Testing Model Atmospheres for Young Very Low Mass Stars and Brown Dwarfs in the Infrared: Evidence for Significantly Underestimated Dust Opacities
arXiv:1412.7191 · doi:10.1088/0004-637X/805/1/57
Abstract
We test state-of-the-art model atmospheres for young very low-mass stars and brown dwarfs in the infrared, by comparing the predicted synthetic photometry over 1.2-24 μm to the observed photometry of M-type spectral templates in star-forming regions. We find that (1) in both early and late young M types, the model atmospheres imply effective temperatures (Teff) several hundred Kelvin lower than predicted by the standard Pre-Main Sequence spectral type-Teff conversion scale (based on theoretical evolutionary models). It is only in the mid-M types that the two temperature estimates agree. (2) The Teff discrepancy in the early M types (corresponding to stellar masses above 0.4 Msol at ages of a few Myr) probably arises from remaining uncertainties in the treatment of atmospheric convection within the atmospheric models, whereas in the late M types it is likely due to an underestimation of dust opacity. (3) The empirical and model-atmosphere J-band bolometric corrections are both roughly flat, and similar to each other, over the M-type Teff range. Thus the model atmospheres yield reasonably accurate bolometric luminosities (Lbol), but lead to underestimations of mass and age relative to evolutionary expectations (especially in the late M types) due to lower Teff. We demonstrate this for a large sample of young Cha I and Taurus sources. (4) The trends in the atmospheric model J-K colors, and their deviations from the data, are similar at Pre-Main Sequence and Main Sequence ages, suggesting that the model dust opacity errors we postulate here for young ages also apply at field ages.
arXiv comment45 pages, 12 figures, 3 tables. Accepted in ApJ
References in corpus (40)
- The chemical composition of the Sun
- The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
- The Limiting Effects of Dust in Brown Dwarf Model Atmospheres
- Models of Stars, Brown Dwarfs and Exoplanets
- The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 microns Using GLIMPSE Data
- Spectral Irradiance Calibration in the Infrared. XIV: the Absolute Calibration of 2MASS
- A high accuracy computed water line list
- Evolutionary models for low-mass stars and brown dwarfs: uncertainties and limits at very young ages
- The Occurrence Rate of Small Planets around Small Stars
- Astrometry and Photometry for Cool Dwarfs and Brown Dwarfs
- A Census of the Young Cluster IC 348
- Theory of Low-Mass Stars and Substellar Objects
- Model Atmospheres for M (Sub)Dwarfs: I. The base model grid
- The Disk Population of the Taurus Star-Forming Region
- Evolution of low-mass star and brown dwarf eclipsing binaries
- Infrared Extinction Toward Nearby Star-Forming Regions
- Young Low-Mass Stars and Brown Dwarfs in IC 348
- Mapping the Shores of the Brown Dwarf Desert II: Multiple Star Formation in Taurus-Auriga
- The Stellar Population of the Chamaeleon I Star-Forming Region
- Infrared Spectra and Spectral Energy Distributions of Late-M- and L-Dwarfs
- A Census of the Chamaeleon I Star-Forming Region
- The Disk Population of the Chamaeleon I Star-Forming Region
- The effect of magnetic activity on low-mass stars in eclipsing binaries
- Gravity Indicators in the Near-Infrared Spectra of Brown Dwarfs
- The effect of activity on stellar temperatures and radii
- Atmospheres from very low-mass stars to extrasolar planets
- The First Discovery of a Wide Binary Brown Dwarf
- A Surprising Reversal of Temperatures in the Brown-Dwarf Eclipsing Binary 2MASS J05352184-0546085
- A Multiplicity Census of Young Stars in Chamaeleon I
- Measuring Fundamental Parameters of Substellar Objects. I: Surface Gravities
- Measuring Fundamental Parameters of Substellar Objects. II: Masses and Radii
- Precision modeling of M dwarf stars: the magnetic components of CM Draconis
- Photometry using the Infrared Array Camera on the Spitzer Space Telescope
- Surprising dissimilarities in a newly formed pair of 'identical twin' stars
- Atmospheric Analysis of the M/L- and M/T-Dwarf Binary Systems LHS 102 and Gliese 229
- A short-period super-Earth orbiting the M2.5 dwarf GJ3634. Detection with Harps velocimetry and transit search with Spitzer photometry
- Circumstellar Environment and Effective Temperature of the Young Substellar Eclipsing Binary 2MASS J05352184-0546085
- High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity Uncertainties
- Spectral analysis of high resolution near-infrared spectra of ultra cool dwarfs
- High-Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. II. Secondary Spectrum: No Evidence that Spots Cause the Temperature Reversal