Near-Infrared Detection and Characterization of the Exoplanet HD 95086 b with the Gemini Planet Imager

HD 95086 is an intermediate-mass debris-disk-bearing star. VLT/NaCo $3.8 \mu m$ observations revealed it hosts a $5\pm2 \mathrm{M}_{Jup}$ companion (HD 95086 b) at $\simeq 56$ AU. Follow-up observations at 1.66 and 2.18 $\mu m$ yielded a null detection, suggesting extremely red colors for the planet and the need for deeper direct-imaging data. In this Letter, we report H- ($1.7 \mu m$) and $\mathrm{K}_1$- ($2.05 \mu m$) band detections of HD 95086 b from Gemini Planet Imager (GPI) commissioning observations taken by the GPI team. The planet position in both spectral channels is consistent with the NaCo measurements and we confirm it to be comoving. Our photometry yields colors of H-L'= $3.6\pm 1.0$ mag and K$_1$-L'=$2.4\pm 0.7$ mag, consistent with previously reported 5-$\sigma$ upper limits in H and Ks. The photometry of HD 95086 b best matches that of 2M 1207 b and HR 8799 cde. Comparing its spectral energy distribution with the BT-SETTL and LESIA planet atmospheric models yields T$_{\mathrm{eff}}\sim$600-1500 K and log g$\sim$2.1-4.5. Hot-start evolutionary models yield M=$5\pm2$ M$_{Jup}$. Warm-start models reproduce the combined absolute fluxes of the object for M=4-14 M$_{Jup}$ for a wide range of plausible initial conditions (S$_{init}$=8-13 k$_{B}$/baryon). The color-magnitude diagram location of HD 95086 b and its estimated T$_{\mathrm{eff}}$ and log g suggest that the planet is a peculiar L-T transition object with an enhanced amount of photospheric dust.Comment: 4 pages, 4 figures, 3 tables, accepted on April, 15th, 201

Exoplanetary Monte Carlo radiative transfer with correlated-k - I. Benchmarking transit and emission observables

G.K.H. Lee acknowledges support from the University of Oxford and CSH Bern through the Bernoulli fellowship. G.K.H Lee acknowledges funding from the European community through the ERC project EXOCONDENSE (740963). The participants of the OWL 2018 summer program are thanked for numerous discussions and encouragement on the development of the model. J. Taylor is a Penrose Scholar and would like to thank the Oxford Physics Endowment for Graduates (OXPEG) for funding this research. J-L Baudino acknowledges the support of the UK Science and Technology Facilities Council.Current observational data of exoplanets are providing increasing detail of their 3D atmospheric structures. As characterization efforts expand in scope, the need to develop consistent 3D radiative-transfer methods becomes more pertinent as the complex atmospheric properties of exoplanets are required to be modelled together consistently. We aim to compare the transmission and emission spectra results of a 3D Monte Carlo radiative transfer (MCRT) model to contemporary radiative-transfer suites. We perform several benchmarking tests of an MCRT code, Cloudy Monte Carlo Radiative Transfer (CMCRT), to transmission and emission spectra model output. We add flexibility to the model through the use of k-distribution tables as input opacities. We present a hybrid MCRT and ray tracing methodology for the calculation of transmission spectra with a multiple scattering component. CMCRT compares well to the transmission spectra benchmarks at the 10s of ppm level. Emission spectra benchmarks are consistent to within 10 per cent of the 1D models. We suggest that differences in the benchmark results are likely caused by geometric effects between plane-parallel and spherical models. In a practical application, we post-process a cloudy 3D HD 189733b GCM model and compare to available observational data. Our results suggest the core methodology and algorithms of CMCRT produce consistent results to contemporary radiative transfer suites. 3D MCRT methods are highly suitable for detailed post-processing of cloudy and non-cloudy 1D and 3D exoplanet atmosphere simulations in instances where atmospheric inhomogeneities, significant limb effects/geometry or multiple scattering components are important considerations.Publisher PDFPeer reviewe

Analyse des données photométriques et spectroscopiques infrarouges d'exoplanètes obtenues avec l'instrument SPHERE au VLT

Since 2003 direct imaging of exoplanets allows us to obtain spectroscopic and photometric data to characterize their atmospheres. First, our goal was to develop a simple tool to interpret data from SPHERE and GPI to derive planetary physical parameters. We developed a model of young giant exoplanet (called Exo-REM for Exoplanet Radiative-convective Equilibrium Model). Input parameters are surface gravity g, effective temperature (Teff) and an elemental composition. Opacity sources include the H2 –He collision-induced absorption and atomic and molecular lines from eight compounds (including CH4 updated with the Exomol linelist). We consider clouds of iron and silicates without scattering. I have used Exo-REM to analyse photometric and spectral observations of HD 95086 b, beta Pictoris b, kappa Andromedae B, HR 8799 b, c, d, e, GJ 758 B. I finally investigated the presicion to which the above parameters can be constrained from SPHERE measurement.Depuis 2003 l’imagerie directe d’exoplanètes a permis d’obtenir des informations spectroscopiques et photométriques pour caractériser l’atmosphère de ces planètes géantes. Notre but a été tout d’abord de développer un outil simple pour interpréter les observations venant de SPHERE (Spectro-Polarimetric-High-contrast Exoplanet REsearch) au VLT et GPI (Gemini Planet Imager) au Gemini Sud pour déterminer les paramètres physiques des planètes. Nous avons développé un modèle d’exoplanètes géantes jeunes (nommés Exo-REM pour Exoplanet Radiative-convective Equilibriul Model). Les paramètres d’entrée du modèle sont la gravité de surface g, la température effective (Teff) et la composition élémentaire. Les sources d’opacité comprennent l’absorption par le continuum induit par collisions H2 –He et les raies atomiques et moléculaires de 8 corps différents (incluant la liste de raies du méthane d’Exomol). Les absorptions par des nuages de fer et de silicates sont aussi prises en compte sans diffusion. J’ai utilisé Exo-REM avec des observations photométriques et spectroscopiques des planètes naines et brunes HD 95086 b, beta Pictoris b, kappa Andromedae B, HR 8799 b, c, d, e, GJ 758 B. J’ai enfin étudié avec quelle précision pouvait-on dériver les paramètres physiques des planètes à partir de différents jeux d’observations, photométriques et spectroscopiques dans le cadre de SPHERE

Characterising the HR8799 exoplanets with SPHERE using forward models and retrieval

The characterisation of the exoplanets evolved recently thanks to the development of the second generation of direct imaging instruments, especially SPHERE. The resolution and wavelength range available now gives access to an increase in accuracy and in the number of physical parameters that can be constrained. We study the HR8799 system. This system can be seen as a young analogue of the Solar system, with four giant planets placed between two discs. It was one of the first targets of SPHERE. We use a set of observations of HR8799 including photometry by IRDIS for the planets b,c,d and e, and spectroscopy by IFS for d and e. We first show how a forward model (Exo-REM) may be used to obtain the physical parameters of the target. Then we use the results of this first approach as an a priori for the retrieval code (NEMESIS) on the same dataset. We also apply a Nested Sampling version of NEMESIS complementary to the more traditional Optimal Estimation mode. We compare the results of the various approaches highlighting the advantages of each. We give the resulting physical parameters constrained by these approaches to show what SPHERE can determine alone in terms of exoplanet characterisation

A radiative-convective equilibrium model for young giant exoplanets: Applications to beta pictoris b data.

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Beginning a new chapter in the characterization of directly imaged exoplanets: the science of MIRI

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A radiative-convective equilibrium model for young giant exoplanets: Application to beta Pictoris b

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A radiative-convective equilibrium model for young giant exoplanets: Applications to beta pictoris b data.

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A radiative-convective equilibrium model for young giant exoplanets: Applications to beta pictoris b data.

International audienc

Beginning a new chapter in the characterization of directly imaged exoplanets: the science of MIRI

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