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tokens: 2.2 GTC spectroscopy Candidates have been followed up with optical spectroscopy using the Optical System for Imaging and low-Resolution Integrated Spectroscopy (OSIRIS; Cepa et al. 2000 ) instrument on the Gran Telescopio Canarias (GTC) since 2012. Table 2 shows a summary of our GTC spectroscopic observations. The spectra were mostly obtained using the R500R grism, with three making use of the R300R grism. These provide resolving power of around 500 and 300, respectively. The spectra were reduced using standard procedures with IRAF 1 . The HgAr, Ne, and Xe arcs were used on the wavelength calibration of our spectra. Spectral flux calibrations were achieved with standard stars (Oke 1974 , 1990 ; Hamuy et al. 1994 ; Bohlin, Colina Finley 1995 ). Spectral features caused by telluric absorptions in these spectra were not corrected. Five objects were observed twice to gain additional exposure time, and for the purposes of this paper we combined the spectra of these objects from both epochs. Table 2. Summary of the characteristics of the spectroscopic observations made with the OSIRIS on the GTC. R500R and R300R grisms cover a wavelength range of 480–1020nm. A 0.8 arcsec slit used for all observations. Note . References for flux calibration standard stars are 1. Bohlin et al. ( 1995 ); 2. Hamuy et al. ( 1994 ); 3. Oke ( 1974 ); 4. Oke ( 1990 ). 2.3 VLT spectroscopy We have also obtained optical-NIR spectroscopy of five of our candidates, a known sdL8 subdwarf and three radial velocity standard L dwarfs using the X-shooter spectrograph (Vernet et al. 2011 ) on the Very Large Telescope (VLT) since 2014. Table 3 shows a summary of our VLT spectroscopic observations. These X-shooter spectra were observed in an ABBA nodding mode with a 1.2 arcsec slit providing a resolving power of 6700 in the VIS arm and 4000 in the NIR arm. These spectra were reduced with ESO Reflex in a lazy mode (Freudling et al. 2013 ). The flat field used for the science data was also used for flat-fielding the flux standard star spectrum (by set flat strategy to false). Telluric corrections were achieved for both VIS and NIR arms using telluric standards that were observed right after or before our targets at a very close airmass. To extract telluric spectra for correction, we fitted and normalized spectra of telluric standards stars to their continuum and removed non-telluric features (e.g. hydrogen absorption lines) with iraf splot . These X-shooter spectra were smoothed by 101 and 51 pixels in the VIS and NIR arms, respectively, for display in figures, which reduced the resolving power to about 600 and increased their signal-to-noise ratio (SNR per pixel) by 10 and 7 times. Table 3. Summary of the characteristics of the spectroscopic observations made with X-shooter. Wavelength ranges for the VIS and NIR arms are 530–1020 and 990–2480 nm. 1.2 arcsec slits are used for both VIS and NIR arms. DENIS-P J025503.3−470049, 2MASS J08354256−0819237, and DENIS-P