F. Allard

École Normale Supérieure de Lyon

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Papers

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Author Order

Document Type

Co-Authors

D. Homeier

Heidelberg University

111

P. H. Hauschildt

Hamburger Fern-Hochschule

I. Baraffe

École Normale Supérieure de Lyon

M. Bonnefoy

Institut de Planétologie et d'Astrophysique de Grenoble

P. H. Hauschildt

Hamburger Fern-Hochschule

G. Chabrier

École Normale Supérieure de Lyon

A. Schweitzer

Universität Hamburg

T. Forveille

Université Grenoble Alpes

G. Chauvin

Université Côte d'Azur

A. S. Rajpurohit

Physical Research Laboratory

Cooperative Institutions

Centre National de la Recherche Scientifique

410

Max Planck Society

197

Max Planck Institute for Astronomy

187

Université Paris Cité

133

Sorbonne Université

130

Observatoire de Paris

126

National Institute for Astrophysics

117

Université Grenoble Alpes

111

Laboratoire d’études spatiales et d’instrumentation en astrophysique

109

Institut de Planétologie et d'Astrophysique de Grenoble

109

Author Statistics

Papers

Citation

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Research Field

Low‐Temperature Opacities

The Astrophysical Journal (2005)

Jason W. Ferguson D. R. Alexander F. Allard Travis Barman J. Bodnarik

Previous computations of low-temperature Rosseland and Planck mean opacities from Alexander & Ferguson are updated and expanded. The new computations include a more complete equation of state (EOS) with more grain species and updated optical constants. Grains are now explicitly included in thermal equilibrium in the EOS calculation, which allows for a much wider range of grain compositions to be accurately included than was previously the case. The inclusion of high-temperature condensates such as Al2O3 and CaTiO3 significantly affects the total opacity over a narrow range of temperatures before the appearance of the first silicate grains. The new opacity tables are tabulated for temperatures ranging from 30,000 to 500 K with gas densities from 10-4 to 10-19 g cm-3. Comparisons with previous Rosseland mean opacity calculations are discussed. At high temperatures, the agreement with OPAL and Opacity Project is quite good. Comparisons at lower temperatures are more divergent as a result of differences in molecular and grain physics included in different calculations. The computation of Planck mean opacities performed with the opacity sampling method is shown to require a very large number of opacity sampling wavelength points; previously published results obtained with fewer wavelength points are shown to be significantly in error. Methods for requesting or obtaining the new tables are provided.

Opacity

10.1086/428642

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Citations (1,099)

Model atmospheres for M-dwarfs.

Mammalia (1990)

F. Allard

Source

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Citations (10)

Biomarkers of extrasolar planets and their observability

Cambridge University Press eBooks (2007)

Franck Selsis J. Paillet F. Allard

The first space-borne instruments able to detect and characterize extrasolar terrestrial planets, Darwin (ESA) and TPF (Terrestrial Planet Finder, NASA), should be launched at the end of the next decade. Beyond the challenge of planet detection itself, the ability to measure mid-infrared (Darwin, TPF-I) and visible (TPF-C) spectra at low resolution will allow us to characterize the exoplanets discovered. The spectral analysis of these planets will extend the field of planetary science beyond the Solar System to the nearby Universe. It will give access to certain planetary properties (albedo, brightness, temperature, radius) and reveal the presence of atmospheric compounds, which, together with the radiative budget of the planet, will provide the keys to understanding how the climate system works on these worlds. If terrestrial planets are sufficiently abundant, these missions will collect data for numerous planetary systems of different ages and orbiting different types of stars. Theories for the formation, evolution and habitability of the terrestrial planets will at last face the test of observation. The most fascinating perspective offered by these space observatories is the ability to detect spectral signatures indicating biological activity. In this chapter, we review and discuss the concept of extrasolar biosignatures or biomarkers. We focus mainly on the identification of oxygen-rich atmospheres through the detection of O2 and O3 features, addressing also the case of other possible biomarkers and indicators of habitability.

