L and T Dwarf Models and the L to T Transition

Burrows, Adam; Sudarsky, D.; Hubený, I.

doi:10.1086/500293

Cited by 417 publications

(693 citation statements)

References 68 publications

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“…The purpose is to link the photometric errors to the uncertainties in the physical parameters of planetary atmospheres. A related analysis to derive log(g) and T eff was performed by Vigan et al (2010) with the narrowband differential filters of SPHERE combined with AMES-Cond/Dusty (Allard et al 2001(Allard et al , 2003, BT-Settl (Allard et al 2007) and Burrows models (Burrows et al 2006) .…”

Section: Sphere Expected Observationsmentioning

confidence: 99%

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Baudino

Bézard

Boccaletti

et al. 2015

A&A

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Context. Since the end of 2013 a new generation of instruments optimized to image young giant planets around nearby stars directly is becoming available on 8-m class telescopes, both at Very Large Telescope and Gemini in the southern hemisphere. Beyond the achievement of high contrast and the discovery capability, these instruments are designed to obtain photometric and spectral information to characterize the atmospheres of these planets. Aims. We aim to interpret future photometric and spectral measurements from these instruments, in terms of physical parameters of the planets, with an atmospheric model using a minimal number of assumptions and parameters. Methods. We developed the Exoplanet Radiative-convective Equilibrium Model (Exo-REM) to analyze the photometric and spectroscopic data of directly imaged planets. The input parameters are a planet's surface gravity (g), effective temperature (T eff ), and elemental composition. The model predicts the equilibrium temperature profile and mixing ratio profiles of the most important gases. Opacity sources include the H 2 -He collision-induced absorption and molecular lines from eight compounds (including CH 4 updated with the Exomol line list). Absorption by iron and silicate cloud particles is added above the expected condensation levels with a fixed scale height and a given optical depth at some reference wavelength. Scattering was not included at this stage.Results. We applied Exo-REM to photometric and spectral observations of the planet β Pictoris b obtained in a series of near-infrared filters. We derived T eff = 1550 ± 150 K, log(g) = 3.5 ± 1, and radius R = 1.76 ± 0.24 R Jup (2σ error bars from photometric measurements). These values are comparable to those found in the literature, although with more conservative error bars, consistent with the model accuracy. We were able to reproduce, within error bars, the J-and H-band spectra of β Pictoris b. We finally investigated the precision to which the above parameters can be constrained from SPHERE measurements using different sets of near-infrared filters as well as low-resolution spectroscopy.

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Section: Sphere Expected Observationsmentioning

confidence: 99%

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Baudino

Bézard

Boccaletti

et al. 2015

A&A

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“…This is likely due to the presence of remnants of dust clouds, floating around in upper layers, that are not included in the modelled spectra (see Ruiz et al 1997;Ackerman & Marley 2001;Burgasser et al 2002b;Burrows et al 2006;Cooper et al 2003;Helling et al 2008). Cushing et al (2008) have computed the properties of SDSSp J125453.90-012247.4 and 2MASS J05591914-1404488 from the comparison of low and intermediate resolution spectra in the 0.95-14.5 μm wavelength range and synthetic spectra.…”

Section: Modelled and Observed Spectramentioning

confidence: 99%

Physical parameters of T dwarfs derived from high-resolution near-infrared spectra

