K2-295 b and K2-237 b: Two Transiting Hot Jupiters
ACTA ASTRONOMICA 69:2 (2019) 135-158
Simulating radial velocity observations of trappist-1 with SPIRou
Monthly notices of the Royal Astronomical Society 488 5144
Abstract:
We simulate a radial velocity (RV) follow-up of the TRAPPIST-1 system, a faithful representative of M dwarfs hosting transiting Earth-sized exoplanets to be observed with SPIRou in the months to come. We generate an RV curve containing the signature of the seven transiting TRAPPIST-1 planets and a realistic stellar activity curve statistically compatible with the light curve obtained with the K2 mission. We find a ±5 m s-1 stellar activity signal comparable in amplitude with the planet signal. Using various sampling schemes and white noise levels, we create time-series from which we estimate the masses of the seven planets. We find that the precision on the mass estimates is dominated by (i) the white noise level for planets c, f, and e and (ii) the stellar activity signal for planets b, d, and h. In particular, the activity signal completely outshines the RV signatures of planets d and h that remain undetected regardless of the RV curve sampling and level of white noise in the data set. We find that an RV follow-up of TRAPPIST-1 using SPIRou alone would likely result in an insufficient coverage of the rapidly evolving activity signal of the star, especially with bright-time observations only, making statistical methods such as Gaussian Process Regression hardly capable of firmly detecting planet f and accurately recovering the mass of planet g. In contrast, we show that using bi-site observations with good longitudinal complementary would allow for a more accurate filtering of the stellar activity RV signal.
Three-dimensional Circulation Driving Chemical Disequilibrium in WASP-43b
The Astrophysical Journal American Astronomical Society 869:2 (2018) 107
Wave-mean flow interactions in the atmospheric circulation of tidally locked planets
Astrophysical Journal IOP Publishing 869:1 (2018)
Abstract:
We use a linear shallow-water model to investigate the global circulation of the atmospheres of tidally locked planets. Simulations, observations, and simple models show that if these planets are sufficiently rapidly rotating, their atmospheres have an eastward equatorial jet and a hot-spot east of the substellar point. We linearize the shallow-water model about this eastward flow and its associated geostrophic height perturbation. The forced solutions of this system show that the shear flow explains the form of the global circulation, particularly the hot-spot shift and the positions of the cold standing waves on the night-side. We suggest that the eastward hot-spot shift in observations and 3D simulations of these atmospheres is caused by the zonal flow Doppler-shifting the stationary wave response eastwards, summed with the geostrophic height perturbation from the flow itself. This differs from other studies which explained the hot-spot shift as pure advection of heat from air flowing eastward from the substellar point, or as equatorial waves travelling eastwards. We compare our solutions to simulations in our climate model Exo-FMS and show that they matched the position of the eastward-shifted hot-spot, and the global wind pattern. We discuss how planetary properties affect the global circulation, and how they change observables such as the hot-spot shift or day-night contrast. We conclude that the wave-mean flow interaction be tween the stationary planetary waves and the equatorial jet is a vital part of the equilibrium circulation on tidally locked planets.Extreme-ultraviolet Radiation from A-stars: Implications for Ultra-hot Jupiters
The Astrophysical Journal Letters American Astronomical Society 868:2 (2018) l30