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Post Info TOPIC: HAT-P-4b
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RE: HAT-P-4b
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Title: Orbital Orientations of Exoplanets: HAT-P-4b is Prograde and HAT-P-14b is Retrograde
Authors: Joshua N. Winn, Andrew W. Howard, John Asher Johnson, Geoffrey W. Marcy, Howard Isaacson, Avi Shporer, Gaspar A. Bakos, Joel D. Hartman, Matthew J. Holman, Simon Albrecht, Justin R. Crepp, Timothy D. Morton
(Version v2)

We present observations of the Rossiter-McLaughlin effect for two exoplanetary systems, revealing the orientations of their orbits relative to the rotation axes of their parent stars. HAT-P-4b is prograde, with a sky-projected spin-orbit angle of lambda = -4.9 ±11.9 degrees. In contrast, HAT-P-14b is retrograde, with lambda = 189.1 ±5.1 degrees. These results conform with a previously noted pattern among the stellar hosts of close-in giant planets: hotter stars have a wide range of obliquities and cooler stars have low obliquities. This, in turn, suggests that three-body dynamics and tidal dissipation are responsible for the short-period orbits of many exoplanets. In addition, our data revealed a third body in the HAT-P-4 system, which could be a second planet or a companion star.

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Title: HAT-P-4b: A metal-rich low-density transiting hot Jupiter
Authors: G. Kovacs (1), G. A. Bakos (2,3), G. Torres (2), A. Sozzetti (2,4), D. W. Latham (2), R. W. Noyes (2), R. P. Butler (5), G. W. Marcy (6), D. A. Fischer (7), J. M. Fernandez (2), G. Esquerdo (2), D. D. Sasselov (2), R. P. Stefanik (2), A. Pal (8), J. Lazar (9), I. Papp (9), P. Sari (9) ((1) Konkoly Observatory, (2) CfA, (3) Hubble Fellow, (4) INAF - Osservatorio Astronomico di Torino, (5) Department of Terrestrial Magnetism, Carnegie Institute of Washington DC, (6) Department of Astronomy, University of California, Berkeley (7) Department of Physics & Astronomy, San Francisco State University (8) Department of Astronomy, Eötvös Loránd University, (9) Hungarian Astronomical Association)

We describe the discovery of HAT-P-4b, a low-density extrasolar planet transiting BD+36 2593, a V = 11.2 mag slightly evolved metal-rich late F star. The planet's orbital period is 3.056536 ±0.000057 d with a mid-transit epoch of 2,454,245.8154 ± 0.0003 (HJD). Based on high-precision photometric and spectroscopic data, and by using transit light curve modelling, spectrum analysis and evolutionary models, we derive the following planet parameters: Mp= 0.68 ± 0.04 MJ, Rp= 1.27 ± 0.05 RJ, rho = 0.41 ± 0.06 g cm-3 and a = 0.0446 ± 0.0012 AU. Because of its relatively large radius, together with its assumed high metallicity of that of its parent star, this planet adds to the theoretical challenges to explain inflated extrasolar planets.

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