Epsilon Indi Ba, Bb: a detailed study of the nearest known brown dwarfs (2009)
King, Robert R., McCaughrean, Mark J., Homeier, Derek, Allard, France, Scholz, Ralf-Dieter, Lodieu, Nicolas
The discovery of epsilon Indi Ba, Bb, a binary brown dwarf system very close to the Sun, makes possible a concerted campaign to characterise the physical parameters of two T dwarfs. Recent...
Epsilon Indi Ba, Bb: a spectroscopic study of the nearest known brown dwarfs (2008)
King, Robert R., McCaughrean, Mark J., Homeier, Derek, Allard, France, Scholz, Ralf-Dieter, Lodieu, Nicolas
The discovery of Epsilon Indi Ba and Bb, a nearby binary brown dwarf system with a main-sequence companion, allows a concerted campaign to characterise the physical parameters of two T dwarfs...
Fundamental Properties of Low-Mass Stars and Brown Dwarfs (2008)
Liu, Michael C., Stassun, Keivan G., Allard, France, Blake, Cullen H., Bonnefoy, M., Cody, Ann Marie, ...
Precise measurements of the fundamental properties of low-mass stars and brown dwarfs are key to understanding the physics underlying their formation and evolution. While there has been great...
Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results (2008)
Delorme, Philippe, Willott, Chris J., Forveille, Thierry, Delfosse, Xavier, Reylé, Céline, Bertin, Emmanuel, ...
We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to...
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition? (2008)
Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, ...
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii...
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition? (2008)
Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, ...
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii...
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition? (2008)
Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, ...
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii...
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition? (2008)
Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, ...
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii...
CFBDS J005910.90-011401.3: reaching the T-Y Brown Dwarf transition? (2008)
Delorme, Philippe, Delfosse, Xavier, Albert, Loic, Artigau, Etienne., Forveille, Thierry, Reylé, Céline, ...
We report the discovery of CFBDS J005910.90-011401.3 (hereafter CFBDS0059), the coolest brown dwarf identified to date. We found CFBDS0059 using i' and z' images from the Canada-France-Hawaii...
Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results (2008)
Delorme, Philippe, Willott, Chris, Forveille, Thierry, Delfosse, Xavier, Reylé, Céline, Bertin, Emmanuel, ...
We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to...
Finding ultracool brown dwarfs with MegaCam on CFHT: method and first results (2008)
Delorme, Philippe, Willott, Chris, Forveille, Thierry, Delfosse, Xavier, Reylé, Céline, Bertin, Emmanuel, ...
We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to...
K-H_2 Quasi-molecular absorption detected in the T-dwarf epsilon Indi Ba (2007)
Allard, France, Allard, Nicole F., Homeier, Derek, Kielkopf, John, McCaughrean, Mark J., Spiegelman, Fernand
T-type dwarfs present a broad and shallow absorption feature centred around 6950 A in the blue wing of the K doublet at 0.77 micron which resembles in depth and shape the satellite absorption...
Alkali Line Profiles in Ultracool White Dwarfs (2007)
Homeier, Derek, Allard, Nicole F., Johnas, Christine M. S., Hauschildt, Peter H., Allard, France
We present PHOENIX atmosphere models for metal-rich cool white dwarfs using improved line shapes for the Na I and K I resonance doublets. Profiles for collisional broadening due to H2 and He based on...
Alkali Line Profiles in Degenerate Dwarfs (2007)
Homeier, Derek, Allard, Nicole F., Allard, France
Ultracool stellar atmospheres show absorption by alkali resonance lines severely broadened by collisions with neutral perturbers. In the coolest and densest atmospheres, such as those of T dwarfs, Na...
Phase-Dependent Properties of Extrasolar Planet Atmospheres (2005)
Barman, Travis S., Hauschildt, Peter H., Allard, France
Recently the Spitzer Space Telescope observed the transiting extrasolar planets, TrES-1 and HD209458b. These observations have provided the first estimates of the day side thermal flux from two...
Low Temperature Opacities (2005)
Ferguson, Jason W., Alexander, David R., Allard, France, Barman, Travis, Bodnarik, Julia G., Hauschildt, Peter H., ...
