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Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius

Kraus, Adam L. and Ireland, Michael J. and Martinache, Frantz and Lloyd, James P. (2008) Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius. Astrophysical Journal, 679 (1). pp. 762-782. ISSN 0004-637X. doi:10.1086/587435.

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We present the results of a survey for stellar and substellar companions to 82 young stars in the nearby OB association Upper Scorpius. This survey used nonredundant aperture mask interferometry to achieve typical contrast limits of ΔK ~5-6 at the diffraction limit, revealing 12 new binary companions that lay below the detection limits of traditional high-resolution imaging; we also summarize a complementary snapshot imaging survey that discovered seven directly resolved companions. The overall frequency of binary companions (~35 +5 -4% at separations of 6-435 AU) appears to be equivalent to field stars of similar mass, but companions could be more common among lower mass stars than for the field. The companion mass function has statistically significant differences compared to several suggested mass functions for the field, and we suggest an alternate lognormal parameterization of the mass function. Our survey limits encompass the entire brown dwarf mass range, but we only detected a single companion that might be a brown dwarf; this deficit resembles the so-called brown dwarf desert that has been observed by radial velocity planet searches. Finally, our survey’s deep detection limits extend into the top of the planetary mass function, reaching 8-12 MJup for half of our sample. We have not identified any planetary companions at high confidence (≳99.5%), but we have identified four candidate companions at lower confidence (≳97.5%) that merit additional follow-up to confirm or disprove their existence.

Item Type:Article
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URLURL TypeDescription
Kraus, Adam L.0000-0001-9811-568X
Ireland, Michael J.0000-0002-6194-043X
Martinache, Frantz0000-0003-1180-4138
Additional Information:©2008. The American Astronomical Society. Received 2007 November 26; accepted 2008 January 14. Print publication: Issue 1 (2008 May 20). The authors thank Lynne Hillenbrand for helpful feedback on the manuscript and Brian Cameron for sharing his NIRC2 astrometric calibration results prior to publication. We also thank the referee, Ralph Neuhäuser, for providing a helpful critique. We 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. A.L.K. is supported by a NASA/Origins grant to Lynne Hillenbrand. M.I. would like to acknowledge Michelson Fellowship support from the Michelson Science Center and the NASA Navigator Program. This work is also partially supported by the National Science Foundation under grants 0506588 and 0705085. This work makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC/Caltech, funded by NASA and the NSF. Our research has also made use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Michelson Science CenterUNSPECIFIED
U.S. Naval ObservatoryUNSPECIFIED
Subject Keywords:binaries: general; stars: low-mass, brown dwarfs; stars: pre–main-sequence
Issue or Number:1
Record Number:CaltechAUTHORS:KRAapj08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13246
Deposited On:05 Feb 2009 20:06
Last Modified:08 Nov 2021 22:36

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