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Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839–0446358

Burgasser, Adam J. and Liu, Michael C. and Ireland, Michael J. and Cruz, Kelle L. and Dupuy, Trent J. (2008) Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839–0446358. Astrophysical Journal, 681 (1). pp. 579-593. ISSN 0004-637X. doi:10.1086/588379.

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Evidence is presented that 2MASS J03202839–0446358, a late-type dwarf with discrepant optical (M8:) and near-infrared (L1) spectral types, is an as-yet unresolved stellar/brown dwarf binary with late-type M dwarf and T dwarf components. This conclusion is based on low-resolution, near-infrared spectroscopy that reveals a subtle but distinctive absorption feature at 1.6 μ m . The feature, which is also present in the combined light spectrum of the M8.5 + T6 binary SCR 1845–6357, arises from the combination of FeH absorption from an M8.5 primary and pseudocontinuum flux from a T5 ± 1 secondary, as ascertained from binary spectral templates constructed from empirical data. The binary templates provide a far superior match to the overall near-infrared spectral energy distribution of 2MASS J0320–0446 than any single comparison spectra. Laser guide star adaptive optics (LGS AO) imaging observations, including the first application of LGS AO aperture mask interferometry, fail to resolve a faint companion, restricting the projected separation of the system to less than 8.3 AU at the time of observation. 2MASS J0320–0446 is the second very low mass binary to be identified from unresolved, low-resolution, near-infrared spectroscopy, a technique that complements traditional high-resolution imaging and spectroscopic methods.

Item Type:Article
Related URLs:
URLURL TypeDescription
Burgasser, Adam J.0000-0002-6523-9536
Liu, Michael C.0000-0003-2232-7664
Ireland, Michael J.0000-0002-6194-043X
Cruz, Kelle L.0000-0002-1821-0650
Dupuy, Trent J.0000-0001-9823-1445
Additional Information:© 2008. The American Astronomical Society. Received 2008 January 4; accepted 2008 March 3; published 2008 July 1. The authors acknowledge telescope operator Paul Sears and instrument specialist John Rayner at IRTF, and Al Conrad, Randy Campbell, Jason McIlroy, and Gary Punawai at Keck, for their assistance during the observations. We also thank Markus Kasper for providing the spectral data for SCR 1845–6357 and Sandy Leggett, Dagny Looper, and Kevin Luhman for providing a portion of the SpeX prism spectra used in the binary spectral template analysis. Our anonymous referee provided a helpful and very prompt critique of the original manuscript. M. C. L. and T. J. D. acknowledge support for this work from NSF grant AST 05-07833 and an Alfred P. Sloan Research Fellowship. This publication makes use of data from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, and 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; the VLM Binaries Archive maintained by Nick Siegler at; and the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at 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),Keck:I(NIRC2, LGS) Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NSFAST 05-07833
Alfred P. Sloan FoundationUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries : general; stars : fundamental parameters; stars : individual; stars : low-mass, brown dwarfs
Issue or Number:1
Record Number:CaltechAUTHORS:20090409-073715618
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13898
Deposited By: Ruth Sustaita
Deposited On:17 Jul 2009 17:18
Last Modified:08 Nov 2021 22:41

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