Habitability

Kepler-69c

Planetary habitability

10.1017/cbo9780511536533.010

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Citations (26)

REVISITINGSPITZERTRANSIT OBSERVATIONS WITH INDEPENDENT COMPONENT ANALYSIS: NEW RESULTS FOR THE GJ 436 SYSTEM

The Astrophysical Journal (2015)

Giuseppe Morello I. Waldmann G. Tinetti Ian D. Howarth G. Micela

We analyzed four Spitzer/IRAC observations at 3.6 and 4.5 {\mu}m of the primary transit of the exoplanet GJ436b, by using blind source separation techniques. These observations are important to investigate the atmospheric composition of the planet GJ436b. Previous analyses claimed strong inter-epoch variations of the transit parameters due to stellar variability, casting doubts on the possibility to extract conclusively an atmospheric signal; those analyses also reported discrepant results, hence the necessity of this reanalysis. The method we used has been proposed in Morello et al. (2014) to analyze 3.6 {\mu}m transit light-curves of the hot Jupiter HD189733b; it performes an Independent Component Analysis (ICA) on a set of pixel-light-curves, i.e. time series read by individual pixels, from the same photometric observation. Our method only assumes the independence of instrumental and astrophysical signals, and therefore guarantees a higher degree of objectivity compared to parametric detrending techniques published in the literature. The datasets we analyzed in this paper represent a more challenging test compared to the previous ones. Contrary to previous results reported in the literature, our results (1) do not support any detectable inter-epoch variations of orbital and stellar parameters, (2) are photometrically stable at the level 10e-4 in the IR, and (3) the transit depth measurements at the two wavelengths are consistent within 1{\sigma}. We also (4) detect a possible transit duration variation (TDV) of 80 s (2 {\sigma} significance level), that has not been pointed out in the literature, and (5) confirm no transit timing variations (TTVs) >30 s.

10.1088/0004-637x/802/2/117

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Citations (53)

Spectral Energy Distributions for Disk and Halo M Dwarfs

The Astrophysical Journal (2000)

S. K. Leggett F. Allard C. C. Dahn P. H. Hauschildt Tom Kerr

We have obtained infrared (1 to 2.5 micron) spectroscopy for 42 halo and disk dwarfs with spectral type M1 to M6.5. These data are compared to synthetic spectra generated by the latest model atmospheres of Allard & Hauschildt. Photospheric parameters metallicity, effective temperature and radius are determined for the sample. We find good agreement between observation and theory except for known problems due to incomplete molecular data for metal hydrides and water. The metal-poor M subdwarfs are well matched by the models as oxide opacity sources are less important in this case. The derived effective temperatures for the sample range from 3600K to 2600K; at these temperatures grain formation and extinction are not significant in the photosphere. The derived metallicities range from solar to one-tenth solar. The radii and effective temperatures derived agree well with recent models of low mass stars.

Photosphere

Opacity

Solar radius

Effective temperature

10.1086/308887

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Citations (185)

The Evolution of Irradiated Planets: Application to Transits

The Astrophysical Journal (2004)

Gilles Chabrier Travis Barman I. Baraffe F. Allard P. H. Hauschildt

Extending the theory that we derived recently for HD 209458b to different cases of strongly irradiated gaseous exoplanets, we have calculated the consistent evolution of a new transiting planet, OGLE-TR-56b, for its recently revised mass determination. The theory is shown to successfully reproduce the observed radius for the proper age of the system. We also examine the dissipation of kinetic energy at the planet's internal adiabat due to atmospheric winds and place constraints on the efficiency of this process. We show that a fraction ~0.1%-0.5% of the incident flux transformed into thermal energy deposited at the adiabatic level can accommodate the observed radii of both OGLE-TR-56b and HD 209458b. The present theory yields quantitative predictions on the evolution of the emergent spectrum and fundamental properties of hot jupiters. The predictions for radius, luminosity, temperature as a function of the planet's mass, and orbital distance can be used as benchmarks for future detections of transit planets.

Hot Jupiter

10.1086/383028

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Citations (56)

Model atmospheres for very cool hydrogen-rich white dwarfs

White Dwarfs (2008)

F. Allard R. Wehrsě

White (mutation)

10.1007/3-540-51031-1_322

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Citations (0)

Model Atmospheres for the ``Most Abnormal'' DZ White Dwarf