  2RE J0743+224 (BD +23 1799) is a chromospherically active star selected by
X-rays and EUV emission detected in the Einstein Slew Survey and ROSAT Wide
Field Camara (WFC) all sky survey, and classified as single-lined spectroscopic
binary by (Jeffries et al. 1995). We present here high resolution echelle
spectroscopic observations of this binary, obtained during a 10 night run 12-21
January 1998 using the 2.1m telescope at McDonald Observatory. These
observations reveal it is a double-lined spectroscopic binary. A dramatic
increase in the chromospheric emissions (H_alpha and Ca II IRT lines) is
detected during the observations. Several arguments favor the interpretation of
this behavior as an unusual long-duration flare. First the temporal evolution
of the event is similar to the observed in other solar and stellar flares, with
an initial impulsive phase characterized by a strong increase in the
chromospheric lines (the H_alpha EW change in a factor of 5 in only one day)
and thereafter, the line emission decreased gradually over several days.
Second, a broad component in the H_alpha line profile is observed just at the
beginning of the event. Third, the detection of the He I D_{3} in emission and
a filled-in He I 6678 A. We detect a Li I 6708 A line enhancement which is
clearly related with the temporal evolution of the flare. The maximum Li I
enhancement occurs just after the maximum chromospheric emission observed in
the flare. We suggest that this Li I is produced by spallation reactions in the
flare. This is the first time that such LiI enhancement associate with a
stellar flare is reported, and probably the long-duration of this flare is a
key factor for this detection.
