Poster Abstracts

Name/Affiliation:  Antoaneta Antonova (Dept. of Astronomy, St. Kl. Ohridski University of Sofia)

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

In a pilot project including ultracool dwarfs and late-M candidates from the 2MASS database, we have obtained low-resolution spectra with the OSIRIS instrument at the Gran Telescopio Canarias (GTC), La Palma. As a result, the 7 late-M dwarf candidates were spectrally classified and H alpha equivalent widths were measured. The ratio of H alpha to bolometric luminosity was calculated. The latter is the most common characteristic of magnetic activity in cool stars. The M8.5 dwarf LP 326-21 showed consistent levels of emission, as compared to those in the literature, while 2MASS 1707+64, also M 8.5, showed variable levels of H alpha emission as found in previous studies.