Uniform Forward-modeling Analysis of Ultracool Dwarfs. III. Late-M and L Dwarfs in Young Moving Groups, the Pleiades, and the Hyades

• DOI: 10.3847/1538-4357/ad0b12
• Publication Date: 2024-01-18T11:44:06Z
• Authors: Spencer A. Hurt; Michael C. Liu; Zhoujian Zhang; Mark Phillips; Katelyn N. Allers; Niall R. Deacon; Kimberly M. Aller; William M. J. Best
• Keywords: Pleiades

Abstract We present a uniform forward-modeling analysis of 90 late-M and L dwarfs in nearby young (∼10–200 Myr) moving groups, the Pleiades, Hyades using low-resolution ( R ≈ 150) near-infrared (0.9–2.4 μ m) spectra BT-Settl model atmospheres. derive objects’ effective temperatures, surface gravities, radii, masses by comparing our to models Bayesian framework with nested sampling calculate same parameters evolutionary models. Assuming evolutionary-based are more robust, spectroscopically inferred from exhibit two types systematic behavior for objects near M-L spectral type boundary. Several clustered around T eff 1800 K <?CDATA $\mathrm{log}g\approx 5.5$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> <mml:mo>≈</mml:mo> <mml:mn>5.5</mml:mn> </mml:math> dex, implying impossibly large (150–1400 M Jup ), while others ≳ 3000 $\mathrm{log}g\lesssim 3.0$?> <mml:mo>≲</mml:mo> <mml:mn>3.0</mml:mn> unphysically low unreasonably ages. find fitted tend overpredict peak J - H -band flux located boundary, suggesting dust content included atmospheres is insufficient match observations. By adding an interstellar medium–like reddening law spectra, we fits between observed greatly improved, largest coefficients occurring at transition. This work delivers examination constitutes benchmark late-M- L-type brown date.