The thermal emission of the exoplanet WASP-3b

We report the detection of thermal emission from the transiting hot Jupiter WASP-3b at 3.6, 4.5 and 8.0 μm using the Spitzer Space Telescope. We obtain planet-to-star flux ratios of 0.209+0.040-0.028 , 0.282 ± 0.012 and 0.328+0.086-0.055 per cent at these wavelengths, respectively, implying infrared brightness temperatures of T3.6μm = 2280+280-150 K, T4.5μm = 2400 ± 80K and T8.0μm = 2210+390-250 K. We find that WASP-3b falls into an emerging class of highly irradiated planets whose measured temperatures suggest that the planets are dark and redistribute heat around the planet inefficiently. The latter is similarly concluded from 1D atmospheric model comparisons, which also favour the presence of an atmospheric temperature inversion. We compare the WASP-3 system to the proposed inversion-activity relation, finding that it hints at a more complex relation than a simple cut-off in activity implied by previous data. Using eclipse timings we also constrain e cos ω to be -0.0006+0.0010-0.0006 , suggesting that the eccentricity of WASP-3b can only be large for a narrow range of ω.</p

WASP-19b : the shortest period transiting exoplanet yet discovered

We report on the discovery of a new extremely short period transiting extrasolar planet, WASP-19b. The planet has mass M-pl = 1.15 +/- 0.08 M-J, radius R-pl = 1.31 +/- 0.06 R-J, and orbital period P = 0.7888399 +/- 0.0000008 days. Through spectroscopic analysis, we determine the host star to be a slightly super-solar metallicity ([M/H] = 0.1 +/- 0.1 dex) G-dwarf with T-eff = 5500 +/- 100 K. In addition, we detect periodic, sinusoidal flux variations in the light curve which are used to derive a rotation period for the star of P-rot = 10.5 +/- 0.2 days. The relatively short stellar rotation period suggests that either WASP-19 is somewhat young (similar to 600 Myr old) or tidal interactions between the two bodies have caused the planet to spiral inward over its lifetime resulting in the spin-up of the star. Due to the detection of the rotation period, this system has the potential to place strong constraints on the stellar tidal quality factor, Q(s)('), if a more precise age is determined

Early Release Science of the exoplanet WASP-39b with JWST NIRCam

International audienceMeasuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs. 1,2) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST’s Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0–4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet’s spectrum. Specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. The otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1–100-times solar (that is, an enrichment of elements heavier than helium relative to the Sun) and a substellar C/O ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (for example, refs. 3,4,) or disequilibrium processes in the upper atmosphere (for example, refs. 5,6)