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The NIRSPEC Brown Dwarf Spectroscopic Survey. II. High-Resolution J-Band Spectra of M, L, and T Dwarfs

McLean, Ian S. and Prato, L. and McGovern, Mark R. and Burgasser, Adam J. and Kirkpatrick, J. Davy and Rice, Emily L. and Kim, Sungsoo S. (2007) The NIRSPEC Brown Dwarf Spectroscopic Survey. II. High-Resolution J-Band Spectra of M, L, and T Dwarfs. Astrophysical Journal, 658 (2). pp. 1217-1235. ISSN 0004-637X. doi:10.1086/511740.

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We present a sequence of high-resolution (R ~ 20,000, or 15 km s^(-1)) infrared spectra of stars and brown dwarfs spanning spectral types M2.5 to T6. Observations of 16 objects were obtained using eight echelle orders to cover part of the J band from 1.165-1.323 μm with NIRSPEC on the Keck II telescope. By comparing opacity plots and line lists, over 200 weak features in the J band are identified with either FeH or H2O transitions. Absorption by FeH attains maximum strength in the mid-L dwarfs, while H_2O absorption becomes systematically stronger toward later spectral types. Narrow resolved features broaden markedly after the M to L transition. Our high-resolution spectra also reveal that the disappearance of neutral Al lines at the boundary between M and L dwarfs is remarkably abrupt, presumably because of the formation of grains. Neutral Fe lines can be traced to mid-L dwarfs before Fe is removed by condensation. The neutral potassium (K I) doublets that dominate the J band have pressure-broadened wings that continue to broaden from ~50 km s^(-1) (FWHM) at mid M to ~500 km s^(-1) at mid T. In contrast, however, the measured pseudo-equivalent widths of these same lines reach a maximum in the mid-L dwarfs. The young L2 dwarf, G196-3B, exhibits narrow potassium lines without extensive pressure-broadened wings, indicative of a lower gravity atmosphere. Kelu-1AB, another L2, has exceptionally broad infrared lines, including FeH and H_2O features, confirming its status as a rapid rotator. In contrast to other late-T objects, the peculiar T6 dwarf 2MASS 0937+29 displays a complete absence of potassium even at high resolution, which may be a metallicity effect or a result of a cooler, higher gravity atmosphere.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Burgasser, Adam J.0000-0002-6523-9536
Kirkpatrick, J. Davy0000-0003-4269-260X
Rice, Emily L.0000-0002-3252-5886
Additional Information:© 2007 The American Astronomical Society. Received 2006 July 28; accepted 2006 November 15. The authors wish to thank the staff of the Keck Observatory for their outstanding support. I. S. M. acknowledges the staff of the UCLA Infrared Laboratory and colleagues James Graham (University of California, Berkeley), James Larkin (UCLA), and Eric Becklin (UCLA) for their support throughout the development of the NIRSPEC instrument. We thank Adam Burrows, Katharina Lodders, Linda Brown, Didier Saumon, Richard Freedman, Travis Barman, and Mark Marley for helpful discussions and opacity data. Finally, we thank the anonymous referee for a careful and complete critique of this paper. Work by S. S. K. was supported by the Astrophysical Research Center for the Structure and Evolution of the Cosmos (ARCSEC) of the Korea Science and Engineering Foundation through the Science Research Center (SRC) program. A. J. B. acknowledges support by NASA through Hubble Fellowship grant HST-HF-01137.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., for NASA, under contract NAS5-26555. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA. This publication makes use of data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC, funded by NASA and the National Science Foundation.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Korea Science and Engineering FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF-01137.01
Subject Keywords:infrared : stars; stars : atmospheres; stars : low-mass, brown dwarfs
Issue or Number:2
Record Number:CaltechAUTHORS:20100218-134834712
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Official Citation:The NIRSPEC Brown Dwarf Spectroscopic Survey. II. High-Resolution J-Band Spectra of M, L, and T Dwarfs Ian S. McLean, L. Prato, Mark R. McGovern, Adam J. Burgasser, J. Davy Kirkpatrick, Emily L. Rice, and Sungsoo S. Kim 2007 ApJ 658 1217-1235 doi: 10.1086/511740
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17524
Deposited By: Tony Diaz
Deposited On:19 Feb 2010 17:44
Last Modified:08 Nov 2021 23:36

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