Optical identification of EUV sources: The secrets of EUVE J2056-17.1

M. Mathioudakis, J.J. Drake, N. Craig, D. Kilkenny, J.G. Doyle, M.M. Sirk, J. Dupuis, A. Fruscione, C.A. Christian and M.J. Abbott

Astron. Astrophys. (in press) April 1995

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 1E35 erg and duration of ~1.1 days was detected in the EUVE Lex/B band (60--200AA). The energetics of the event indicate that radiative losses in the EUV is 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 H alpha, Ca II H&K Mg II h&k emission and Li I 6707.8A absorption. We have estimated a Li abundance of log N(Li) = 2.5+-0.4. Although the high Li abundance suggests that EUVEJ2056-17.1 is a young object recently arrived on the main sequence, the high flare activity favors an interpretation where the enhanced Li is sustained by spallation reactions.
Key Words:stars: flare--stars: late-type--EUV emission