Transits of Known Planets Orbiting a Naked-Eye Star

Creators: Kane, Stephen R.; Yalçınkaya, Selçuk; Osborn, Hugh P.; Dalba, Paul A.; Nielsen, Louise D.; Vanderburg, Andrew; Mocnik, Teo; Hinkel, Natalie R.; Ostberg, Colby; Esmer, Ekrem Murat; Udry, Stéphane; Fetherolf, Tara; Baştürk, Özgür; Ricker, George R.; Vanderspek, Roland; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Allart, Romain; Bailey, Jeremy; Bean, Jacob L.; Bouchy, Francois; Butler, R. Paul; Campante, Tiago L.; Carter, Brad D.; Daylan, Tansu; Deleuil, Magali; Díaz, Rodrigo F.; Dumusque, Xavier; Ehrenreich, David; Horner, Jonathan; Howard, Andrew W.; Isaacson, Howard; Jones, Hugh R. A.; Kristiansen, Martti H.; Lovis, Christophe; Marcy, Geoffrey W.; Marmier, Maxime; O'Toole, Simon J.; Pepe, Francesco; Ragozzine, Darin; Ségransan, Damien; Tinney, C. G.; Turnbull, Margaret C.; Wittenmyer, Robert A.; Wright, Duncan J.; Wright, Jason T.

Abstract

Some of the most scientifically valuable transiting planets are those that were already known from radial velocity (RV) surveys. This is primarily because their orbits are well characterized and they preferentially orbit bright stars that are the targets of RV surveys. The Transiting Exoplanet Survey Satellite (TESS) provides an opportunity to survey most of the known exoplanet systems in a systematic fashion to detect possible transits of their planets. HD 136352 (Nu2 Lupi) is a naked-eye (V = 5.78) G-type main-sequence star that was discovered to host three planets with orbital periods of 11.6, 27.6, and 108.1 days via RV monitoring with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. We present the detection and characterization of transits for the two inner planets of the HD 136352 system, revealing radii of 1.482^(+0.058)_(−0.056)~R⊕ and 2.608^(+0.078)_(−0.077) R⊕ for planets b and c, respectively. We combine new HARPS observations with RV data from the Keck/High Resolution Echelle Spectrometer and the Anglo-Australian Telescope, along with TESS photometry from Sector 12, to perform a complete analysis of the system parameters. The combined data analysis results in extracted bulk density values of ρ_b = 7.8^(+1.2)_(−1.1) g cm⁻³ and ρ_c = 3.50^(+0.41)_(−0.36) g cm ⁻³ for planets b and c, respectively, thus placing them on either side of the radius valley. The combination of the multitransiting planet system, the bright host star, and the diversity of planetary interiors and atmospheres means this will likely become a cornerstone system for atmospheric and orbital characterization of small worlds.

Additional Information

© 2020 The American Astronomical Society. Received 2020 June 24; revised 2020 July 20; accepted 2020 July 20; published 2020 August 21. The authors would like to thank Jason Eastman for helpful instruction regarding the use of EXOFASTv2, and the anonymous referee whose feedback improved the manuscript. S.R.K. acknowledges support by the National Aeronautics and Space Administration through the TESS Guest Investigator Program (17-TESS17C-1-0004). P.D. acknowledges support from a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903811. S.U., F.B., X.D., D.E, C.L., F.P., M.M., and D.S. acknowledge the financial support of the National Center for Competence in Research, PlanetS, of the Swiss National Science Foundation (SNSF). D.E. acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation program (project Four Aces; grant agreement No. 724427). T.L.C. acknowledges support from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 792848 (PULSATION). H.R.A.J. is supported by UK STFC grant ST/R006598/1. We acknowledge the traditional owners of the land on which the AAT stands, the Gamilaraay people, and pay our respects to elders past and present. 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. Funding for the TESS mission is provided by NASA's Science Mission directorate. 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. 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 paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). The research shown here acknowledges use of the Hypatia Catalog Database, an online compilation of stellar abundance data as described in Hinkel et al. (2014), which was supported by NASA's Nexus for Exoplanet System Science (NExSS) research coordination network and the Vanderbilt Initiative in Data-Intensive Astrophysics (VIDA). This research has 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. The results reported herein benefited from collaborations and/or information exchange within NASA's Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA's Science Mission Directorate. Software: EXOFAST (Eastman et al. 2013, 2019).

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