Burgo

Martín

Osorio

et al. 2009

A&A

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Aims. We determine the effective temperature, surface gravity and projected rotational velocity of nine T dwarfs from the comparison of high-resolution near-infrared spectra and synthetic models, and estimate the mass and age of the objects from state-of-the-art models. Methods. We use the AMES-COND cloudless solar metallicity models provided by the PHOENIX code to match the spectra of nine T-type field dwarfs observed with the near-infrared high-resolution spectrograph NIRSPEC using ten echelle orders to cover part of the J band from 1.147 to 1.347 μm with a resolving power R ∼ 20 000. The projected rotational velocity, effective temperature and surface gravity of the objects are determined based on the minimum root mean square of the differences between the modelled and observed relative fluxes. Estimates of the mass and age of the objects are obtained from effective temperature-surface gravity diagrams, where our results are compared with existing solar metallicity models. Results. The modelled spectra reproduce quite well the observed features for most of the T dwarfs, with effective temperatures in the range of 922-1009 K, and surface gravities between 10 4.1 and 10 4.9 cm s −2 . Our results support the assumption of a dust free atmosphere for T dwarfs later than T5, where dust grains form and then gravitationally sediment into the low atmosphere. The modelled spectra do not accurately mimic some individual very strong lines like the K i doublet at 1.2436 and 1.2525 μm. Our modelled spectra does not match well the observed spectra of the two T dwarfs with earlier spectral types, namely SDSSp J125453.90-012247.4 (T2) and 2MASS J05591914-1404488 (T4.5), which is likely due to the presence of condensate clouds that are not incorporated in the models used here. By comparing our results and their uncertainties to evolutionary models, we estimate masses in the interval ≈5−75 M J for T dwarfs later than T5, which are in good agreement with those found in the literature. We found apparent young ages that are typically between 0.1 and a few Gyr for the same T dwarfs, which is consistent with recent kinematical studies.

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“…In particular, this technique allows us to study the regions beyond the snow line around young stars. Also, taking advantage of the intrinsic luminosity of young giant gaseous planets in the first phases of their evolution, we can infer their masses (see, e.g., evolutionary models by Chabrier et al 2000;Baraffe et al 2002Baraffe et al , 2003Fortney et al 2005;Burrows et al 2006). However, the mass determination is subject to unconstrained physics and unknown initial conditions at very young ages (Marley et al 2007;Spiegel & Burrows 2012) and large discrepancies on the derived mass are expected between the "hot-start" and "warm-start" models.…”

Section: Introductionmentioning

confidence: 99%

Performance of the VLT Planet Finder SPHERE

Zurlo

Vigan

Mesa

et al. 2014

A&A

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Context. The new planet finder for the Very Large Telescope (VLT), the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE), just had its first light in Paranal. A dedicated instrument for the direct detection of planets, SPHERE, is composed of a polametric camera in visible light, the Zurich IMager POLarimeter (ZIMPOL), and two near-infrared sub-systems: the Infra-Red Dual-beam Imager and Spectrograph (IRDIS), a multi-purpose camera for imaging, polarimetry, and long-slit spectroscopy, and the integral field spectrograph (IFS), an integral field spectrograph. Aims. We present the results obtained from the analysis of data taken during the laboratory integration and validation phase, after the injection of synthetic planets. Since no continuous field rotation could be performed in the laboratory, this analysis presents results obtained using reduction techniques that do not use the angular differential imaging (ADI) technique. Methods. To perform the simulations, we used the instrumental point spread function (PSF) and model spectra of L and T-type objects scaled in contrast with respect to the host star. We evaluated the expected error in astrometry and photometry as a function of the signal to noise of companions, after spectral differential imaging (SDI) reduction for IRDIS and spectral deconvolution (SD) or principal component analysis (PCA) data reductions for IFS. Results. We deduced from our analysis, for example, that β Picb, a 12 Myr old planet of ∼10 M Jup and semi-major axis of 9-10 AU, would be detected with IRDIS with a photometric error of 0.16 mag and with a relative astrometric position error of 1.1 mas. With IFS, we could retrieve a spectrum with error bars of about 0.15 mag on each channel and astrometric relative position error of 0.6 mas. For a fainter object such as HR 8799d, a 13 M Jup planet at a distance of 27 AU, IRDIS could obtain a relative astrometric error of 3 mas.

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L and T Dwarf Models and the L to T Transition

Cited by 417 publications

References 68 publications

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Interpreting the photometry and spectroscopy of directly imaged planets: a new atmospheric model applied toβPictoris b and SPHERE observations

Physical parameters of T dwarfs derived from high-resolution near-infrared spectra

Performance of the VLT Planet Finder SPHERE

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