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Published April 2012 | Published
Journal Article Open

HAT-P-17b,c: A Transiting, Eccentric, Hot Saturn and a Long-period, Cold Jupiter


We report the discovery of HAT-P-17b,c, a multi-planet system with an inner transiting planet in a short-period, eccentric orbit and an outer planet in a 4.4 yr, nearly circular orbit. The inner planet, HAT-P-17b, transits the bright V = 10.54 early K dwarf star GSC 2717-00417, with an orbital period P = 10.338523 ± 0.000009 days, orbital eccentricity e = 0.342 ± 0.006, transit epoch T_c = 2454801.16943 ± 0.00020 (BJD: barycentric Julian dates throughout the paper are calculated from Coordinated Universal Time (UTC)), and transit duration 0.1690 ± 0.0009 days. HAT-P-17b has a mass of 0.534 ± 0.018 M_J and radius of 1.010 ± 0.029 R_J yielding a mean density of 0.64 ± 0.05 g cm^(–3). This planet has a relatively low equilibrium temperature in the range 780-927 K, making it an attractive target for follow-up spectroscopic studies. The outer planet, HAT-P-17c, has a significantly longer orbital period P_2 = 1610 ± 20 days and a minimum mass m_2sini_2 = 1.31^(+0.18)_(–0.15) M_J. The orbital inclination of HAT-P-17c is unknown as transits have not been observed and may not be present. The host star has a mass of 0.86 ± 0.04 M_☉, radius of 0.84 ± 0.02 R_☉, effective temperature 5246 ± 80 K, and metallicity [Fe/H] = 0.00 ± 0.08. HAT-P-17 is the second multi-planet system detected from ground-based transit surveys.

Additional Information

© 2012 American Astronomical Society. Received 2010 August 24; accepted 2011 August 23; published 2012 April 2. Based in part on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO and NASA. We thank E. Agol, H. Knutson, J. Winn, and J. Wright for helpful conversations. HATNet operations have been funded by NASA grants NNG04GN74G, NNX08AF23G, and SAO IR&D grants. A.W.H. gratefully acknowledges support from a Townes Post-doctoral Fellowship at the U. C. Berkeley Space Sciences Laboratory. Work of G. Á. B. and J. Johnson were supported by the Postdoctoral Fellowship of the NSF Astronomy and Astrophysics Program (AST-0702843 and AST-0702821, respectively). G.T. acknowledges partial support from NASA grant NNX09AF59G. We acknowledge partial support also from the Kepler mission under NASA Cooperative Agreement NCC2-1390 (D.W.L.: PI). G.K. thanks the Hungarian Scientific Research Foundation (OTKA) for support through grant K-81373. T.M. acknowledges the Israel Science Foundation (grant 655/07). This research has made use of Keck telescope time granted through NOAO and NASA. We thank Ezra Mashal for his help in operating the Wise-HAT telescope over the past years. We thank the TLC project (M. Holman and J. Winn) for swapping time on the 1.2 m telescope at short notice. This research has made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at exoplanets.org, the SIMBAD database (operated at CDS, Strasbourg, France), and NASA's Astrophysics Data System Bibliographic Services. Finally, the authors wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Mauna Kea we were privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible.

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