A USNO Search for Astrometric Companions to Brown Dwarfs

Details A USNO Search for Astrometric Companions to Brown Dwarfs A USNO Search for Astrometric Companions to Brown Dwarfs

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21934524b&link_type=abstract

American Astronomical Society, AAS Meeting #219, #345.24

Astronomy and Astrophysics

Astronomy

Scientific paper

Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m Strand Astrometric Reflector from 2000 September through 2006 April over periods from 3.0 to 5.4 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method.
The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures.
The brown dwarfs in this subsample have spectral types in the late L and mid- to late-T ranges, including one L subdwarf. None are known binaries. Preliminary parallaxes place them within 30 pc; half of these are probable members of the Solar Neighborhood because they lie within 25 pc, including two within 10 pc. These substellar objects are located north of -25° Dec. and lie between 0h and 9h in R.A.
The brown dwarfs evaluated are 2MASS J00303013-1450333, 2MASS J02431371-2453298, 2MASS J03284265+2302051, 2MASS J04151954-0935066, 2MASS J05160945-0445499, 2MASS J05325346+8246465, 2MASS J05591914-1404488, 2MASS J07271824+1710012, 2MASS J07554795+2212169, and 2MASS J08251968+2115521. Analyses of 39 more brown dwarfs are planned.

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