Publications by Vivien Parmentier


The Transiting Exoplanet Community Early Release Science Program for JWST

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L Kreidberg, N Crouzet, B Benneke, Line, DK Sing, HR Wakeford, HA Knutson, EM-R Kempton, J-M Désert, I Crossfield, NE Batalha, JD Wit, V Parmentier, J Harrington, JI Moses, M Lopez-Morales, MK Alam, J Blecic, G Bruno, AL Carter, JW Chapman, L Decin, D Dragomir, TM Evans, JJ Fortney

The James Webb Space Telescope (JWST) presents the opportunity to transform our understanding of planets and the origins of life by revealing the atmospheric compositions, structures, and dynamics of transiting exoplanets in unprecedented detail. However, the high-precision, time-series observations required for such investigations have unique technical challenges, and prior experience with other facilities indicates that there will be a steep learning curve when JWST becomes operational. In this paper we describe the science objectives and detailed plans of the Transiting Exoplanet Community Early Release Science (ERS) Program, which is a recently approved program for JWST observations early in Cycle 1. The goal of this project, for which the obtained data will have no exclusive access period, is to accelerate the acquisition and diffusion of technical expertise for transiting exoplanet observations with JWST, while also providing a compelling set of representative datasets that will enable immediate scientific breakthroughs. The Transiting Exoplanet Community ERS Program will exercise the time-series modes of all four JWST instruments that have been identified as the consensus highest priorities, observe the full suite of transiting planet characterization geometries (transits, eclipses, and phase curves), and target planets with host stars that span an illustrative range of brightnesses. The observations in this program were defined through an inclusive and transparent process that had participation from JWST instrument experts and international leaders in transiting exoplanet studies. Community engagement in the project will be centered on a two-phase Data Challenge that culminates with the delivery of planetary spectra, time-series instrument performance reports, and open-source data analysis toolkits in time to inform the agenda for Cycle 2 of the JWST mission.


Global Climate and Atmospheric Composition of the Ultra-hot Jupiter WASP-103b from HST and Spitzer Phase Curve Observations

The Astronomical Journal American Astronomical Society 156 (0) 17-17

L Kreidberg, MR Line, V Parmentier, KB Stevenson, T Louden, M Bonnefoy, JK Faherty, GW Henry, MH Williamson, K Stassun, TG Beatty, JL Bean, JJ Fortney, AP Showman, J-M Désert, J Arcangeli


Transitions in the cloud composition of hot Jupiters

The Astrophysical Journal American Astronomical Society (0)

V Parmentier, JJ Fortney, AP Showman, CV Morley, MS Marley

Over a large range of equilibrium temperatures, clouds shape the transmission spectrum of hot Jupiter atmospheres, yet their composition remains unknown. Recent observations show that the Kepler lightcurves of some hot Jupiters are asymmetric: for the hottest planets, the lightcurve peaks before secondary eclipse, whereas for planets cooler than $\sim1900\rm\,K$, it peaks after secondary eclipse. We use the thermal structure from 3D global circulation models to determine the expected cloud distribution and Kepler lightcurves of hot Jupiters. We demonstrate that the change from an optical lightcurve dominated by thermal emission to one dominated by scattering (reflection) naturally explains the observed trend from negative to positive offset. For the cool planets the presence of an asymmetry in the Kepler lightcurve is a telltale sign of the cloud composition, because each cloud species can produce an offset only over a narrow range of effective temperatures. By comparing our models and the observations, we show that the cloud composition of hot Jupiters likely varies with equilibrium temperature. We suggest that a transition occurs between silicate and manganese sulfide clouds at a temperature near $1600\rm\,K$, analogous to the L/T transition on brown dwarfs. The cold trapping of cloud species below the photosphere naturally produces such a transition and predicts similar transitions for other condensates, including TiO. We predict that most hot Jupiters should have cloudy nightsides, that partial cloudiness should be common at the limb and that the dayside hot spot should often be cloud-free.


THE INFLUENCE OF NONUNIFORM CLOUD COVER ON TRANSIT TRANSMISSION SPECTRA

The Astrophysical Journal American Astronomical Society 820 (0) 78-78

MR Line, V Parmentier


The cloudy shape of hot Jupiter thermal phase curves

ArXiv (0)

V Parmentier, AP Showman, JJ Fortney

Hot Jupiters have been predicted to have a strong day/night temperature contrast and a hot spot shifted eastward of the substellar point. This was confirmed by numerous phase curve observations probing the longitudinal brightness variation of the atmosphere. Global circulation models, however, systematically underestimate the phase curve amplitude and overestimate the shift of its maximum. We use a global circulation model including non-grey radiative transfer and realistic gas and cloud opacities to systematically investigate how the atmospheric circulation of hot Jupiters varies with equilibrium temperature from 1000 to 2200K. We show that the heat transport is very efficient for cloudless planets cooler than 1600K and becomes less efficient at higher temperatures. When nightside clouds are present, the day-to-night heat transport becomes extremely inefficient, leading to a good match to the observed low nightside temperatures. The constancy of this low temperature is, however, due to the strong dependence of the radiative timescale with temperature. We further show that nightside clouds increase the phase curve amplitude and decreases the phase curve offset at the same time. This change is very sensitive to the cloud chemical composition and particle size, meaning that the diversity in observed phase curves can be explained by a diversity of nightside cloud properties. Finally, we show that phase curve parameters do not necessarily track the day/night contrast nor the shift of the hot spot on isobars, and propose solutions to to recover the true hot-spot shift and day/night contrast.


A non-grey analytical model for irradiated atmospheres. II: Analytical vs. numerical solutions

Astronomy and Astrophysics EDP Sciences 574 (0) A35-A35

V Parmentier, T Guillot, JJ Fortney, MS Marley

The recent discovery and characterization of the diversity of the atmospheres of exoplanets and brown dwarfs calls for the development of fast and accurate analytical models. We quantify the accuracy of the analytical solution derived in paper I for an irradiated, non-grey atmosphere by comparing it to a state-of-the-art radiative transfer model. Then, using a grid of numerical models, we calibrate the different coefficients of our analytical model for irradiated solar-composition atmospheres of giant exoplanets and brown dwarfs. We show that the so-called Eddington approximation used to solve the angular dependency of the radiation field leads to relative errors of up to 5% on the temperature profile. We show that for realistic non-grey planetary atmospheres, the presence of a convective zone that extends to optical depths smaller than unity can lead to changes in the radiative temperature profile on the order of 20% or more. When the convective zone is located at deeper levels (such as for strongly irradiated hot Jupiters), its effect on the radiative atmosphere is smaller. We show that the temperature inversion induced by a strong absorber in the optical, such as TiO or VO is mainly due to non-grey thermal effects reducing the ability of the upper atmosphere to cool down rather than an enhanced absorption of the stellar light as previously thought. Finally, we provide a functional form for the coefficients of our analytical model for solar-composition giant exoplanets and brown dwarfs. This leads to fully analytical pressure-temperature profiles for irradiated atmospheres with a relative accuracy better than 10% for gravities between 2.5m/s^2 and 250 m/s^2 and effective temperatures between 100 K and 3000 K. This is a great improvement over the commonly used Eddington boundary condition.

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