Previous computations of low temperature Rosseland and Planck mean opacities from Alexander & Ferguson (1994) are updated and expanded. The new computations include a more complete equation of state...
Modelling Alkali Line Absorption and Molecular Bands in Cool DAZs (2005)
Homeier, Derek, Allard, Nicole F., Allard, France, Hauschildt, Peter H., Schweitzer, Andreas, Stancil, Phillip C., ...
Two peculiar stars showing an apparent extremely broadened and strong NaI D absorption have been discovered in surveys for cool white dwarfs by Oppenheimer et al. (2001) and Harris et al. (SDSS,...
Model Atmospheres for Irradiated Stars in pre-Cataclysmic Variables (2004)
Barman, Travis S., Hauschildt, Peter H., Allard, France
Model atmospheres have been computed for M dwarfs that are strongly irradiated by nearby hot companions. A variety of primary and secondary spectral types are explored in addition to models specific...
Spectral Properties of Brown Dwarfs and Hot Jupiters (2004)
Homeier, Derek, Allard, France, Hauschildt, Peter H., Barman, Travis S., Schweitzer, Andreas, Baron, Edward A.
Brown dwarfs bridge the gap between the stellar and planetary mass regimes. Evolving from conditions very similar to the lowest-mass stars, the atmospheres of older brown dwarfs closely resemble...
Measuring Fundamental Parameters of Substellar Objects. I: Surface Gravities (2004)
Mohanty, Subhanjoy, Basri, Gibor, Jayawardhana, Ray, Allard, France, Hauschildt, Peter, Ardila, David
(abridged) We present an analysis of high resolution optical spectra for a sample of very young, mid- to late M, low-mass stellar and substellar objects in Upper Sco and Taurus. Effective...
Multiplicity of Nearby Free-floating Ultra-cool Dwarfs: a HST-WFPC2 search for companions (2003)
Bouy, Herve, Brandner, Wolfgang, Martin, Eduardo L., Delfosse, Xavier, Allard, France, Basri, Gibor
We present HST/WFPC2 observations of a sample of 134 ultra-cool objects (spectral types later than M7) coming from the DENIS, 2MASS and SDSS surveys, with distances estimated to range from 7 pc to...
Model Atmospheres and Spectra: The Role of Dust (2003)
Allard, France, Guillot, Tristan, Ludwig, Hans-Günter, Hauschildt, Peter H., Schweitzer, Andreas, Alexander, David R., ...
Brown dwarf atmospheres form molecules, then high temperaturecondensates (corundum, titanates, silicates, and iron compounds), andthen low temperature condensates (ices) as they cool down over...
Convection and Dust in Cool Stellar Atmospheres (2003)
Ludwig, Hans-Günter, Freytag, Bernd, Höfner, Susanne, Allard, France, Hauschildt, Peter H.
We report on recent progress in hydrodynamical modelling of the surfacelayers of late M- and L-type main- as well as pre-main-sequence objects.Despite the complex chemistry encountered in the cool...
Bouy, Hervé, Brandner, Wolfgang, Martín, Eduardo L., Delfosse, Xavier, Allard, France, Basri, Gibor
We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of a sample of 134 ultracool objects (spectral types later than M7) coming from the Deep Near Infrared...
Detection of planets in disks (2003)
Steinacker, Jürgen, Henning, Th., Allard, France, Hauschildt, Peter, Dreizler, Stefan, Guenther, Eike, ...
Methane and the Spectra of T Dwarfs (2002)
Homeier, Derek, Hauschildt, Peter H., Allard, France
We have updated our PHOENIX model atmospheres and theoretical spectra for ultracool dwarfs with new opacity data for methane based on line strength predictions with the STDS software. By extending...
Non-LTE Effects of Na I in the Atmosphere of HD209458b (2002)
Barman, Travis S., Hauschildt, Peter H., Schweitzer, Andreas, Stancil, Phillip C., Baron, E., Allard, France
The recent announcement that sodium absorption has been observed in the atmosphere of HD209458b, the only EGP observed to transit its parent star, is the first direct detection of an EGP atmosphere....
Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres (2002)
Mohanty, Subhanjoy, Basri, Gibor, Shu, Frank, Allard, France, Chabrier, Gilles
Recent observations show that chromospheric activity in late-M and L dwarfs is much lower than in the earlier M types, in spite of comparatively rapid rotation. We investigate the possibility that...
Effective Temperatures of late L dwarfs and the onset of Methane signatures (2001)
Schweitzer, Andreas, Gizis, John E., Hauschildt, Peter H., Allard, France, Howard, Eric M., Kirkpatrick, J. Davy
We present a spectral analysis of a sample of late L dwarfs. We use our latest model atmospheres and synthetic spectra and optical and K band spectra to determine effective temperatures. We derive...
Infrared Spectroscopy of Substellar Objects in Orion (2001)
Lucas, P. W., Roche, P. F., Allard, France, Hauschildt, Peter H.
We present broad band spectra of a sample of 21 low luminosity sources in the Trapezium Cluster, with masses in the range 0.008 - 0.10 Msun (assuming an age of 1 Myr). These were selected for low...
The Limiting Effects of Dust in Brown Dwarf Model Atmospheres (2001)
Allard, France, Hauschildt, Peter H., Alexander, David R., Tamanai, Akemi, Schweitzer, Andreas
We present opacity sampling model atmospheres, synthetic spectra and colors for brown dwarfs and very low mass stars in two limiting case of dust grain formation: 1) inefficient gravitational...
Barman, Travis S., Hauschildt, Peter H., Allard, France
We have modeled irradiated planets located near a dM5 and a G2 primary star. The impinging radiation field was explicitly included in the solution of the radiative transfer equation and in the...
Analysis of Keck HIRES spectra of early L-type dwarfs (2001)
Schweitzer, Andreas, Gizis, John E., Hauschildt, Peter H., Allard, France, Reid, I. Neill
We present analyses of high resolution and medium resolution spectra of early L dwarfs. We used our latest set of model atmospheres to reproduce and analyze the observed features. We can model the...
Allard, France, Hauschildt, Peter H., Schweitzer, Andreas
We present a grid of spherically symmetric model atmospheres for young pre-MS stars. This grid spans the parameter range $2000\K \leq \Teff \leq 6800\K$ and $2.0 \leq \logg \leq 3.5$ for...
TiO and H$_2$O absorption lines in cool stellar atmospheres (2000)
Allard, France, Hauschildt, Peter H., Schwenke, David
We compare the structures of model atmospheres and synthetic spectra calculated using different line lists for TiO and water vapor. We discuss the effects of different line list combinations on the...
Basri, Gibor, Mohanty, Subhanjoy, Allard, France, Hauschildt, Peter H., Delfosse, Xavier, Martin, Eduardo L., ...
We present Keck HIRES spectra of 6 late-M dwarfs and 11 L dwarfs. Our goal is to assign effective temperatures to the objects using detailed atmospheric models and fine analysis of the alkali...
Hauschildt, Peter H., Allard, France, Ferguson, Jason, Baron, E., Alexander, David R.
We present the extension of our NextGen model atmosphere grid to the regime of giant stars. The input physics of the models presented here is nearly identical to the NextGen dwarf atmosphere models,...
Peter H. Hauschildt, France Allard, Jason Ferguson, E. Baron, David R. Alexander
We present the extension of our NextGen model atmosphere grid to the regime of giant stars. The input physics of the models presented here is nearly identical to the NextGen dwarf atmosphere models,...
The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$ (1998)
Hauschildt, Peter H., Allard, France, Baron, E.
We present our NextGen Model Atmosphere grid for low mass stars for effective temperatures larger than $3000\K$. These LTE models are calculated with the same basic model assumptions and input...
Baraffe, Isabelle, Chabrier, Gilles, Allard, France, Hauschildt, Peter
We present evolutionary models for low mass stars from 0.075 to 1 $\msol$ for solar-type metallicities [M/H]= 0 and -0.5. The calculations include the most recent interior physics and the latest...
Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program (1998)
Peter H. Hauschildt, E. Baron, France Allard
We describe the parallel implementation of our generalized stellar atmosphere and NLTE radiative transfer computer program PHOENIX. We discuss the parallel algorithms we have developed for radiative...
