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EPIC 246851721 b: A Tropical Jupiter Transiting a Rapidly Rotating Star in a Well-aligned Orbit

Yu, Liang and Zhou, George and Rodriguez, Joseph E. and Huang, Chelsea X. and Vanderburg, Andrew and Quinn, Samuel N. and Gaudi, B. Scott and Beichman, Charles A. and Berlind, Perry and Bieryla, Allyson and Calkins, Michael L. and Ciardi, David R. and Crossfield, Ian J. M. and Eastman, Jason D. and Esquerdo, Gilbert A. and Latham, David W. and Stassun, Keivan G. and Villanueva, Steven, Jr. (2018) EPIC 246851721 b: A Tropical Jupiter Transiting a Rapidly Rotating Star in a Well-aligned Orbit. Astronomical Journal, 156 (6). Art. No. 250. ISSN 1538-3881.

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We report the discovery of EPIC 246851721 b, a "tropical" Jupiter in a 6.18-day orbit around the bright (V=11.439) star EPIC 246851721 (TYC 1283-739-1). We present a detailed analysis of the system using K2 and ground-based photometry, radial velocities, Doppler tomography and adaptive optics imaging. From our global models, we infer that the host star is a rapidly rotating (vsini=74.92 km s^(−1)) F dwarf with T_(eff) = 6202 K, R⋆ = 1.586 R⊙ and M⋆ = 1.317 M⊙. EPIC 246851721 b has a radius of 1.051 ± 0.044 R_J, and a mass of 3.0^(+1.1)_(−1.2)M_J . Doppler tomography reveals an aligned spin-orbit geometry, with a projected obliquity of −1.47∘^(+0.87)_(−0.86), making EPIC 246851721 the fourth hottest star to host a Jovian planet with P > 5 days and a known obliquity. Using quasi-periodic signatures in its light curve that appear to be spot modulations, we estimate the star's rotation period, and thereby infer the true obliquity of the system to be 3.∘^(+3.7)_(−1.8). We argue that this near-zero obliquity is likely to be primordial rather than a result of tidal damping. The host star also has a bound stellar companion, a 0.4 M⊙ M dwarf at a projected separation of 2100 AU, but the companion is likely incapable of emplacing EPIC 246851721 b in its current orbit via high eccentricity Kozai-Lidov migration.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Yu, Liang0000-0003-1667-5427
Zhou, George0000-0002-4891-3517
Rodriguez, Joseph E.0000-0001-8812-0565
Huang, Chelsea X.0000-0003-0918-7484
Vanderburg, Andrew0000-0001-7246-5438
Quinn, Samuel N.0000-0002-8964-8377
Gaudi, B. Scott0000-0003-0395-9869
Beichman, Charles A.0000-0002-5627-5471
Bieryla, Allyson0000-0001-6637-5401
Calkins, Michael L.0000-0002-2830-5661
Ciardi, David R.0000-0002-5741-3047
Crossfield, Ian J. M.0000-0002-1835-1891
Eastman, Jason D.0000-0003-3773-5142
Esquerdo, Gilbert A.0000-0002-9789-5474
Latham, David W.0000-0001-9911-7388
Stassun, Keivan G.0000-0002-3481-9052
Villanueva, Steven, Jr.0000-0001-6213-8804
Additional Information:© 2018 The American Astronomical Society. Received 2018 July 25; revised 2018 September 25; accepted 2018 September 26; published 2018 November 7. We thank Elisabeth Newton and Jennifer Burt for helpful discussions on this manuscript. This research has made use of NASA's Astrophysics Data System, the Exoplanet Follow-up Observing Program (ExoFOP), and 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 National Geographic Society-Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Oschin Schmidt Telescope is operated by the California Institute of Technology and Palomar Observatory. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. 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. Work by G.Z. is provided by NASA through Hubble Fellowship grant HST-HF2-51402.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. Work by C.H. is supported by the Juan Carlos Torres Fellowship. I.J.M.C. acknowledges support from NSF through grant AST-1824644. Work performed by J.E.R. is supported by the Harvard Future Faculty Leaders Postdoctoral fellowship. Facilities: Kepler/K2 - , FLWO:1.5m (TRES) - Fred Lawrence Whipple Observatory's 1.5 meter Telescope, Keck II (NIRC2) - , Magellan:Clay (MIKE) - Magellan II Landon Clay Telescope.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Geographic SocietyUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51402.001-A
Juan Carlos Torres FellowshipUNSPECIFIED
Harvard UniversityUNSPECIFIED
Subject Keywords:planetary systems – planets and satellites: detection – stars: individual (EPIC 246851721)
Issue or Number:6
Record Number:CaltechAUTHORS:20181107-090534578
Persistent URL:
Official Citation:Liang Yu et al 2018 AJ 156 250
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90697
Deposited By: Tony Diaz
Deposited On:07 Nov 2018 17:47
Last Modified:11 Oct 2019 19:45

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