* Astronomy

Title: GTC Osiris spectroscopic identification of a faint L subdwarf in the UKIRT Infrared Deep Sky Survey
Authors: N. Lodieu (1,2), M. R. Zapatero Osorio (3), E. L. Martin (3), E. Solano (3), M. Aberaturi (3) ((1) IAC, Tenerife, Spain (2) University of La Laguna, Tenerife, Spain, (3) Centro de Astrobiologia, CSIC-INTA, Madrid, Spain)

We present the discovery of an L subdwarf in 234 square degrees common to the UK Infrared Telescope (UKIRT) Infrared Deep Sky Survey Large Area Survey Data Release 2 and the Sloan Digital Sky Survey Data Release 3. This is the fifth L subdwarf announced to date, the first one identified in the UKIRT Infrared Deep Sky Survey, and the faintest known. The blue optical and near-infrared colours of ULAS J135058.86+081506.8 and its overall spectra energy distribution are similar to the known mid-L subdwarfs. Low-resolution optical (700-1000 nm) spectroscopy with the Optical System for Imaging and low Resolution Integrated Spectroscopy spectrograph on the 10.4 m Gran Telescopio de Canarias reveals that ULAS J135058.86+081506.8 exhibits a strong KI pressure-broadened line at 770 nm and a red slope longward of 800 nm, features characteristics of L-type dwarfs. From direct comparison with the four known L subdwarfs, we estimate its spectral type to be sdL4-sdL6 and derive a distance in the interval 94-170 pc. We provide a rough estimate of the space density for mid-L subdwarfs of 1.5x10^(-4) pc^(-3).

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