Winn, Joshua N. and Johnson, John Asher and Howard, Andrew W. and Marcy, Geoffrey W. and Bakos, Gáspár Á. and Hartman, Joel and Torres, Guillermo and Albrecht, Simon and Narita, Norio (2010) The HAT-P-13 Exoplanetary System: Evidence for Spin-Orbit Alignment and a Third Companion. Astrophysical Journal, 718 (1). pp. 575-582. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100818-082810517
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We present new radial velocity (RV) measurements of HAT-P-13, a star with two previously known companions: a transiting giant planet "b" with an orbital period of 3 days and a more massive object "c" on a 1.2 yr, highly eccentric orbit. For this system, dynamical considerations would lead to constraints on planet b's interior structure, if it could be shown that the orbits are coplanar and apsidally locked. By modeling the Rossiter-McLaughlin effect, we show that planet b's orbital angular momentum vector and the stellar spin vector are well aligned on the sky (λ = 1.9 ± 8.6 deg). The refined orbital solution favors a slightly eccentric orbit for planet b (e = 0.0133 ± 0.0041), although it is not clear whether it is apsidally locked with c's orbit (Δω = 36^(+27)_( –36) deg). We find a long-term trend in the star's RV and interpret it as evidence for an additional body "d," which may be another planet or a low-mass star. Predictions are given for the next few inferior conjunctions of c, when transits may happen.
|Additional Information:||© 2010 The American Astronomical Society. Received 2010 March 23; accepted 2010 May 28; published 2010 July 1. We thank Dan Fabrycky for helpful conversations, especially about the dynamical implications of our results. We also thank Debra Fischer and John Brewer for investigating the spectroscopic determination of the stellar rotation rate. We are grateful to Scott Gaudi and Greg Laughlin for comments on the manuscript. J.N.W. gratefully acknowledges support from the NASA Origins program through award NNX09AD36G and the MIT Class of 1942. A.W.H. acknowledges a Townes Postdoctoral Fellowship from the Space Sciences Laboratory at UC Berkeley. G.A.B. was supported by NASA grant NNX08AF23G and an NSF Astronomy & Astrophysics Postdoctoral Fellowship (AST-0702843). G.T. acknowledges partial support from NASA grant NNX09AF59G. S.A. acknowledges the support of the Netherlands Organisation for Scientific Research (NWO). N.N. was supported by a Japan Society for Promotion of Science (JSPS) Fellowship for Research (PD: 20-8141). J.N.W. and N.N. were also supported in part by the National Science Foundation under Grant No. NSF PHY05-51164 (KITP program “The Theory and Observation of Exoplanets” at UCSB). 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, and was made possible by the generous financial support of the W. M. Keck Foundation. We extend special thanks to those of Hawaiian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible. Facilities: Keck:I (HIRES)|
|Subject Keywords:||planets and satellites: dynamical evolution and stability; planets and satellites: formation; planets and satellites: individual (HAT-P-13b, c, d); planets and satellites: interiors; stars: rotation|
|Classification Code:||PACS: 97.20.Jg; 95.85.Kr; 97.10.Kc; 97.82.-j; 97.10.Wn|
|Official Citation:||Joshua N. Winn et al 2010 ApJ 718 575 doi: 10.1088/0004-637X/718/1/575|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||18 Aug 2010 16:46|
|Last Modified:||26 Dec 2012 12:19|
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