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TrES-2
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Title: A consistent analysis of three years of ground- and space-based photometry of TrES-2
Authors: S. Schröter, J. H. M. M. Schmitt, H. M. Müller

The G0V dwarf TrES-2A, which is transited by a hot Jupiter, is one of the main short-cadence targets of the Kepler telescope and, therefore, among the photometrically best-studied planetary systems known today. Given the near-grazing geometry of the planetary orbit, TrES-2 offers an outstanding opportunity to search for changes in its orbital geometry. Our study focuses on the secular change in orbital inclination reported in previous studies. We present a joint analysis of the first four quarters of Kepler photometry together with the publicly available ground-based data obtained since the discovery of TrES-2b in 2006. We use a common approach based on the latest information regarding the visual companion of TrES-2A and stellar limb darkening to further refine the orbital parameters. We find that the Kepler observations rule out a secular inclination change of previously claimed order as well as variations of the transit timing, however, they also show slight indication for further variability in the inclination which remains marginally significant.

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RE: TrES-2b
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Sternenstaub in weit entfernten Planetensystemen entdeckt

Die Suche nach extrasolaren Planeten - also Planeten auberhalb unseres Sonnensystems - hat Konjunktur. Aktuell sind gut 700 solcher Planeten bekannt, dank raffinierter Observationstechnik steigt diese Zahl kontinuierlich an. Einem Team von Astronomen um Prof. Dr. Alexander Krivov von der Friedrich-Schiller-Universität Jena ist nun eine Aufsehen erregende Entdeckung gelungen: Die Wissenschaftler vom Astrophysikalischen Institut konnten bei zwei Sternen sogenannte Trümmerscheiben nachweisen. Die Trümmerscheiben - englisch Debris discs - sind Uberbleibsel der Planetenentstehung. "Es handelt sich dabei um gewaltige Ansammlungen von Materie-Brocken, die bei Zusammenstöben den Staub erzeugen", sagt Alexander Krivov. Dieser Staub ist für die Astronomen von enormer Bedeutung, weil sich mit seiner Hilfe Rückschlüsse auf die Entstehung der Planeten ziehen lassen. In unserem Sonnensystem befinden sich sogar zwei Trümmerscheiben, der Asteroidengürtel sowie der Kuipergürtel, zu dessen Bestandteilen der Zwergplanet Pluto gehört.
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Darkest exoplanet spotted by astronomers

A dark alien world, blacker than coal, has been spotted by astronomers.
The Jupiter-sized planet is orbiting its star at a distance of just five million km, and is likely to be at a temperature of some 1200C.
The planet may be too hot to support reflective clouds like those we see in our own Solar System, but even that would not explain why it is so dark.

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Detection of visible light from the darkest world

Astronomers have discovered the darkest known exoplanet - a distant, Jupiter-sized gas giant known as TrES-2b. Their measurements show that TrES-2b reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system. The new work appears in a paper in the journal Monthly Notices of the Royal Astronomical Society.
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Title: Analysis of Kepler's short-cadence photometry for TrES-2b
Authors: David M. Kipping, Gáspár Á. Bakos
(Version v3)

We present an analysis of 18 short-cadence (SC) transit lightcurves of TrES-2b using quarter 0 (Q0) and quarter 1 (Q1) from the Kepler Mission. The photometry is of unprecedented precision, 237ppm per minute, allowing for the most accurate determination of the transit parameters yet obtained for this system. Global fits of the transit photometry, radial velocities and known transit times are used to obtain a self-consistent set of refined parameters for this system, including updated stellar and planetary parameters. Special attention is paid to fitting for limb darkening and eccentricity. We place an upper limit on the occultation depth to be <72.9ppm to 3-sigma confidence, indicating TrES-2b has the lowest determined geometric albedo for an exoplanet, of Ag<0.146. We also produce a transit timing analysis using Kepler's short-cadence data and demonstrate exceptional timing precision at the level of a few seconds for each transit event. With 18 fully-sampled transits at such high precision, we are able to produce stringent constraints on the presence of perturbing planets, Trojans and extrasolar moons. We introduce the novel use of control data to identify phasing effects. We also exclude the previously proposed hypotheses of short-period TTV and additional transits but find the hypothesis of long-term inclination change is neither supported nor refuted by our analysis.

