Discovery and characterization of WASP-6b, an inflated sub-Jupiter mass planet transiting a solar-type star

Gillon, M.; Anderson, D. R.; Triaud, A. H. M. J.; Hellier, C.; Maxted, P. F. L.; Pollaco, D.; Queloz, D.; Smalley, B.; West, R. G.; Wilson, David M.; Bentley, S. J.; Cameron, A. Collier; Enoch, B.; Hebb, Leslie; Horne, K.; Irwin, Jonathan; Joshi, Y. C.; Lister, Tim; Mayor, M.; Pepe, F.; Parley, N.; Ségransan, D.; Udry, S.; Wheatley, P. J.

doi:10.1051/0004-6361/200911749

Cited by 76 publications

(65 citation statements)

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“…We fixed the eccentricities of many of these planets to zero: WASP-6b, WASP-12b, WASP-22b, WASP-28b and WASP-32b were reported to have eccentricities of 0.05 (Gillon et al 2009), 0.02 (Hebb et al 2009), 0.02 (Maxted et al 2010), 0.05 Table 2. Jupiter-mass transiting planets used in the analysis of radii.…”

Section: Discussionmentioning

confidence: 99%

Factors affecting the radii of close-in transiting exoplanets

Enoch

Cameron

Horne

2012

A&A

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129

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Context. The radius of an exoplanet may be affected by various factors, including irradiation received from the host star, the mass of the planet and its heavy element content. A significant number of transiting exoplanets have now been discovered for which the mass, radius, semi-major axis, host star metallicity and stellar effective temperature are known. Aims. We use multivariate regression models to determine the power-law dependence of planetary radius on planetary equilibrium temperature T eq , planetary mass M p , stellar metallicity [Fe/H], orbital semi-major axis a, and tidal heating rate H tidal , for 119 transiting planets in three distinct mass regimes. Methods. We fit models initially to all 119 planets, resulting in fairly high scatter between fitted and observed radii, and subsequently to three subsets of these planets: Saturn-mass planets, Jupiter-mass planets, and high-mass planets. Results. We find models for each subset that fit the observed planetary radii well and show the importance of the various environmental parameters on each subset. Conclusions. We determine that heating leads to larger planet radii, as expected, increasing mass leads to increased or decreased radii of low-mass (<0.5 R J ) and high-mass (>2.0 R J ) planets, respectively (with no mass effect on Jupiter-mass planets), and increased host-star metallicity leads to smaller planetary radii, indicating a relationship between host-star metallicity and planet heavy element content. For Saturn-mass planets, a good fit to the radii may be obtained from log(R p /R J ) = -0.077 + 0.450 log(M p /M J ) -0.314 [Fe/H] + 0.671 log(a/AU) + 0.398 log(T eq /K). The radii of Jupiter-mass planets may be fit by log(R p /R J ) = −2.217 + 0.856 log(T eq /K) + 0.291 log(a/AU). High-mass planets' radii are best fit by log(R p /R J ) = -1.067 + 0.380 log(T eq /K) -0.093 log(M p /M J ) -0.057 [Fe/H] + 0.019 log(H tidal /1 × 10 20 ). These equations produce a very good fit to the observed radii, with a mean absolute difference between fitted and observed radius of 0.11 R J , compared to the mean reported uncertainty in observed radius of 0.07 R J . A clear distinction is seen between the core-dominated Saturn-mass (0.1-0.5 M J ) planets, whose radii are determined almost exclusively by their mass and heavy element content, and the gaseous envelope-dominated Jupiter-mass (0.5-2.0 M J ) planets, whose radii increase strongly with irradiating flux, partially offset by a power-law dependence on orbital separation.

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Section: Discussionmentioning

confidence: 99%

Factors affecting the radii of close-in transiting exoplanets

Enoch

Cameron

Horne

2012

A&A

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129

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“…4b,5b,6b,8b and 15b. The results for WASP-6b are presented separately by Gillon et al (2009a) and for WASP-8b by Queloz et al (2010). Two targets were added in separate proposals.…”

Section: The Observationsmentioning

confidence: 99%

Spin-orbit angle measurements for six southern transiting planets

Triaud

Cameron

Queloz

et al. 2010

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Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (>2 M J ). Aims. Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long term radial velocity variability indicating the presence of other bodies in the system. Methods. For transiting planets, the Rossiter-McLaughlin effect allows the measurement of the sky-projected angle β between the stellar rotation axis and a planet's orbital axis. Using the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six transiting hot Jupiters found by the WASP consortium. We combine these with long term radial velocity measurements obtained with CORALIE. We used a combined analysis of photometry and radial velocities, fitting model parameters with the Markov Chain Monte Carlo method. After obtaining β we attempt to statistically determine the distribution of the real spin-orbit angle ψ. Results. We found that three of our targets have β above 90 • : WASP-2b: β = 153 • +11 −15 , WASP-15b: β = 139.6 • +5.2 −4.3 and WASP17b: β = 148.5 • +5.1 −4.2 ; the other three (WASP-4b, WASP-5b and WASP-18b) have angles compatible with 0 • . We find no dependence between the misaligned angle and planet mass nor with any other planetary parameter. All six orbits are close to circular, with only one firm detection of eccentricity e = 0.00848 +0.00085 −0.00095 in WASP-18b. No long-term radial acceleration was detected for any of the targets. Combining all previous 20 measurements of β and our six and transforming them into a distribution of ψ we find that between about 45 and 85% of hot Jupiters have ψ > 30 • . Conclusions. Most hot Jupiters are misaligned, with a large variety of spin-orbit angles. We find observations and predictions using the Kozai mechanism match well. If these observational facts are confirmed in the future, we may then conclude that most hot Jupiters are formed from a dynamical and tidal origin without the necessity to use type I or II migration. At present, standard disc migration cannot explain the observations without invoking at least another additional process.

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“…Gillon et al 2009, Fortney et al 2011, Faedi et al 2011; one extreme case is CoRoT2b with a radius inflated by about 30 % (Guillot & Havel (2011)). This hot-Jupiter orbits the young, solar-type, very active star CoRoT-2A, which was observed (in the optical) by the CoRoT satellite for half a year (Alonso et al 2008).…”

Section: Do Starspots Inflate the Exoplanet Corot-2b?mentioning

confidence: 99%

Occultation Spectrophotometry of Extrasolar Planets with SOFIA

et al. 2012

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Abstract. The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA), a 2.5-meter infrared telescope on board a Boeing 747-SP, will conduct 0.3 -1,600 μm photometric, spectroscopic, and imaging observations from altitudes as high as 45,000 ft., where the average atmospheric transmission is greater than 80 percent. SOFIA's first light cameras and spectrometers, as well as future generations of instruments, will make important contributions to the characterization of the physical properties of exoplanets. Our analysis shows that optical and near-infrared photometric and spectrophotometric follow-up observations during planetary transits and eclipses will be feasible with SOFIA's instrumentation, in particular the HIPO-FLITECAM optical/NIR instruments. The airborne-based platform has unique advantages in comparison to ground-and space-based observatories in this field of research which we will outline here. Furthermore we will present two exemplary science cases, that will be conducted in SOFIA's cycle 1.

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Discovery and characterization of WASP-6b, an inflated sub-Jupiter mass planet transiting a solar-type star

Cited by 76 publications

References 66 publications

Factors affecting the radii of close-in transiting exoplanets

Factors affecting the radii of close-in transiting exoplanets

Spin-orbit angle measurements for six southern transiting planets

Occultation Spectrophotometry of Extrasolar Planets with SOFIA

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