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First Ultraviolet Spectrum of a Brown Dwarf: Evidence for H_2 Fluorescence and Accretion

John E. Gizis·Harry L. Shipman·James A. Harvin
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Abstract

We analyze an HST/STIS ultraviolet spectrum of the young brown dwarf 2MASSW J1207334-393254, a member of the ten million-year old TW Hya Association that has a planetary-mass companion. We detect and identify numerous emission lines. CIV and other ions are seen that arise in hot gas. We identify a series of lines with Lyman-pumped H_2 molecular lines, indicating that cool gas is also present. Overall, this substellar object shows many of the same characteristics as classical T Tauri stars. We interpret our results as direct evidence of accretion from a circumstellar gas disk, consistent with previous claims. The lack of SiIV emission from the accreting gas indicates that silicon has been depleted into grains.

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John E. Gizis, Harry L. Shipman, James A. Harvin. 2005-07-19. First Ultraviolet Spectrum of a Brown Dwarf: Evidence for H_2 Fluorescence and Accretion. https://doi.org/10.1086/462414

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