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Title: Analysis of Kepler's short-cadence photometry for TrES-2b
Authors: David M. Kipping, Gáspár Á. Bakos

We present an analysis of 18 short-cadence (SC) transit lightcurves of TrES-2b using quarter 0 (Q0) and quarter 1 (Q1) from the Kepler Mission. The photometry is of unprecedented precision, 230 ppm per minute, allowing for the most accurate determination of the transit parameters yet obtained for this system. Global fits of the transit photometry, radial velocities and known transit times are used to obtain a self-consistent set of refined parameters for this system, including updated stellar and planetary parameters. Special attention is paid to fitting for limb darkening and eccentricity. We make a marginal 2-sigma detection of the secondary eclipse of depth (11.4 ±7.8) ppm, indicative of a non-zero but very low albedo contribution.
We also produce the first transit timing analysis using Kepler's short-cadence data and demonstrate exceptional timing precision at the level of a few seconds for each transit event. With 18 fully-sampled transits at such high precision, we are able to produce stringent constraints on the presence of perturbing planets, Trojans and extrasolar moons. Both the TTVs and TDVs show significant peaks in periodogram searches for which the TTV is certainly spurious and the TDV is likely spurious. We also exclude the previously proposed hypotheses of inclination change, short-period TTV and additional transits.

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Title: Multi-band transit observations of the TrES-2b exoplanet
Authors: D. Mislis, S. Schroter, J.H.M.M. Schmitt, O. Cordes, K. Reif
(Version v2)

We present a new data set of transit observations of the TrES-2b exoplanet taken in spring 2009, using the 1.2m Oskar-Luhning telescope (OLT) of Hamburg Observatory and the 2.2m telescope at Calar Alto Observatory using BUSCA (Bonn University Simultaneous CAmera). Both the new OLT data, taken with the same instrumental setup as our data taken in 2008, as well as the simultaneously recorded multicolour BUSCA data confirm the low inclination values reported previously, and in fact suggest that the TrES-2b exoplanet has already passed the first inclination threshold (i_min,1 = 83.417) and is not eclipsing the full stellar surface any longer. Using the multi-band BUSCA data we demonstrate that the multicolour light curves can be consistently fitted with a given set of limb darkening coefficients without the need to adjust these coefficients, and further, we can demonstrate that wavelength dependent stellar radius changes must be small as expected from theory. Our new observations provide further evidence for a change of the orbit inclination of the transiting extrasolar planet TrES-2b reported previously. We examine in detail possible causes for this inclination change and argue that the observed change should be interpreted as nodal regression. While the assumption of an oblate host star requires an unreasonably large second harmonic coefficient, the existence of a third body in the form of an additional planet would provide a very natural explanation for the observed secular orbit change. Given the lack of clearly observed short-term variations of transit timing and our observed secular nodal regression rate, we predict a period between approximately 50 and 100 days for a putative perturbing planet of Jovian mass. Such an object should be detectable with present-day radial velocity (RV) techniques.

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Title: The Prograde Orbit of Exoplanet TrES-2b
Authors: Joshua N. Winn, John Asher Johnson, Norio Narita, Yasushi Suto, Edwin L. Turner, Debra A. Fischer, R. Paul Butler, Steven S. Vogt, Francis T. O'Donovan, B. Scott Gaudi

We monitored the Doppler shift of the G0V star TrES-2 throughout a transit of its giant planet. The anomalous Doppler shift due to stellar rotation (the Rossiter-McLaughlin effect) is discernible in the data, with a signal-to-noise ratio of 2.9, even though the star is a slow rotator. By modelling this effect we find that the planet's trajectory across the face of the star is tilted by -9 +/- 12 degrees relative to the projected stellar equator. With 98% confidence, the orbit is prograde.

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