Exoplanet atmospheres

Abstract:

The impact of the cloud convective layer of the atmosphere of Venus on the global circulation remains unclear. The recent observations of gravity waves at the top of the cloud by the Venus Express mission provided some answers. These waves are not resolved at the scale of global circulation models (GCM); therefore, we developed an unprecedented 3‐D turbulence‐resolving large‐eddy simulations (LES) Venusian model using the Weather Research and Forecast terrestrial model. The forcing consists of three different heating rates: two radiative ones for solar and infrared and one associated with the adiabatic cooling/warming of the global circulation. The rates are extracted from the Laboratoire de Météorlogie Dynamique Venus GCM using two different cloud models. Thus, we are able to characterize the convection and associated gravity waves in function of latitude and local time. To assess the impact of the global circulation on the convective layer, we used rates from a 1‐D radiative‐convective model. The resolved layer, taking place between 1.0 × 105 and 3.8 × 104 Pa (48–53 km), is organized as polygonal closed cells of about 10 km wide with vertical wind of several meters per second. The convection emits gravity waves both above and below the convective layer leading to temperature perturbations of several tenths of kelvin with vertical wavelength between 1 and 3 km and horizontal wavelength from 1 to 10 km. The thickness of the convective layer and the amplitudes of waves are consistent with observations, though slightly underestimated. The global dynamics heating greatly modify the convective layer.

Abstract:

Jupiter's tropospheric composition is studied using high resolution spatially-resolved 5-mm observation from the CRIRES instrument at the Very Large Telescope. The high resolving power (R=96,000) allows us to spectrally resolve the line shapes of individual molecular species in Jupiter's troposphere and, by aligning the slit north-south along Jupiter's central meridian, we are able to search for any latitudinal variability. Despite the high spectral resolution, we find that there are significant degeneracies between the cloud structure and aerosol scattering properties that complicate the retrievals of tropospheric gaseous abundances and limit conclusions on any belt-zone variability. However, we do find evidence for variability between the equatorial regions of the planet and the polar regions. Arsine (AsH3) and phosphine (PH3) both show an enhancement at high latitudes, while the abundance of germane (GeH4) remains approximately constant. These observations contrast with the theoretical predictions from Wang et al. (2016) and we discuss the possible explanations for this difierence.

Abstract:

Aims. Qatar-1b is a close-orbiting hot Jupiter (R_p ≃ 1.18 R_J, M_p ≃ 1.33 M_J) around a metal-rich K-dwarf, with orbital separation and period of 0.023 AU and 1.42 days. We have observed the secondary eclipse of this exoplanet in the Ks band with the objective of deriving a brightness temperature for the planet and providing further constraints to the orbital configuration of the system.

Methods. We obtained near-infrared photometric data from the ground by using the OMEGA2000 instrument at the 3.5 m telescope at Calar Alto (Spain) in staring mode, with the telescope defocused. We have used principal component analysis (PCA) to identify correlated systematic trends in the data. A Markov chain Monte Carlo analysis was performed to model the correlated systematics and fit for the secondary eclipse of Qatar-1b using a previously developed occultation model. We adopted the prayer bead method to assess the effect of red noise on the derived parameters.

Results. We measured a secondary eclipse depth of 0.196%^{+ 0.071%}_−0.051%, which indicates a brightness temperature in the Ks band for the planet of 1885^{+ 212}_-168 K. We also measured a small deviation in the central phase of the secondary eclipse of −0.0079^{+ 0.0162}_-0.0043, which leads to a value for ecosω of −0.0123^{+ 0.0252}_-0.0067. However, this last result needs to be confirmed with more data.