EX Lupi is a classical T Tauri star (and the EXor prototype) subject to spo
radic outbursts. The historic record shows that it remains at about V = 13.
2 (or m(pg) = 14.7:) for extended periods, from which it has been observed
to brighten to as much as V = 8.4 (on one occasion in 1955-1956). During 19
93-1994 the star remained slightly above normal minimum, at about V = 12.8,
and from that level rose to three maxima at V = 11.4 and on other occasion
s to about V = 12.0. At minimum light an M0 V absorption spectrum is presen
t. At outburst this spectrum is veiled by a hot continuum (well shown by an
IUE exposure), the equivalent widths of the optical-region emission lines
decrease, and reverse P Cygni absorption components appear at the higher Ba
lmer lines. The outbursts are believed to be due to episodic infall onto th
e M0 star.