High temporal resolution spectroscopic observations of the flare star V1054 Oph

We present the results of a high temporal resolution spectroscopic monitoring of the flare (UV Cet type) star V1054 Oph (Wolf 630AB), classified as a dM3.5e visual binary system. Intermediate resolution spectra have been taken during four nights (2-5 April 2001) using the IDS spectrograph of the 2.5 m Isaac Newton Telescope (INT) (La Palma, Canary Islands, Spain). The V1054 Oph spectra show very strong emission lines even in its quiescent state. The analysis of the temporal evolution of the observed emission lines (from H _β to H ₁₁ and the Ca II H and K lines) reveals four strong flares and several weak flares. We have studied in detail the behaviour of the chromospheric lines during the different phases (pre-flare, impulsive and gradual decay) of these flares. The observed flares last from ∼25 to 95 min. The equivalent width of the H _β line changes by a factor up to ∼2.3. Broad wings and asymmetric (red-shifted) lines are observed as well.