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The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis

Weiss, Lauren M. and Fabrycky, Daniel C. and Agol, Eric and Mills, Sean M. and Howard, Andrew W. and Isaacson, Howard and Petigura, Erik A. and Fulton, Benjamin and Hirsch, Lea and Sinukoff, Evan (2020) The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis. Astronomical Journal, 159 (5). Art. No. 242. ISSN 1538-3881.

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We present the discovery of Kepler-88 d (P_d = 1403±14 , M sin i_d = 970±50M⊕ = 3.05±0.16M_J, e_d = 0.42±0.04) based on six years of radial velocity (RV) follow-up from the W. M. Keck Observatory High Resolution Echelle Spectrometer spectrograph. Kepler-88 has two previously identified planets. Kepler-88 b (KOI-142.01) transits in the NASA Kepler photometry and has very large transit timing variations (TTVs). Nesvorný et al. performed a dynamical analysis of the TTVs to uniquely identify the orbital period and mass of the perturbing planet (Kepler-88 c), which was later was confirmed with RVs from the Observatoire de Haute-Provence (OHP). To fully explore the architecture of this system, we performed photodynamical modeling on the Kepler photometry combined with the RVs from Keck and OHP and stellar parameters from spectroscopy and Gaia. Planet d is not detectable in the photometry, and long-baseline RVs are needed to ascertain its presence. A photodynamical model simultaneously optimized to fit the RVs and Kepler photometry yields the most precise planet masses and orbital properties yet for b and c: P_b = 10.91647±0.00014days, M_b = 9.5±1.2M⊕, P_c = 22.2649±0.0007 days, and M_c = 214.1±5.3M⊕. The photodynamical solution also finds that planets b and c have low eccentricites and low mutual inclination, are apsidally anti-aligned, and have conjunctions on the same hemisphere of the star. Continued RV follow-up of systems with small planets will improve our understanding of the link between inner planetary system architectures and giant planets.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Weiss, Lauren M.0000-0002-3725-3058
Fabrycky, Daniel C.0000-0003-3750-0183
Agol, Eric0000-0002-0802-9145
Mills, Sean M.0000-0002-4535-6241
Howard, Andrew W.0000-0001-8638-0320
Isaacson, Howard0000-0002-0531-1073
Petigura, Erik A.0000-0003-0967-2893
Fulton, Benjamin0000-0003-3504-5316
Hirsch, Lea0000-0001-8058-7443
Sinukoff, Evan0000-0002-5658-0601
Additional Information:© 2020 The American Astronomical Society. Received 2019 September 5; revised 2020 April 9; accepted 2020 April 10; published 2020 April 29. The authors thank the NASA Kepler Science team for providing the exquisite photometry on which this analysis is based. Without the success of the Kepler mission, the observational follow-up presented here would not have occurred. L.M.W. thanks Molly Kosiarek, Ian Crossfield, Sarah Blunt, Lee Rosenthal, Sam Grunblatt, and Ryan Rubenzahl for contributing to the collection of Keck-HIRES RVs, and Jason Wang, Dan Foreman-Mackey, and Ben Montet for useful discussions. L.M.W. acknowledges the support of Ken and Gloria Levy, the Trottier Family Foundation, the Beatrice Watson Parrent Fellowship, and NASA ADAP Grant 80NSSC19K0597. D.F. acknowledges support from NASA grant NNX17AB93G. E.A. acknowledges support from NSF grant AST-1615315, NASA grants NNX13AF62G, NNA13AA93A, and 80NSSC18K0829. Kepler was competitively selected as the tenth NASA Discovery mission. Funding for this mission is provided by the NASA Science Mission Directorate. We are grateful to the time assignment committees of the University of California, the University of Hawai`i, and NASA for allocating observing time to complete this multi-year project. This work benefited from the 2017 Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a program funded by the Heising-Simons Foundation. This research was partially conducted during the Exostar19 program at the Kavli Institute for Theoretical Physics at UC Santa Barbara, which was supported in part by the National Science Foundation under grant No. NSF PHY-1748958. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: Kepler - The Kepler Mission, Keck:I (HIRES). - Software: RadVel (Fulton et al. 2018), TTVFast (Deck et al. 2014), Phodymm (Mills et al. 2016), Rebound (Rein & Tamayo 2016).
Group:Astronomy Department
Funding AgencyGrant Number
Ken and Gloria LevyUNSPECIFIED
Trottier Family FoundationUNSPECIFIED
Beatrice Watson Parrent FellowshipUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Subject Keywords:Exoplanet astronomy ; Exoplanets ; Exoplanet systems ; Exoplanet detection methods
Issue or Number:5
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Exoplanets (498); Exoplanet systems (484); Exoplanet detection methods (489)
Record Number:CaltechAUTHORS:20191120-105024696
Persistent URL:
Official Citation:Lauren M. Weiss et al 2020 AJ 159 242
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99954
Deposited By: Tony Diaz
Deposited On:20 Nov 2019 19:01
Last Modified:29 Apr 2020 19:53

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