2024ApJ...961..121H -
Astrophys. J., 961, 121 (2024/January-3)
Uniform Forward-modeling Analysis of Ultracool Dwarfs. III. Late-M and L Dwarfs in Young Moving Groups, the Pleiades, and the Hyades.
HURT S.A., LIU M.C., ZHANG Z., PHILLIPS M., ALLERS K.N., DEACON N.R., ALLER K.M. and BEST W.M.J.
Abstract (from CDS):
We present a uniform forward-modeling analysis of 90 late-M and L dwarfs in nearby young (∼10-200 Myr) moving groups, the Pleiades, and the Hyades using low-resolution (R ≈ 150) near-infrared (0.9-2.4 μm) spectra and the BT-Settl model atmospheres. We derive the objects' effective temperatures, surface gravities, radii, and masses by comparing our spectra to the models using a Bayesian framework with nested sampling and calculate the same parameters using evolutionary models. Assuming the evolutionary-based parameters are more robust, our spectroscopically inferred parameters from BT-Settl exhibit two types of systematic behavior for objects near the M-L spectral type boundary. Several objects are clustered around Teff ≈ 1800 K and $\mathrm{log}g\approx 5.5$ dex, implying impossibly large masses (150-1400 MJup), while others are clustered around Teff ≳ 3000 K and $\mathrm{log}g\lesssim 3.0$ dex, implying unphysically low masses and unreasonably young ages. We find the fitted BT-Settl model spectra tend to overpredict the peak J- and H-band flux for objects located near the M-L boundary, suggesting the dust content included in the model atmospheres is insufficient to match the observations. By adding an interstellar medium-like reddening law to the BT-Settl model spectra, we find the fits between models and observed spectra are greatly improved, with the largest reddening coefficients occurring at the M-L transition. This work delivers a systematic examination of the BT-Settl model atmospheres and constitutes the largest spectral analysis of benchmark late-M- and L-type brown dwarfs to date.
Abstract Copyright:
© 2024. The Author(s). Published by the American Astronomical Society.
Journal keyword(s):
Brown dwarfs - L dwarfs - M dwarf stars - Exoplanet atmospheres - Stellar atmospheres
Status at CDS
:
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Simbad objects:
100
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