A new model for brown dwarf spectra including accurate unified line
 shape theory for the Na I and K I resonance line profiles

Allard, N. F.; Allard, F.; Hauschildt, P. H.; Kielkopf, John F.; Machin, L.

doi:10.1051/0004-6361:20031299

Cited by 126 publications

(149 citation statements)

References 15 publications

(14 reference statements)

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“…19 Synthetic transit spectra of a hot, gaseous exoplanet in the visible range, assuming a spectral resolution R ∼ 200. The resonance lines are Na at 0.59 μm and K at 0.77 μm (calculated cross sections from Allard et al 2003). Water vapour and methane spectral features are weaker here compared to the IR.…”

Section: A Modelling Of An Exoplanet Transit Spectrum Between 1 and 1mentioning

confidence: 82%

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Spectroscopy of planetary atmospheres in our Galaxy

Tinetti

Encrenaz

Coustenis

2013

Astron Astrophys Rev

128

111

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About 20 years after the discovery of the first extrasolar planet, the number of planets known has grown by three orders of magnitude, and continues to increase at neck breaking pace. For most of these planets we have little information, except for the fact that they exist and possess an address in our Galaxy. For about one third of them, we know how much they weigh, their size and their orbital parameters. For less than 20, we start to have some clues about their atmospheric temperature and composition. How do we make progress from here?We are still far from the completion of a hypothetical Hertzsprung-Russell diagram for planets comparable to what we have for stars, and today we do not even know whether such classification will ever be possible or even meaningful for planetary objects. But one thing is clear: planetary parameters such as mass, radius and temperature alone do not explain the diversity revealed by current observations. The chemical composition of these planets is needed to trace back their formation history and evolution, as happened for the planets in our Solar System. As in situ measurements are and will remain off-limits for exoplanets, to study their chemical composition we will have to rely on remote sensing spectroscopic observations of their gaseous envelopes.

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Section: A Modelling Of An Exoplanet Transit Spectrum Between 1 and 1mentioning

confidence: 82%

“…Theoretical calculations of absorption profiles of Na and K perturbed by H 2 and He at high temperatures have been performed by Allard et al (2003Allard et al ( , 2012. Figure 19 shows a simulated visible spectrum of a gaseous, cloud-free exoplanet at spectral resolution R ∼ 200.…”

Section: The Visible Rangementioning

confidence: 99%

Spectroscopy of planetary atmospheres in our Galaxy

Tinetti

Encrenaz

Coustenis

2013

Astron Astrophys Rev

128

111

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“…T dwarf spectra are also shaped by the collision-induced absorption due to H 2 -H 2 pairs (Borysow 2002;Abel et al 2011) which depresses the 2 μm peak, and by the far wings of very strong Na I and K I lines in the optical (Burrows & Volobuyev 2003;Allard et al 2003) which absorb at wavelengths up to ∼1 μm.…”

Section: T Dwarfsmentioning

confidence: 99%

The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs

Bailey

2014

Publ. Astron. Soc. Aust.

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The last few years has seen a dramatic increase in the number of exoplanets known and in the range of methods for characterising their atmospheric properties. At the same time, new discoveries of increasingly cooler brown dwarfs have pushed down their temperature range which now extends down to Y-dwarfs of < 300 K. Modelling of these atmospheres has required the development of new techniques to deal with the molecular chemistry and clouds in these objects. The atmospheres of brown dwarfs are relatively well understood, but some problems remain, in particular the behavior of clouds at the L/T transition. Observational data for exoplanet atmosphere characterisation is largely limited to giant exoplanets that are hot because they are near to their star (hot Jupiters) or because they are young and still cooling. For these planets there is good evidence for the presence of CO and H2O absorptions in the IR. Sodium absorption is observed in a number of objects. Reflected light measurements show that some giant exoplanets are very dark, indicating a cloud free atmosphere. However, there is also good evidence for clouds and haze in some other planets. It is also well established that some highly irradiated planets have inflated radii, though the mechanism for this inflation is not yet clear. Some other issues in the composition and structure of giant exoplanet atmospheres such as the occurrence of inverted temperature structures, the presence or absence of CO2and CH4, and the occurrence of high C/O ratios are still the subject of investigation and debate.

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“…Major improvements in the theoretical description of pressure broadening have been made compared to the commonly used van der Waals broadening in the impact approximation, see Allard et al (2003) and Burrows & Volobuyev (2003). In this research note, we resume the discussion about the influence of different approximations for the line profiles in synthetic spectra for such cool stellar objects, as introduced in Johnas et al (2006).…”

Section: Introductionmentioning

confidence: 99%

The effects of new $\ion{Na}{i}$ D line profiles in cool atmospheres

Johnas

Hauschildt

Schweitzer

et al. 2007

A&A

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Aims. New Na i D line profiles and their effects on synthetic spectra of cool dwarfs computed with PHOENIX are studied. Sodium is the most abundant alkali in cool dwarf atmospheres and mostly responsible for the shape of the optical spectrum. Methods. In previous work we have pointed out the importance of atomic hydrogen as a perturber. Here, broadening due to collisions with atomic hydrogen as well as fully quantum mechanically calculated profiles for perturbations by helium are introduced for the Na i resonance line profiles. Furthermore, the effects of the new line profiles are compared to already existing line profile calculations.Results. We have calculated a number of "GAIA-cond" class model atmospheres and synthetic spectra for effective temperatures from 1100 K to 3000 K considering a gravity of 4.5. The line formation process has been analyzed with the flux contribution function. Due to changes in atmospheric structure, the effects of the line profiles on the synthetic spectra become larger for smaller effective temperatures. The influence of hydrogen as perturber is visible at higher effective temperatures although at the same time the strength of molecular bands increases. Furthermore, the newly introduced fully quantum mechanically calculated He i broadened profiles change the synthetic spectra by reducing the flux and the depths of the sodium absorption lines.

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A new model for brown dwarf spectra including accurate unified line shape theory for the Na I and K I resonance line profiles

Cited by 126 publications

References 15 publications

Spectroscopy of planetary atmospheres in our Galaxy

Spectroscopy of planetary atmospheres in our Galaxy

The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs

The effects of new $\ion{Na}{i}$ D line profiles in cool atmospheres

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