DISCOVERY OF A WIDE BINARY BROWN DWARF BORN IN ISOLATION

Journal Article · Sun Feb 01 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/691/2/1265· OSTI ID:21448961

Luhman, K L; Allen, P R ^[1]; Mamajek, E E ^[2]; Muench, A A

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1. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
2. Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

During a survey for stars with disks in the Taurus star-forming region using the Spitzer Space Telescope, we have discovered a pair of young brown dwarfs, FU Tau A and B, in the Barnard 215 dark cloud. They have a projected angular separation of 5.''7, corresponding to 800 AU at the distance of Taurus. To assess the nature of these two objects, we have obtained spectra of them and constructed spectral energy distributions. Both sources are young ({approx}1 Myr) according to their H{alpha} emission, gravity-sensitive spectral features, and mid-infrared excess emission. The proper motion of FU Tau A provides additional evidence of its membership in Taurus. We measure spectral types of M7.25 and M9.25 for FU Tau A and B, respectively, which correspond to masses of {approx}0.05 and {approx}0.015 M{sub sun} according to the evolutionary models of Chabrier and Baraffe. FU Tau A is significantly overluminous relative to an isochrone passing through FU Tau B and relative to other members of Taurus near its spectral type, which may indicate that it is an unresolved binary. FU Tau A and B are likely to be components of a binary system based on the low probability ({approx}3 x 10{sup -4}) that Taurus would produce two unrelated brown dwarfs with a projected separation of a {<=} 6''. Barnard 215 contains only one other young star and is in a remote area of Taurus, making FU Tau A and B the first spectroscopically confirmed brown dwarfs discovered forming in isolation rather than in a stellar cluster or aggregate. Because they were born in isolation and comprise a weakly bound binary, dynamical interactions with stars could not have played a role in their formation, and thus are not essential for the birth of brown dwarfs.

• OSTI ID: 21448961
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 691; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DWARF STARS
EMISSION
ENERGY SPECTRA
EVOLUTION
GRAVITATION
MASS
MOTION
PROPER MOTION
PROTOPLANETS
SPECTRA
STAR EVOLUTION
STARS
TELESCOPES