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RE: Jovian exoplanets
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Title: Water ice lines and the formation of giant moons around super-Jovian planets
Author: René Heller, Ralph Pudritz

Most of the exoplanets with known masses at Earth-like distances to Sun-like stars are heavier than Jupiter, which raises the question of whether such planets are accompanied by detectable, possibly habitable moons. Here we simulate the accretion disks around super-Jovian planets and find that giant moons with masses similar to Mars can form. Our results suggest that the Galilean moons formed during the final stages of accretion onto Jupiter, when the circumjovian disk was sufficiently cool. But in contrast to other studies, we show that Jupiter was still feeding from the circumsolar disk and that its principal moons cannot have formed after the complete photoevaporation of the circumsolar nebula. To counteract the steady loss of moons into the planet due to type I migration, we propose that the water ice line around Jupiter and super-Jovian exoplanets acted as a migration trap for moons. Heat transitions, however, cross the disk during the gap opening within 10^4 yr, which makes them inefficient as moon traps. This indicates a fundamental difference between planet and moon formation. We find that icy moons larger than the smallest known exoplanet can form at about 15 - 30 Jupiter radii around super-Jovian planets. Their size implies detectability by the Kepler and PLATO space telescopes as well as by the European Extremely Large Telescope.

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Gas-Giant Exoplanets
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Gas-Giant Exoplanets Cling Close to Their Parent Stars

Finding extrasolar planets has become so commonplace that it seems astronomers merely have to look up and another world is discovered. However, results from Gemini Observatory's recently completed Planet-Finding Campaign - the deepest, most extensive direct imaging survey to date - show the vast outlying orbital space around many types of stars is largely devoid of gas-giant planets, which apparently tend to dwell close to their parent stars.
"It seems that gas-giant exoplanets are like clinging offspring," says Michael Liu of the University of Hawaii's Institute for Astronomy and leader of the Gemini Planet-Finding Campaign. "Most tend to shun orbital zones far from their parents. In our search, we could have found gas giants beyond orbital distances corresponding to Uranus and Neptune in our own Solar System, but we didn't find any." The Campaign was conducted at the Gemini South telescope in Chile, with funding support for the team from the National Science Foundation and NASA. The Campaign's results, Liu says, will help scientists better understand how gas-giant planets form, as the orbital distances of planets are a key signature that astronomers use to test exoplanet formation theories.

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RE: Jovian exoplanets
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Title: Detection of transiting Jovian exoplanets by Gaia photometry - expected yield
Authors: Yifat Dzigan, Shay Zucker

Several attempts have been made in the past to assess the expected number of exoplanetary transits that the Gaia space mission will detect. In this Letter we use the updated design of Gaia and its expected performance, and apply recent empirical statistical procedures to provide a new assessment. Depending on the extent of the follow-up effort that will be devoted, we expect Gaia to detect a few hundreds to a few thousands transiting exoplanets.

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Title: SOPHIE velocimetry of Kepler transit candidates. V. The three hot Jupiters KOI-135b, KOI-204b and KOI-203b (alias Kepler-17b)
Authors: A. S. Bonomo, G. Hébrard, A. Santerne, N. C. Santos, M. Deleuil, J. Almenara, F. Bouchy, R. F. Díaz, C. Moutou, M. Vanhuysse

We report the discovery of two new transiting hot Jupiters, KOI-135b and KOI-204b, that were previously identified as planetary candidates by Borucki et al. 2011, and, independently of the Kepler team, confirm the planetary nature of Kepler-17b, recently announced by Desert et al. 2011. Radial-velocity measurements, taken with the SOPHIE spectrograph at the OHP, and Kepler photometry (Q1 and Q2 data) were used to derive the orbital, stellar and planetary parameters. KOI-135b and KOI-204b orbit their parent stars in 3.02 and 3.25 days, respectively. They have approximately the same radius, Rp=1.20±0.06 Jupiter radii and 1.24±0.07 Jupiter radii, but different masses Mp=3.23±0.19 Jupiter masses and 1.02±0.07 Jupiter masses. As a consequence, their bulk densities differ by a factor of four, rho_p=2.33±0.36 g.cm^-3 (KOI-135b) and 0.65±0.12 g.cm-3 (KOI-204b). Our SOPHIE spectra of Kepler-17b, used both to measure the radial-velocity variations and determine the atmospheric parameters of the host star, allow us to refine the characterisation of the planetary system. In particular we found the radial-velocity semi-amplitude and the stellar mass to be respectively slightly smaller and larger than Desert et al. These two quantities, however, compensate and lead to a planetary mass fully consistent with Desert et al.: our analysis gives Mp=2.47±0.10 Jupiter masses and Rp=1.33±0.04 Jupiter radii. We found evidence for a younger age of this planetary system, t
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Title: Retired A Stars and Their Companions: Eighteen New Jovian Planets
Authors: John Asher Johnson, Christian Clanton, Andrew W. Howard, Brendan P. Bowler, Gregory W. Henry, Geoffrey W. Marcy, Justin R. Crepp, Michael Endl, William D. Cochran, Phillip J. MacQueen, Jason T. Wright, Howard Isaacson

We report the detection of eighteen Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 < Mstar /Msun < 1.95, radii 2.5 < Rstar/Rsun < 8.7, and metallicities -0.46 < [Fe/H] < +0.30. The planets have minimum masses 0.9 MJup < MP sin i <3 MJup and semimajor axes a > 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5 Msun and provide valuable additional information about the properties of planets around stars more massive than the Sun.

