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.
@article{arxiv.1412.2736,
title = {Low-resolution optical spectra of ultracool dwarfs with OSIRIS/GTC},
author = {Yanina Metodieva and Antoaneta Antonova and Valeri Golev and Dinko Dimitrov and David García-Álvarez and John Gerard Doyle},
journal= {arXiv preprint arXiv:1412.2736},
year = {2014}
}
Comments
7 pages, 4 figures, 3 tables. arXiv admin note: text overlap with arXiv:astro-ph/0612604 by other authors