* Astronomy

Title: Observation of the full 12-hour-long transit of the exoplanet HD80606b. Warm-Spitzer photometry and SOPHIE spectroscopy
Authors: G. Hebrard, J.-M. Desert, R.F. Diaz, I. Boisse, F. Bouchy, A. Lecavelier des Etangs, C. Moutou, D. Ehrenreich, L. Arnold, X. Bonfils, X. Delfosse, M. Desort, A. Eggenberger, T. Forveille, J. Gregorio, A.-M. Lagrange, C. Lovis, F. Pepe, C. Perrier, F. Pont, D. Queloz, A. Santerne, N. C. Santos, D. Segransan, D.K. Sing, S. Udry, A. Vidal-Madjar

We present new observations of a transit of the 111-day-period exoplanet HD80606b. Using the Spitzer Space Telescope and its IRAC camera on the post-cryogenic mission, we performed a 19-hour-long photometric observation of HD80606 that covers the full transit of 13-14 January 2010. We complement this photometric data by new spectroscopic observations that we simultaneously performed with SOPHIE at Haute-Provence Observatory. This provides radial velocity measurements of the first half of the transit that was previously uncovered with spectroscopy. This new data set allows the parameters of this singular planetary system to be significantly refined. We obtained a planet-to-star radius ratio R_p/R_* = 0.1001 ±0.0006 that is slightly lower than the one measured from previous ground observations. We detected a feature in the Spitzer light curve that could be due to a stellar spot. We also found a transit timing about 20 minutes earlier than the ephemeris prediction; this could be caused by actual TTVs due to an additional body in the system or by underestimated systematic uncertainties. The sky-projected angle between the spin-axis of HD80606 and the normal to the planetary orbital plane is found to be lambda = 42 ±8 degrees thanks to the fit of the Rossiter-McLaughlin anomaly. This allows scenarios with aligned spin-orbit to be definitively rejected. Over the twenty planetary systems with measured spin-orbit angles, a few of them are misaligned; this is probably the signature of two different evolution scenarios for misaligned and aligned systems, depending if they experienced or not gravitational interaction with a third body. As in the case of HD80606b, most of the planetary systems including a massive planet are tilted; this could be the signature of a separate evolution scenario for massive planets in comparison with Jupiter-mass planets.

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Astronomers detect distant Jupiter-sized planet eclipsing its host star
Taking the help of a telescope in Florida, astronomers have pinned down the extravagantly unusual orbit of HD 80606b, a Jupiter-sized planet nearly 200 light years away, which eclipsed its host star.

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Title: The Transit Ingress and the Tilted Orbit of the Extraordinarily Eccentric Exoplanet HD 80606b
Authors: Joshua N. Winn, Andrew W. Howard, John Asher Johnson, Geoffrey W. Marcy, J. Zachary Gazak, Donn Starkey, Eric B. Ford, Knicole D. Colon, Francisco Reyes, Lisa Nortmann, Stefan Dreizler, Stephen Odewahn, William F. Welsh, Shimonee Kadakia, Robert J. Vanderbei, Elisabeth R. Adams, Matthew Lockhart, Ian J. Crossfield, Jeff A. Valenti, Ronald Dantowitz, Joshua A. Carter

We present the results of a pan-American campaign to observe the 2009 June 5 transit of the exoplanet HD 80606b. We report the first detection of the transit ingress, revealing the transit duration to be 11.64 ±0.25 hr and allowing more robust determinations of the system parameters. Keck spectra obtained at midtransit exhibit an anomalous blueshift, giving definitive evidence that the stellar spin axis and planetary orbital axis are misaligned. The Keck data show that the projected spin-orbit angle is between 32-87 deg with 68.3% confidence and between 14-142 deg with 99.73% confidence. Thus the orbit of this planet is not only highly eccentric (e=0.93), but is also tilted away from the equatorial plane of its parent star. A large tilt had been predicted, based on the idea that the planet's eccentric orbit was caused by the Kozai mechanism. Independently of the theory, it is noteworthy that all 3 exoplanetary systems with known spin-orbit misalignments have massive planets on eccentric orbits, suggesting that those systems migrate differently than lower-mass planets on circular orbits.

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Title: Detection of a transit by the planetary companion of HD 80606
Authors: Stephen J. Fossey, Ingo P. Waldman, David M. Kipping
(Version v2)

We report the detection of a transit egress by the ~ 3.9-Jupiter-mass planet HD 80606b, an object in a highly-eccentric orbit (e ~ 0.93) about its parent star of approximately solar type. The astrophysical reality of the signal of variability in HD 80606 is confirmed by observation with two independent telescope systems, and checks against several reference stars in the field. Differential photometry with respect to the nearby comparison star HD 80607 provides a precise light curve. Modelling of the light curve with a full eccentric-orbit model indicates a planet/star-radius ratio of 0.1057 ±0.0018, corresponding to a planet radius of 1.029 R_J for a solar-radius parent star; and a precise orbital inclination of 89.285 ±0.023 degrees, giving a total transit duration of 12.1 ±0.4 hours. The planet hence joins HD 17156b in a class of highly eccentric transiting planets, in which HD 80606b has both the longest period and most eccentric orbit. The recently reported discovery of a secondary eclipse of HD 80606b by the Spitzer Space Observatory permits a combined analysis with the mid-time of primary transit in which the orbital parameters of the system can be tightly constrained. We derive a transit ephemeris of T_tr = HJD (2454876.344 ±0.011) + (111.4277 ±0.0032) E.

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