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Clouds, Gravity, and Metallicity in Blue L Dwarfs: The Case of 2MASS J11263991–5003550

Burgasser, Adam J. and Looper, Dagny L. and Kirkpatrick, J. Davy and Cruz, Kelle L. and Swift, Brandon J. (2008) Clouds, Gravity, and Metallicity in Blue L Dwarfs: The Case of 2MASS J11263991–5003550. Astrophysical Journal, 674 (1). pp. 451-465. ISSN 0004-637X. doi:10.1086/524726.

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Optical and near-infrared spectroscopy of the newly discovered peculiar L dwarf 2MASS J11263991–5003550 are presented. Folkes et al. classified this source as a high proper motion L9±1 dwarf based on its strong H2O absorption at 1.4 μ m . We find that the optical spectrum of 2MASS J1126–5003 is in fact consistent with that of a normal L4.5 dwarf with notably enhanced FeH absorption at 9896 Å. However, its near-infrared spectrum is unusually blue, with strong H2O and weak CO bands similar in character to several recently identified "blue L dwarfs." Using 2MASS J1126–5003 as a case study, and guided by trends in the condensate cloud models of Burrows et al. and Marley et al., we find that the observed spectral peculiarities of these sources can be adequately explained by the presence of thin and/or large-grained condensate clouds as compared to normal field L dwarfs. Atypical surface gravities or metallicities alone cannot reproduce the observed peculiarities, although they may be partly responsible for the unusual condensate properties. We also rule out unresolved multiplicity as a cause for the spectral peculiarities of 2MASS J1126–5003. Our analysis is supported by examination of Spitzer mid-infrared spectral data from Cushing et al. which show that bluer L dwarfs tend to have weaker 10 μ m absorption, a feature tentatively associated with silicate oxide grains. With their unique spectral properties, blue L dwarfs like 2MASS J1126–5003 should prove useful in studying the formation and properties of condensates and condensate clouds in low-temperature atmospheres.

Item Type:Article
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URLURL TypeDescription
Burgasser, Adam J.0000-0002-6523-9536
Kirkpatrick, J. Davy0000-0003-4269-260X
Cruz, Kelle L.0000-0002-1821-0650
Additional Information:© 2008 The American Astronomical Society. Received 2007 August 3; accepted 2007 October 4. The authors thank Adam Burrows, Mark Marley, and Didier Saumon for providing spectral models for our analysis and comments on the original manuscript, and Michael Cushing for making available his Spitzer IRS data. We would also like to thank telescope operator Bill Golisch and instrument specialist John Rayner at IRTF, and telescope operator Hernán Nuñez at Magellan for their assistance during the observations. Additional appreciation goes to our anonymous referee for her/his prompt review. This publication makes use of data from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, and is funded by the National Aeronautics and Space Administration and the National Science Foundation. 2MASS data were obtained from the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has benefitted from the M, L, and T dwarf compendium housed at and maintained by Chris Gelino, Davy Kirkpatrick, and Adam Burgasser. K. L. C is supported by a NSF Astronomy and Astrophysics Postdoctoral Fellowship under AST 04-01418. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: IRTF(SpeX), Magellan:Clay(LDSS-3) This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NSFAST 04-01418
Subject Keywords:stars : atmospheres; stars : fundamental parameters; stars : individual (2MASS J11263991-5003550); stars : low-mass, brown dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20090408-095854933
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13892
Deposited By: Ruth Sustaita
Deposited On:17 Jul 2009 16:19
Last Modified:08 Nov 2021 22:41

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