Weighing Three Brown Dwarfs

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Science  08 Jun 2001:
Vol. 292, Issue 5523, pp. 1799
DOI: 10.1126/science.292.5523.1799b

Brown dwarfs are failed stars; born with a low mass, they quickly ran out of deuterium for fusion and became dim cool remnants of stellar material. Although many brown dwarfs, including a few brown dwarf binary systems, have been identified, the mass of these objects and how they evolved are poorly understood.

In order to address some of these questions, Kenworthy et al. took a closer look at the brown dwarf binary system Gliese 569B. Using near-infrared bispectrum speckle interferometry techniques, they obtained spectra of the two dwarfs over a period of 1.5 years, which corresponds to about half of the orbital period of the system. Combined with infrared spectra, these results suggested that one of the binary dwarfs, Gliese 569Ba, may itself be composed of a tight binary system. This pair would orbit Gliese 569Bb at a separation of about 1 astronomical unit. In this model, orbital simulations indicate that each brown dwarf would weigh about 50 Jupiter masses and have similar luminosity and that this system would be young (only about 300 million years old). A three-brown-dwarf system would be consistent with current evolutionary models of how brown dwarf properties (mainly their mass and luminosity) change with time. — LR

Astrophys. J., in press.

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