Volume 436, Number 2, June III 2005
|Page(s)||L39 - L42|
|Published online||30 May 2005|
Letter to the Editor
The cool atmospheres of the binary brown dwarf ε Indi B
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: firstname.lastname@example.org
2 DSM/DAPNIA/Service d'Astrophysique, CEA/Saclay, 91191 Gif-sur-Yvette, France
3 European Southern Observatory, 85748 Garching b. München, Germany
Accepted: 30 April 2005
We have imaged ε Indi B, the closest brown dwarf binary known, with VISIR at the VLT in three narrow-band mid-infrared bandpasses located around 8.6 μm, 10.5 μm and 11.3 μm. We are able to spatially resolve both components, and determine accurate mid-infrared photometry for both components independently. In particular, our VISIR observations probe the NH3 feature in the atmospheres of the cooler and warmer brown dwarfs. For the first time, we can disentangle the contributions of the two components, and find that ε IndiBb is in good agreement with recent “cloud-free” atmosphere models having an effective temperature of K. With an assumed age of 1 Gyr for the ε Indi system, component Ba agrees more with K rather than with K, as suggested by SPITZER spectroscopic observations of the combined ε Indi B system (Roellig et al. 2004). Even higher effective temperatures appear inconsistent with our absolute photometry, as they would imply an unphysical small size of the brown dwarf ε IndiBa.
Key words: stars: low-mass, brown dwarfs / stars: binaries: general
© ESO, 2005
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