| 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, and the Hyades using low-resolution ( R ≈ 150) near-infrared (0.9–2.4 μ m) 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 T eff ≈ 1800 K and <?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 masses (150–1400 M Jup ), while others are clustered around T eff ≳ 3000 K and <?CDATA $\mathrm{log}g\lesssim 3.0$?> <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>3.0</mml:mn> </mml:math> 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. |
| Authors |
Spencer A. Hurt   , Mengmeng Liu , Zhoujian Zhang , M. W. Phillips , Katelyn Allers , N. R. Deacon , Kimberly M. Aller , William M. J. Best
|
| Journal Info |
IOP Publishing | The Astrophysical Journal , vol: 961
, iss: 1
, pages: 121 - 121
|
| Publication Date |
1/1/2024 |
| ISSN |
0004-637X |
Type |
article |
| Open Access |
gold
|
| DOI |
https://doi.org/10.3847/1538-4357/ad0b12 |
| Keywords |
Young Stellar Objects (Score: 0.497789)
|
