THE STELLAR POPULATION AND STAR-FORMATION IN THE BLUE COMPACT GALAXY SBS-1331+493

The stellar population and evolutionary characteristics (metallicity o f stellar components and stellar ages and mass functions) in the blue compact galaxy SBS 1331+493 are studied; this galaxy has a low heavy-e lement abundance and has experienced bursts of star formation. A new c omposite method for determining the stellar composition of galaxies is proposed. This method incorporates the advantages of both evolutionar y studies and population synthesis. Long-slit spectra obtained on the 4-m telescope of Kitt Peak National Observatory are used for the analy sis. The resulting ages for the last burst of star formation in four c onsecutive spatial zones are from 3.8 x 10(6) to 34 x 10(6) yr, corres ponding to a velocity of 13 +/- 5 km/s for the corresponding wave of s tar formation. The metallicities of the stellar populations [Z/Z.] in different regions are from -0.96 to -0.76. The initial mass function P si(M) similar to M-alpha = 2.36 +/- 0.12 for all the regions studied.