Optical identification of EUV sources: the secrets of EUVE J2056-17.1.
Doyle, J. G.; Mathioudakis, M.; Dupuis, J.; Drake, J. J.; Fruscione, A.; Kilkenny, D.; Christian, C. A.; Sirk, M. M.; Craig, N.; Abbott, M. J.
Abstract
We present optical, ultraviolet (UV), and extreme ultraviolet (EUV) results for a new active late-type dwarf star discovered by the Extreme Ultraviolet Explorer (EUVE). A large flare with an energy in excess of 10^35^erg and duration of ~1.1 days was detected in the EUVE Lex/B band (60-200A). The energetics of the event indicate that radiative losses in the EUV are a significant contributor to the energy budget in stellar flares. The "quiescent" EUV emission of the source is similar to the most active flare stars with the "quiescent" optical spectrum showing strong Hα, Ca II H & K, and Mg II h & k emission. A strong Li I 6707.8A absorption line is also present in the spectrum. We have estimated a Li abundance of log N(Li)=2.5+/-0.4. Although the high Li abundance suggests that EUVE J2056-17.1 is a young object having recently arrived on the main sequence; the high flare activity favours an interpretation where the enhanced Li is sustained by spallation reactions.