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Title: Planets and X-rays: a radiation diet
Authors: J. Sanz-Forcada, I. Ribas, G. Micela, A. Pollock, D. Garcia-Alvarez, E. Solano, C. Eiroa

According to theory, high energy emission from the coronae of cool stars can severely erode the atmosphere of orbiting planets. To test the long term effects of the erosion we study a large sample of planet-hosting stars observed in X-rays. The results reveal that massive planets (Mp sin i > 1.5 Mj) may survive only if exposed to low accumulated coronal radiation. The planet HD 209458 b might have lost more than 1 Mj already, and other cases, like tau Boo b, could be losing mass at a rate of 3.4 Earth masses per Gyr. The strongest erosive effects would take place during the first stages of the stellar life, when the faster rotation generates more energetic coronal radiation. The planets with higher density seem to resist better the radiation effects, as foreseen by models. Current models need to be improved to explain the observed distribution of planetary masses with the coronal radiation received.

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Title: The upper atmosphere of the exoplanet HD209458b revealed by the sodium D lines: Temperature-pressure profile, ionisation layer, and thermosphere
Authors: A. Vidal-Madjar, D.K. Sing, A. Lecavelier des Etangs, R. Ferlet, J.-M. Desert, G. Hebrard, I. Boisse, D. Ehrenreich, C. Moutou

A complete reassessment of the HST observations of the transits of the extrasolar planet HD209458b has provided a transmission spectrum of the atmosphere over a wide range of wavelengths. Analysis of the NaI absorption line profile has already shown that the sodium abundance has to drop by at least a factor of ten above a critical altitude. Here we analyse the profile in the deep core of the NaI doublet line from HST and high-resolution ground-based spectra to further constrain the vertical structure of the HD209458b atmosphere. With a wavelength-dependent cross section that spans more than 5 orders of magnitude, we use the absorption signature of the NaI doublet as an atmospheric probe. The NaI transmission features are shown to sample the atmosphere of HD209458b over an altitude range of more than 6500km, corresponding to a pressure range of 14 scale heights spanning 1 millibar to 1e-9 bar pressures. By comparing the observations with a multi-layer model in which temperature is a free parameter at the resolution of the atmospheric scale height, we constrain the temperature vertical profile and variations in the Na abundance in the upper part of the atmosphere of HD209458b. We find a rise in temperature above the drop in sodium abundance at the 3mbar level. We also identify an isothermal atmospheric layer at 1500100K spanning almost 6 scale heights in altitude, from 1e-5 to 1e-7 bar. Above this layer, the temperature rises again to 2500(+1500/-1000)K at 1e-9 bar, indicating the presence of a thermosphere. The resulting temperature-pressure (T-P) profile agrees with the Na condensation scenario at the 3 mbar level, with a possible signature of sodium ionisation at higher altitudes, near the 3e-5 bar level. Our T-P profile is found to be in good agreement with the profiles obtained with aeronomical models including hydrodynamic escape.

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HD 209458 b is an extrasolar planet (unofficially referred to as "Osiris") that orbits the Solar analog star HD 209458 in the constellation Pegasus, some 150 light-years from Earth's solar system, with evidence of water vapour.
On November 27, 2001 the Hubble Space Telescope detected sodium, the first planetary atmosphere outside our solar system to be measured.

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Title: Observations of Extrasolar Planet Transit at the Bosscha Observatory
Authors: R.Satyaningsih, B.dermawan, T.Hidayat, S.Siregar, I.Radiman, A.Yamani (Bosscha Observatory and Department of Astronomy, FMIPA, ITB)

Since its first discovery, most extrasolar planets were detected using radial velocity (RV) method. However, the RV method does not provide all parameters required to characterise a planetary system. Recently, Charbonneau et al.(2000) and Brown et al(2001)have shown that the RV planet orbiting HD 209458 can be observed using transit method yielding some additional information. As pointed out by Castellano (2004), this method can be undertaken using small aperture telescopes and inexpensive CCDs. We report here new observations of planetary transit in HD 102195 and HD 209458 performed at the Bosscha Observatory since March 2006. Some preliminary results will be presented

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As if the debate over what is and what is not a planet hasn't gotten confusing enough, Hubble Space Telescope astronomers have now confirmed the existence of a tortured, baked object that could be called a "cometary planet." The gas giant planet, dubbed HD 209458b, is orbiting so close to its star that its heated atmosphere is escaping away into space. Now, observations by the new Cosmic Origins Spectrograph (COS) aboard NASA's Hubble suggest that powerful stellar winds are sweeping the castoff material behind the scorched planet and shaping it into a comet-like tail.
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NASA Finds Super Hot Planet With Unique Comet-Like Tail

Astronomers using NASA's Hubble Space Telescope have confirmed the existence of a baked object that could be called a "cometary planet." The gas giant planet, named HD 209458b, is orbiting so close to its star that its heated atmosphere is escaping into space.
Observations taken with Hubble's Cosmic Origins Spectrograph (COS) suggest powerful stellar winds are sweeping the cast-off atmospheric material behind the scorched planet and shaping it into a comet-like tail.

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Astronomers have measured high-speed winds in the atmosphere of a planet orbiting a distant star.
Data on carbon monoxide gas in the atmosphere show that it is streaming at fierce speeds from the planet's hot day side to its cool night side.
Writing in Nature, a team detected longitudinal winds of roughly 2km/s (7,000km/h) in the atmosphere of a "hot Jupiter" planet.

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VLT Detects First Superstorm on Exoplanet

Astronomers have measured a superstorm for the first time in the atmosphere of an exoplanet, the well-studied "hot Jupiter" HD209458b. The very high-precision observations of carbon monoxide gas show that it is streaming at enormous speed from the extremely hot day side to the cooler night side of the planet. The observations also allow another exciting "first" - measuring the orbital speed of the exoplanet itself, providing a direct determination of its mass.
The results appear this week in the journal Nature.

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HD 209458 Trojan Asteroids
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Title: Searching for Trojan Asteroids in the HD 209458 System: Space-based MOST Photometry and Dynamical Modelling
Authors: Reka Moldovan, Jaymie M. Matthews, Brett Gladman, William F. Bottke, David Vokrouhlicky

We have searched Microvariability and Oscillations of STars (MOST) satellite photometry obtained in 2004, 2005, and 2007 of the solar-type star HD 209458 for Trojan asteroid swarms dynamically coupled with the system's transiting "hot Jupiter" HD 209458b. Observations of the presence and nature of asteroids around other stars would provide unique constraints on migration models of exoplanetary systems. Our results set an upper limit on the optical depth of Trojans in the HD 209458 system that can be used to guide current and future searches of similar systems by upcoming missions. Using cross-correlation methods with artificial signals implanted in the data, we find that our detection limit corresponds to a relative Trojan transit depth of 1 x 10^-4, equivalent to ~1 lunar mass of asteroids, assuming power-law Trojan size distributions similar to Jupiter's Trojans in our solar system. We confirm with dynamical interpretations that some asteroids could have migrated inward with the planet to its current orbit at 0.045 AU, and that the Yarkovsky effect is ineffective at eliminating objects of > 1 m in size. However, using numerical models of collisional evolution we find that, due to high relative speeds in this confined Trojan environment, collisions destroy the vast majority of the asteroids in <10 Myr. Our modelling indicates that the best candidates to search for exoTrojan swarms in 1:1 mean resonance orbits with "hot Jupiters" are young systems (ages of about 1 Myr or less). Years of Kepler satellite monitoring of such a system could detect an asteroid swarm with a predicted transit depth of 3 x 10^-7.

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