Betaine Improves Freezing Tolerance in Wheat (1998)
Allard, France, Houde, Mario, Kröl, Marianna, Ivanov, Alexander, Huner, Norman P.A., Sarhan, Fathey
The accumulation of the osmolyte betaine was found to be correlated with the development of freezing tolerance (FT) of two wheat cultivars where it increases by about three fold during the cold...
Atmosphere Models for Very Low Mass Stars, Brown Dwarfs and Exoplanets (1997)
Baraffe, Isabelle, Allard, France
Over the past decade considerable effort, both observational and theoretical, has been directed towards a more accurate determination of the stellar lower main sequence and of the sub-stellar domain...
NLTE effects of Ti~I in M dwarfs and giants (1997)
Hauschildt, Peter H., Allard, France, Alexander, David R., Baron, E.
We present detailed NLTE Ti~I calculations in model atmospheres of cool dwarf and giant stars. A fully self-consistent NLTE treatment for a Ti~I model atom with 395 levels and 5279 primary...
Brown Dwarfs from the Stellar Perspective (1997)
Allard, France, Hauschildt, Peter H.
In this paper, we review the current theory of very low mass stars model atmospheres including the coolest known M~dwarfs, M~subdwarfs, and brown dwarfs, i.e. T$_{eff} \leq 5,000 $K and $-2.0 \le...
Baraffe, Isabelle, Chabrier, Gilles, Allard, France, Hauschildt, Peter
We have performed evolutionary calculations of very-low-mass stars from 0.08 to 0.8 $\msol$ for different metallicites from [M/H]= -2.0 to -1.0 and we have tabulated the mechanical, thermal and...
Non-LTE model atmosphere analysis of the early ultraviolet spectra of nova OS Andromedae 1986 (1996)
Schwarz, Greg, Hauschildt, Peter H., Starrfield, Sumner, Baron, Eddie, Allard, France, Shore, Steve, ...
We have analyzed the early optically thick ultraviolet spectra of Nova OS And 1986 using a grid of spherically symmetric, non-LTE, line-blanketed, expanding model atmospheres and synthetic spectra...
Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program (1996)
Hauschildt, Peter H., Baron, E., Allard, France
We describe the parallel implementation of our generalized stellar atmosphere and NLTE radiative transfer computer program PHOENIX. We discuss the parallel algorithms we have developed for radiative...
Analysis of Keck High Resolution Spectra of VB10 (1996)
Schweitzer, Andreas, Hauschildt, Peter H., Allard, France, Basri, G.
We use a preliminary version of our ``NextGen'' grid of cool star model atmospheres to compute synthetic line profiles which fit high resolution Keck spectra of the cool M~dwarf VB10 satisfactorily...
Synthetic Spectra and Mass Determination of the Brown Dwarf Gl229B (1996)
Allard, France, Hauschildt, Peter H., Baraffe, Isabelle, Chabrier, Gilles
We present preliminary non-grey model atmospheres and interiors for cool brown dwarfs. The resulting synthetic spectra are compared to available spectroscopic and photometric observations of the...
NLTE Model Atmospheres for M Dwarfs and Giants (1996)
Hauschildt, Peter H., Allard, France, Alexander, David R., Schweitzer, Andreas, Baron, E.
The atmospheres of M stars are dominated by a small number of very strong molecular compounds (H$_2$O, TiO, H$_2$, CO, VO). Most of the hydrogen is locked in molecular H$_2$, most of the carbon in...
The Effects of Fe II NLTE on Nova Atmospheres and Spectra (1996)
Hauschildt, Peter H., Baron, E., Starrfield, Sumner, Allard, France
The atmospheres of novae at early times in their outbursts are very extended, expanding shells with low densities. Models of these atmospheres show that NLTE effects are very important and must be...
Model Atmospheres for M (Sub)Dwarfs: I. The base model grid (1996)
Allard, France, Hauschildt, Peter H.
We have calculated a grid of more than 700 model atmospheres valid for a wide range of parameters encompassing the coolest known M~dwarfs, M~subdwarfs and brown dwarf candidates: $1500\le \teff \le...