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Binary stars behind puffy exoplanet puzzle

Many Jupiter-like exoplanets are much larger than they ought to be. Now one astronomer thinks he knows why.
Since planets usually form at the same time as stars, astronomers can tell how old and therefore how hot and puffy the gas giants should be. But many of the recently discovered gaseous exoplanets are larger than expected.
Eduardo Martin of the Institute of Astrophysics of the Canary Islands believes this is because the puffy planets formed from the gas and dust ejected when two binary stars merged. This would make the planets much younger than their hosts, which would explain their unusual heat and puffiness. He presented his findings at the American Astronomical Society meeting in Boston last week.

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Title: Evaporation of Jupiter like planets orbiting extreme horizontal branch stars
Authors: Ealeal Bear, Noam Soker (Technion, Israel)

We study the evaporation of planets orbiting close to hot (extreme) horizontal branch (EHB) stars. These planets survived the common envelope phase inside the envelope of the reg giant star progenitor. We find that Jupiter-like planets orbiting within 10Ro from an EHB star suffers a non-negligible mass-loss during their 10^8 yr evolution on the horizontal branch. The evaporated gas is ionised and becomes a source of Balmer lines. Such planets might be detected by the periodic variation of the Doppler shift of the Balmer lines.

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Hot Jovian exoplanets
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Title: Consequences of the Ejection and Disruption of Giant Planets
Authors: James Guillochon (1), Enrico Ramirez-Ruiz (1), Douglas N. C. Lin (1) ((1) UC Santa Cruz)

The discovery of Jupiter-mass planets in close orbits about their parent stars has challenged models of planet formation. Recent observations have shown that a number of these planets have highly inclined, sometimes retrograde orbits about their parent stars, prompting much speculation as to their origin. It is known that migration alone cannot account for the observed population of these misaligned hot Jupiters, which suggests that dynamical processes after the gas disc dissipates play a substantial role in yielding the observed inclination and eccentricity distributions. One particularly promising candidate is planet-planet scattering, which is not very well understood in the non-linear regime of tides. Through three-dimensional hydrodynamical simulations of multi-orbit encounters, we show that planets that are scattered into an orbit about their parent stars with closest approach distance being less than approximately three times the tidal radius are either destroyed or completely ejected from the system. We find that as few as 5 and as many as 18 of the currently known hot Jupiters have a maximum initial apastron for scattering that lies well within the ice line, implying that these planets must have migrated either before or after the scattering event that brought them to their current positions. If stellar tides are unimportant (Q_\ast \gtrsim 10^7), disk migration is required to explain the existence of the hot Jupiters present in these systems. Additionally, we find that the disruption and/or ejection of Jupiter-mass planets deposits a Sun's worth of angular momentum onto the host star. For systems in which planet-planet scattering is common, we predict that planetary hosts have up to a 35% chance of possessing an obliquity relative to the invariable plane of greater than 90 degrees.

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Hot Jupiter Magnetospheres
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Title: Hot Jupiter Magnetospheres
Authors: George B. Trammell, Phil Arras, Zhi-Yun Li (Department of Astronomy, University of Virginia)

The upper atmospheres of close-in gas giant exoplanets are subjected to intense heating/tidal forces from their parent stars. Atomic/ionised hydrogen (H) layers are sufficiently rarefied that magnetic pressure may dominate gas pressure for expected planetary magnetic field strength. We examine the magnetospheric structure using a 3D isothermal magnetohydrodynamic model that includes: a static "dead zone" near the magnetic equator containing magnetically confined gas; a "wind zone" outside the magnetic equator in which thermal pressure gradients and the magneto-centrifugal-tidal effect give rise to transonic outflow; and a region near the poles where sufficiently strong tidal forces may suppress transonic outflow. Using dipole field geometry, we estimate the size of the dead zone to be ~1-10 planetary radii for a range of parameters. To understand appropriate base conditions for the 3D isothermal model, we compute a 1D thermal model in which photoelectric heating from the stellar Lyman continuum is balanced by collisionally-excited Lyman {\alpha} cooling. This 1D model exhibits a H layer with temperatures T=5000-10000K down to pressures of 10-100 nbar. Using the 3D isothermal model, we compute H column densities and Lyman {\alpha} transmission spectra for parameters appropriate to HD 209458b. Line-integrated transit depths of 5-10% can be achieved for the above base conditions. Strong magnetic fields increase the transit signal while decreasing the mass loss, due to higher covering fraction and density of the dead zone. In our model, most of the transit signal arises from magnetically confined gas, some of which may be outside the L1 equipotential. Hence the presence of gas outside the L1 equipotential does not directly imply mass loss. Lastly, we discuss the domain of applicability for the magnetic wind model described in this paper and in the Roche-lobe overflow model.

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Hot Jupiters
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Puffed-up planets are heated like toast

A planet-sized version of an electric toaster could explain why some exoplanets get so large. A related phenomenon could be responsible for keeping in check the gusting winds that form the stripes of Jupiter.
More than 150 planets have been found orbiting closer to their host stars than Mercury is to the sun. Many of these star-hugging gas giants - known as "hot Jupiters" because they can have surface temperatures of 2000 °C or more - have a similar mass to Jupiter but can have up to six times the volume.
Something must be heating the interior of these planets to make them puff up in this way - but what? Radiation from the host star can't be the source, as most of it is reradiated into space from gas at the surface.

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