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Published November 20, 2007 | Published
Journal Article Open

HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star


We report the discovery of a massive (M_p = 9.04 ± 0.50 M_J) planet transiting the bright (V = 8.7) F8 star HD 147506, with an orbital period of 5.63341 ± 0.00013 days and an eccentricity of e = 0.520 ± 0.010. From the transit light curve we determine that the radius of the planet is R_p = 0.982^(+0.038)_(-0.105) R_J. HD 147506b (also coined HAT-P-2b) has a mass about 9 times the average mass of previously known transiting exoplanets and a density of ρp ≈ 12 g cm^(-3), greater than that of rocky planets like the Earth. Its mass and radius are marginally consistent with theories of structure of massive giant planets composed of pure H and He, and accounting for them may require a large (≳100 M_⊕) core. The high eccentricity causes a ninefold variation of insolation of the planet between peri- and apastron. Using follow-up photometry, we find that the center of transit is T_(mid) = 2,454,212.8559 ± 0.0007 (HJD) and the transit duration is 0.177 ± 0.002 days.

Additional Information

© 2007 American Astronomical Society. Received 2007 April 29; accepted 2007 July 20. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. 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 Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations fromthismountain. Keck time has been in part granted by NASA. Operation of the HATNet project is funded in part by NASA grant NNG04GN74G. Work by G.Á.B. was supported by NASA through Hubble Fellowship Grant HST-HF-01170.01-A. G. K. wishes to offer thanks for support from the Hungarian Scientific Research Foundation (OTKA) grant K-60750.We acknowledge partial support from the Kepler Mission under NASA Cooperative Agreement NCC2-1390 ( PI: D.W. L.). G. T. acknowledges partial support from NASA Origins grant NNG04LG89G. T. M. thanks the Israel Science Foundation for a support through grant 03/233. D.A. F. is a Cottrell Science Scholar of Research Corporation and acknowledges support from NASA grant NNG05G164G. We would like to thank Joel Hartman (CfA), Gil Esquerdo (CfA), and Ron Dantowitz and Marek Kozubal (Clay Center) for their efforts to observe HAT-P-2b in transit, and Howard Isaacson (San Francisco State University) for obtaining spectra at Lick Observatory. We wish to thank Amit Moran for his help in the observations with the Wise HAT telescope. We owe special thanks to the directors and staff of FLWO, SMA, and the Wise Observatory for supporting the operation of HATNet and WHAT. We would also like to thank the anonymous referee for the useful suggestions that improved this paper.

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August 19, 2023
October 20, 2023