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HAT-P-7
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Title: HAT-P-7: A Retrograde or Polar Orbit, and a Third Body
Authors: Joshua N. Winn, John Asher Johnson, Simon Albrecht, Andrew W. Howard, Geoffrey W. Marcy, Ian J. Crossfield, Matthew J. Holman
(Version v2)

We show that the exoplanet HAT-P-7b has an extremely tilted orbit, with a true angle of at least 86 degrees with respect to its parent star's equatorial plane, and a strong possibility of retrograde motion. We also report evidence for an additional planet or companion star. The evidence for the unparalleled orbit and the third body is based on precise observations of the star's apparent radial velocity. The anomalous radial velocity due to rotation (the Rossiter-McLaughlin effect) was found to be a blueshift during the first half of the transit and a redshift during the second half, an inversion of the usual pattern, implying that the angle between the sky-projected orbital and stellar angular momentum vectors is 182.5 9.4 degrees. The third body is implicated by excess radial-velocity variation of the host star over 2 yr. Some possible explanations for the tilted orbit are a close encounter with another planet, the Kozai effect, and resonant capture by an inward-migrating outer planet.

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RE: HAT-P-7b
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Second backwards planet 'discovered'
Astronomers have discovered a second exoplanet orbiting its star backwards, a day after the first "retrograde" exoplanet was spotted.
Using the Japanese Subaru telescope to observe planet HAT-P-7b, two teams, one led by Joshua Winn of MIT and another led by Norio Narita at the National Astronomical Observatory of Japan, have discovered the second exoplanet.

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L

Posts: 131433
Date:
HAT-P-7
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Title: HAT-P-7: A Retrograde or Polar Orbit, and a Second Planet
Authors: Joshua N. Winn, John Asher Johnson, Simon Albrecht, Andrew W. Howard, Geoffrey W. Marcy, Ian J. Crossfield, Matthew J. Holman

We show that the exoplanet HAT-P-7b has an extremely tilted orbit, with a true angle of at least 86 degrees with respect to its parent star's equatorial plane, and a strong possibility of retrograde motion. We also report evidence for a second planet in a more distant orbit. The evidence for the unparalleled orbit and the additional planet is based on precise observations of the star's apparent radial velocity. The anomalous radial velocity due to rotation (the Rossiter-McLaughlin effect) was found to be a blueshift during the first half of the transit and a redshift during the second half, an inversion of the usual effect, implying that the angle between the sky-projected orbital and stellar angular momentum vectors is 182.5 9.4 deg. The second planet is implicated by excess radial-velocity variation of the host star over 2 yr. Possibly, the second planet tilted the orbit of the inner planet through a close encounter or the Kozai effect.

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Posts: 131433
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RE: HAT-P-7b
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NASA's new exoplanet-hunting Kepler space telescope has detected the atmosphere of a known giant gas planet, demonstrating the telescope's extraordinary scientific capabilities. The discovery will be published Friday in the journal Science.
The observations were collected from a planet called HAT-P-7, known to transit a star located about 1,000 light years from Earth. The planet orbits the star in just 2.2 days and is 26 times closer than Earth is to the sun. Its orbit, combined with a mass somewhat larger than the planet Jupiter, classifies this planet as a "hot Jupiter." It is so close to its star, the planet is as hot as the glowing red heating element on a kitchen stove.

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Title: HAT-P-7b: An Extremely Hot Massive Planet Transiting a Bright Star in the Kepler Field
Authors: A. Pal (1,2), G. A. Bakos (1,3), G. Torres (1), R. W. Noyes (1), D. W. Latham (1), Geza Kovacs (4), G. W. Marcy (5), D. A. Fischer (6), R. P. Butler (7), D. D. Sasselov (1), B. Sipocz (2,1), G. A. Esquerdo (1), Gabor Kovacs (1), R. Stefanik (1), J. Lazar (8), I. Papp (8), P. Sari (8) ((1) CfA, (2) Department of Astronomy, Eotvos Lorand University, (3) NSF Fellow, (4) Konkoly Observatory, (5) Department of Astronomy, UC Berkeley, (6) Department of Physics and Astronomy, San Francisco State University, (7) Department of Terrestrial Magnetism, Carnegie Institute of Washington, (8) Hungarian Astronomical Association)

We report on the latest discovery of the HATNet project; a very hot giant planet orbiting a bright (V = 10.5) star with a small semi-major axis of a = 0.0377 0.0005 AU. Ephemeris for the system is P = 2.2047299 0.0000040 days, mid-transit time E = 2,453,790.2593 0.0010 (BJD). Based on the available spectroscopic data on the host star and photometry of the system, the planet has a mass of Mp = 1.78^{0.08}_{0.05} MJup and radius of Rp = 1.36^{0.20}_{0.09} RJup. The parent star is a slightly evolved F6 star with M = 1.47^{0.08}_{-0.05} Msun,R = 1.84^{0.23}_{0.11} Rsun, Teff = 6350 80 K, and metallicity [Fe/H] = +0.26 0.08. The relatively hot and large host star, combined with the close orbit of the planet, yield a very high planetary irradiance of (4.71^{1.44}_{0.05}) 10^9 erg cm^{-2}s^{-1}, which places the planet near the top of the pM class of irradiated planets as defined by Fortney et al. (2007). If as predicted by Fortney et al. (2007) the planet re-radiates its absorbed energy before distributing it to the night side, the day-side temperature should be about (2730^{150}_{100}) K. Because the host star is quite bright, measurement of the secondary eclipse should be feasible for ground-based telescopes, providing a good opportunity to compare the predictions of current hot Jupiter atmospheric models with the observations. Moreover, the host star falls in the field of the upcoming Kepler mission; hence extensive space-borne follow-up, including not only primary transit and secondary eclipse observations but also asteroseismology, will be possible.

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Planet HAT-P-7b, spotted about a thousand light years away by a network of small telescopes called HATNet, orbits at only 5.6 million kilometres from its star - around one-tenth of the distance between Mercury and our sun.

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