Volume 550, February 2013
|Number of page(s)||4|
|Published online||21 January 2013|
GTC OSIRIS z-band imaging of Y dwarfs
1 Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
e-mail: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org
2 Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
3 Consejo Superior de Investigaciones Científicas, CSIC, Spain
Received: 5 November 2012
Accepted: 28 December 2012
Aims. The aim of the project is to contribute to the characterisation of the spectral energy distribution of the coolest brown dwarfs discovered to date, the Y dwarfs.
Methods. We obtained z-band far-red imaging for six Y dwarfs and a T9 + Y0 binary with the OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) instrument on the 10.4-m Gran Telescopio de Canarias (GTC).
Results. We detect five of the seven known Y dwarfs in the z-band, infer their optical-to-infrared colours, and measure their proper motions. We find a higher dispersion in the z − J and z − H colours of Y0 dwarfs than in T dwarfs. This dispersion is found to be correlated with H − w2. The high dispersion in the optical-to-infrared colours of Y dwarfs and the possible turnover towards bluer colours may be a consequence of the presence of sulfide clouds with different thicknesses, the depletion of alcalines, and/or gravity effects.
Key words: stars: low-mass / brown dwarfs / techniques: photometric
© ESO, 2013
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