Metodieva, Y., Antonova, A., Golev, V., Dimitrov, D., García-Álvarez, D. and Doyle, J. G.

Low-resolution optical spectra of ultracool dwarfs with OSIRIS/GTC

Figure 4. The variation in the whole spectrum of 2MASS J17071830+6439331, and around the Hα emission line (inset).


We present the results of low-resolution optical spectroscopy with OSIRIS/GTC (Optical System for Imaging and Low Resolution Integrated Spectroscopy / Gran Telescopio Canarias) for a sample of ultracool dwarfs. For a subsample of seven objects, based on 2MASS NIR photometric colours, a ’photometric’ spectral type is determined and compared to the results of the optical spectroscopy. For the stars, showing Hα line in emission, equivalent widths were measured, and the ratio of Hα to bolometric luminosity were calculated. We find that two dwarfs show the presence of magnetic activity over long periods, LP 326-21 – quasi-constant-like, and 2MASS J17071830+6439331 – variable.

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Last Revised: 2014 December 10th