TY - JOUR
T1 - L-band spectroscopy of young brown dwarfs
AU - Beiler, Samuel A.
AU - Allers, Katelyn N.
AU - Cushing, Michael
AU - Faherty, Jacqueline
AU - Marley, Mark
AU - Skemer, Andrew
N1 - Funding Information:
Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation (NSF) on behalf of the Gemini partnership: the NSF (USA), the National Research Council (Canada), Comisión Nacional de Investigación Científica y Tecnológica (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). Katelyn Allers and Samuel Beiler are grateful for support from the Isaac J. Tressler fund for astronomy at Bucknell University, and the Doreen and Lyman Spitzer Graduate Fellowship in Astrophysics at the University of Toledo. This work benefitted from the Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, USA, a program funded by the Heising-Simons Foundation. We appreciated conversations with Brittney Miles which enhanced this work, and we would like to thank Denise Stephens for contributing the 2MASS 2244+20 spectrum, and Pascal Tremblin for allowing us access to unpublished models. This work has benefited from The UltracoolSheet at http://bit.ly/UltracoolSheet, maintained by Will Best, Trent Dupuy, Michael Liu, Rob Siverd, and Zhoujian Zhang, and developed from compilations by Dupuy & Liu (2012), Dupuy & Kraus (2013), Liu et al. (2016), and Best et al. (2018, 2020b).
Publisher Copyright:
© 2022 The Author(s)
PY - 2023/2/1
Y1 - 2023/2/1
N2 - We present a L-band (2.98–3.96 μm) spectroscopic study of eight young L dwarfs with spectral types ranging from L2 to L7. Our spectra (λ/∆λ ≈ 250–600) were collected using the Gemini near-infrared spectrograph. We first examine the young L-band spectral sequence, most notably analysing the evolution of the Q-branch of methane absorption feature at 3.3 μm. We find the Q-branch feature first appears between L3 and L6, as previously seen in older field dwarfs. Secondly, we analyse how well various atmospheric models reproduce the L band and published near-IR (0.7–2.5 μm) spectra of our objects by fitting five different grids of model spectra to the data. Best-fit parameters for the combined near-IR and L-band data are compared to best-fit parameters for just the near-IR data, isolating the impact that the addition of the L band has on the results. This addition notably causes a ∼100 K drop in the best-fit effective temperature. Also, when clouds and a vertical mixing rate (Kzz) are included in the models, thick clouds, and higher Kzz values are preferred. Five of our objects also have previously published effective temperatures and surface gravities derived using evolutionary models, age estimates, and bolometric luminosities. Comparing model spectra matching these parameters to our spectra, we find disequilibrium chemistry and clouds are needed to match these published effective temperatures. Three of these objects are members of AB Dor, allowing us to show the temperature dependence of the Q-branch of methane.
AB - We present a L-band (2.98–3.96 μm) spectroscopic study of eight young L dwarfs with spectral types ranging from L2 to L7. Our spectra (λ/∆λ ≈ 250–600) were collected using the Gemini near-infrared spectrograph. We first examine the young L-band spectral sequence, most notably analysing the evolution of the Q-branch of methane absorption feature at 3.3 μm. We find the Q-branch feature first appears between L3 and L6, as previously seen in older field dwarfs. Secondly, we analyse how well various atmospheric models reproduce the L band and published near-IR (0.7–2.5 μm) spectra of our objects by fitting five different grids of model spectra to the data. Best-fit parameters for the combined near-IR and L-band data are compared to best-fit parameters for just the near-IR data, isolating the impact that the addition of the L band has on the results. This addition notably causes a ∼100 K drop in the best-fit effective temperature. Also, when clouds and a vertical mixing rate (Kzz) are included in the models, thick clouds, and higher Kzz values are preferred. Five of our objects also have previously published effective temperatures and surface gravities derived using evolutionary models, age estimates, and bolometric luminosities. Comparing model spectra matching these parameters to our spectra, we find disequilibrium chemistry and clouds are needed to match these published effective temperatures. Three of these objects are members of AB Dor, allowing us to show the temperature dependence of the Q-branch of methane.
KW - brown dwarfs
KW - planets and satellites: atmospheres
KW - stars: atmosphere
KW - stars: low-mass
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U2 - 10.1093/mnras/stac3307
DO - 10.1093/mnras/stac3307
M3 - Article
AN - SCOPUS:85159568167
SN - 0035-8711
VL - 518
SP - 4870
EP - 4894
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -