Revised Properties and Dynamical History for the HD 17156 System

Creators: Kane, Stephen R.; Hill, Michelle L.; Dalba, Paul A.; Fetherolf, Tara; Henry, Gregory W.; Fajardo-Acosta, Sergio B.; Gnilka, Crystal L.; Howard, Andrew W.; Howell, Steve B.; Isaacson, Howard

Abstract

From the thousands of known exoplanets, those that transit bright host stars provide the greatest accessibility toward detailed system characterization. The first known such planets were generally discovered using the radial-velocity technique, then later found to transit. HD 17156b is particularly notable among these initial discoveries because it diverged from the typical hot-Jupiter population, occupying a 21.2 day eccentric (e = 0.68) orbit, offering preliminary insights into the evolution of planets in extreme orbits. Here we present new data for this system, including ground- and space-based photometry, radial velocities, and speckle imaging, that further constrain the system properties and stellar/planetary multiplicity. These data include photometry from the Transiting Exoplanet Survey Satellite that cover five transits of the known planet. We show that the system does not harbor any additional giant planets interior to 10 au. The lack of stellar companions and the age of the system indicate that the eccentricity of the known planet may have resulted from a previous planet–planet scattering event. We provide the results from dynamical simulations that suggest possible properties of an additional planet that culminated in ejection from the system, leaving a legacy of the observed high eccentricity for HD 17156b.

Additional Information

© 2023. 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. The authors would like to thank Teo Močnik for discussions regarding HD 17156. G.W.H. acknowledges long-term support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. P.D. acknowledges support by a 51 Pegasi b Postdoctoral Fellowship from the Heising-Simons Foundation. T.F. acknowledges support from the University of California President's Postdoctoral Fellowship Program. 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. Observations in the paper also made use of the High-Resolution Imaging instrument 'Alopeke. 'Alopeke 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. 'Alopeke was mounted on the Gemini North telescope of the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). 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), Mercury (Chambers 1999), RadVel (Fulton et al. 2018).

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