SUPERNOVA 1994AJ - A PROBE FOR PRE-SUPERNOVA EVOLUTION AND MASS-LOSS FROM THE PROGENITOR

Extensive photometric and spectroscopic observations of SN 1994aj unti l 540 d after maximum light have been obtained. The photometry around maximum suggests that the SN belongs to the Type TI Linear class, with a peak absolute magnitude of M-V similar to -17.8 (assuming H-0=75 km s(-1) Mpc(-1)). The spectra of SN 1994aj unusual, with the presence o f a narrow line with a P Cygni profile on top of the broad Balmer line emission. This narrow feature is attributed to the presence of a dens e superwind surrounding the SN. At 100-120 d after maximum light the S N ejecta start to interact with this circumstellar material, The SN lu minosity decline rates slowed down [gamma(R)=0.46 mag (100 d)(-1)], be coming less steep than the average late luminosity decline of normal S N II [similar to 1 mag (100 d)(-1)]. This dense ((M) over dot /u(W) si milar to 10(15) g cm(-1)) wind was confined to a short distance from t he progenitor (R-out=similar to 5 x 10(16) cm), and results from a ver y strong mass-loss episode ((M) over dot=10(-3) M. yr(-1)), which term inated shortly before explosion (similar to 5-10 yr).