Evolutionary Models for Very Low-Mass Stars and Brown Dwarfs with Dusty Atmospheres

By G. Chabrier, Isabelle Baraffe, F. Allard, Peter Hauschildt. 2000

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We present evolutionary calculations for very low-mass stars and brown dwarfs based on synthetic spectra and nongray atmosphere models which include dust formation and opacity, i.e., objects with Teff ≲ 2800 K. The interior of the most massive brown dwarfs is shown to develop a conductive core after ~2 Gyr which slows down their cooling. Comparison is made in optical and infrared color-magnitude diagrams with recent late-M and L dwarf observations. The saturation in optical colors and the very red near-infrared colors of these objects are well explained by the onset of dust formation in the atmosphere. Comparison of the faintest presently observed L dwarfs with these dusty evolutionary models suggests that dynamical processes such as turbulent diffusion and gravitational settling are taking place near the photosphere. As the effective temperature decreases below Teff ≈ 1300-1400 K, the colors of these objects move to very blue near-infrared colors, a consequence of the ongoing methane absorption in the infrared. We suggest the possibility of a brown dwarf dearth in J, H, and K color-magnitude diagrams around this temperature.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/729169ce2f2ba268a34a5d9ead0177df4468e77d

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Citations in the corpus

BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, methodology): “Using the DUSTY evolution models (Chabrier et al. 2000), the presence of Li and the spectrophotometric absolute magnitude of this object, they determined that it should be younger than 500 Myr and less massive than 50 MJup.”
Low-Luminosity Companions to White Dwarfs (2005, methodology): “This corresponds to spectral types later than T8, Teff < 750 K, and M ∼ 0.020− 0.040 M⊙ for 1− 5 Gyr (Vrba et al. 2004; Leggett et al. 2002; Chabrier et al. 2000).”
THE PALOMAR/KECK ADAPTIVE OPTICS SURVEY OF YOUNG SOLAR ANALOGS: EVIDENCE FOR A UNIVERSAL COMPANION MASS FUNCTION (2008, methodology): “Indeed, the more recent DUSTY models from the Lyon group (Chabrier et al. 2000) do not extend above 3000 K, since dust is not expected to form in stellar photospheres at such high effective temperatures.”
THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES (2008, background): “For the most distant cloud (Serpens), a mainsequence luminosity of 0.05 L⊙ implies a mass of 0.08 M⊙, while 0.01 L⊙ correponds to 0.04 M⊙ (Chabrier et al. 2000).”
Flaring up All Over—Radio Activity in Rapidly Rotating Late M and L Dwarfs (2001, background): “(2) Assuming that the emission is coronal, we can useR∼ (2− 4)Rs ∼ (2− 4)RJ as the size of the corona in units of Jupiter radii (Linsky & Gary 1983; Dorman, Nelson, & Chau 1989; Burrows, Hubbard, & Lunine 1989; Chabrier et al. 2000; Leto et al. 2000).”
MASSES, RADII, AND CLOUD PROPERTIES OF THE HR 8799 PLANETS (2012, background): “The earliest models for these objects assumed that the condensates were uniformly distributed vertically throughout the atmosphere (e.g., Chabrier et al. 2000).”
THE GEMINI/NICI PLANET-FINDING CAMPAIGN: THE FREQUENCY OF PLANETS AROUND YOUNG MOVING GROUP STARS (2013, methodology): “We interpolated from both the DUSTY and COND models of Chabrier et al. (2000) and Baraffe et al. (2002, 2003) using the maximum detectable apparent magnitudes, distance, and age of each stars to estimate the minimum detectable mass curves.”
A YOUNG PROTOPLANET CANDIDATE EMBEDDED IN THE CIRCUMSTELLAR DISK OF HD 100546 (2013, background): “Photospheric emission: If the observed point source flux arose solely from the photosphere of a young object the COND and DUSTY models suggest masses between ∼15 – 20 MJupiter for an age of 5 – 10 Myr (Baraffe et al. 2003; Chabrier et al. 2000).”
Adaptive Optics for Astronomy (2012, background): “Intriguingly, while theoretical tracks (Chabrier et al. 2000) are a reasonable match to the data for low mass stars, applying the same atmospheric models to even lower masses (< 13MJ ) fails to predict the very red low luminosity objects now known as giant exoplanets (see Sec.”
PHOTOMETRIC REDSHIFT AND CLASSIFICATION FOR THE XMM–COSMOS SOURCES (2008, methodology): “We constructed a spectral library of low mass stars (Chabrier et al. 2000) and subdwarf O and B stars, white dwarfs and binary systems (Bixler et al. 1991).”
A probable giant planet imaged in the beta Pictoris disk. VLT/NaCo deep L'-band imaging (2008, methodology): “With anL′ magnitude of 11.2± 0.3, and assuming a distance of 19.3± 0.2 pc and an age of 12+8 −4 Myr (Zuckerman et al. 2001), the mass of the CC is estimated to 9+3 −2 MJup using COND models (Baraffe et al. 2003) and 8+4 −2 MJup using DUSTY models (Chabrier et al. 2000).”
Confirmation of the Electron Cyclotron Maser Instability as the Dominant Source of Radio Emission from Very Low Mass Stars and Brown Dwarfs (2008, methodology): “By correlating available data, such as lithium abundance and bolometric luminosity with the evolutionary models put forward by Baraffe et al (1998) and Chabrier et al. (2000), we attempt to constrain the age, mass and hence radius, for all three dwarfs.”
The Substellar Mass Function in σ Orionis (2001, methodology): “This location is suitably reproduced by the combination of the 5 Myr ““ dust-free and dusty ÏÏ Lyon models (Bara†e et al. 1998 ; Chabrier et al. 2000), as shown in Figure 1.”
Brown dwarfs in the Pleiades cluster: Clues to the substellar mass function , (2002, methodology): “For example, the brown dwarf candidates with I between 20.2 and 21.7 have a temperature of ∼2000 K (Chabrier et al. 2000).”
New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit (2015, methodology): “The impact of the TiO linelist has already been noticed with the generation of models following the NextGen ones, such as the Dusty models (Chabrier et al., 2000; Allard et al., 2001).”
LkCa 15: A YOUNG EXOPLANET CAUGHT AT FORMATION? (2011, methodology): “By contrast, models which assume a higher-entropy initial state as for collapse out of a gas cloud (the “hot start” models) (Chabrier et al. 2000) predict that young planets could be as bright as ∼ 10−3 L⊙.”
CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b (2011, background): “While the implied mass of ∼ 0.7 MJup is comfortably within the ranged needed for dynamical stability, it is difficult to form objects, either by core-accretion or by gravitational instability, with this mass, radius (∼ 0.75 RJup), and the planet’s observed luminosity.”
Detecting gravitational wave emission from the known accreting neutron stars (2008, background): “For intermediate orbital periods more options are possible, maximum donor mass being by the main sequence star - but evolved, less massive companions or even brown dwarfs may be possible (Tout et al. 1996; Chabrier & Baraffe 2000; Chabrier et al. 2000; Bildsten & Chakrabarty 2001)11.”