissa; Metcalf, Andrew J.; Monson, Andrew; Ramsey, Lawrence W.; Robertson, Paul; Roy, Arpita; Schwab, Christian; Terrien, Ryan C.; Wright, Jason T.

Abstract

We report on the validation of two planets orbiting the nearby (36 pc) M2 dwarf TOI-1266 observed by the TESS mission. This system is one of a few M dwarf multiplanet systems with close-in planets where the inner planet is substantially larger than the outer planet. The inner planet is sub-Neptune-sized (R = 2.46 ± 0.08 R_⊕) with an orbital period of 10.9 days, while the outer planet has a radius of 1.67_(-0.11)^(+0.09) R_⊕ and resides in the exoplanet radius valley—the transition region between rocky and gaseous planets. With an orbital period of 18.8 days, the outer planet receives an insolation flux of 2.4 times that of Earth, similar to the insolation of Venus. Using precision near-infrared radial velocities with the Habitable-zone Planet Finder Spectrograph, we place upper mass limits of 15.9 and 6.4 M_⊕ at 95% confidence for the inner and outer planet, respectively. A more precise mass constraint of both planets, achievable with current radial velocity instruments given the host star brightness (V = 12.9, J = 9.7), will yield further insights into the dominant processes sculpting the exoplanet radius valley.

Additional Information

© 2020. The American Astronomical Society. Received 2020 June 18; revised 2020 September 24; accepted 2020 September 25; published 2020 November 13. We thank the anonymous referee for a thoughtful reading of the manuscript and useful suggestions and comments that made for a clearer and stronger manuscript. We thank Josh Winn for useful discussions. This work was partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. This work was supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program through grant 80NSSC18K1114. We acknowledge support from NSF grants AST-1006676, AST-1126413, AST-1310885, AST-1517592, AST-1310875, AST-1910954, AST-1907622, and AST-1909506; the NASA Astrobiology Institute (NAI; NNA09DA76A); and PSARC in our pursuit of precision radial velocities in the NIR. Computations for this research were performed at the Pennsylvania State University's Institute for Computational & Data Sciences (ICDS). These results are based on observations obtained with the Habitable-zone Planet Finder Spectrograph on the Hobby-Eberly Telescope (HET). We thank the resident astronomers and telescope operators at the HET for the skillful execution of our observations with the HPF. The HET is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August Universität Gottingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. The HET collaboration acknowledges support and resources from the Texas Advanced Computing Center. The WIYN Observatory is a joint facility of the University of Wisconsin–Madison, Indiana University, Yale University, the NSF Optical Infrared Research Lab, the University of Missouri, Purdue University, Penn State University, and the University of California at Irvine. Some of the observations in the paper made use of the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI). NESSI was funded by the NASA Exoplanet Exploration Program and the NASA Ames Research Center. NESSI was built at the Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. These results are based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium. We wish to thank the APO 3.5 m telescope operators for their assistance in obtaining these data. Some observations were obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the ZTF project. The ZTF is supported by the NSF under grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin–Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. We acknowledge the use of public TOI release data from pipelines at the TESS Science Office and 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 paper includes data collected by the TESS mission, which are publicly available from the Multimission Archive for Space Telescopes (MAST). Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. This research made use of Lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration, 2018). This research made use of the NASA Exoplanet Archive, 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. Facilities: TESS - , Gaia - , HPF/HET 10 m - , ARCTIC/ARC 3.5 m - , NESSI/WIYN 3.5 m - , Perkin 0.4 m - , ZTF - , ASAS. - Software: AstroImageJ (Collins et al. 2017), astroplan (Morris et al. 2018), astropy (Astropy Collaboration et al. 2013), astroquery (Ginsburg et al. 2018), barycorrpy (Kanodia & Wright 2018), batman (Kreidberg 2015), corner.py (Foreman-Mackey 2016), celerite (Foreman-Mackey et al. 2017), dynesty (Speagle 2020), EXOFASTv2 (Eastman 2017), exoplanet (Foreman-Mackey et al. 2020), forecaster (Chen & Kipping 2017), GALPY (Bovy 2015), GNU Parallel (Tange 2011), HxRGproc (Ninan et al. 2018), iDiffuse (Stefansson et al. 2018b), Jupyter (Kluyver et al. 2016), juliet (Espinoza et al. 2019), matplotlib (Hunter 2007), MRExo (Kanodia et al. 2019), numpy (Van Der Walt et al. 2011), pandas (McKinney 2010), PyMC3 (Salvatier et al. 2016), radvel (Fulton et al. 2018), SERVAL (Zechmeister et al. 2018), starry (Luger et al. 2019), tesscut (Brasseur et al. 2019), transitleastsquares (Hippke & Heller 2019).

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