INITIAL MASS FUNCTIONS FROM ULTRAVIOLET STELLAR PHOTOMETRY - A COMPARISON OF LUCKE AND HODGE OB ASSOCIATIONS NEAR 30-DORADUS WITH THE NEARBY FIELD

UV stellar photometry is presented for 1563 stars within a 40' circula r field in the LMC, excluding the 10' x 10' field centered on R136 inv estigated earlier by Hill et al. (1993). Magnitudes are computed from images obtained by the Ultraviolet Imaging Telescope in bands centered at 1615 angstrom and 2558 angstrom. Stellar masses and extinctions ar e estimated for the stars in associations using the evolutionary model s of Schaerer et al. (1993), assuming the age is 4 Myr and that the lo cal LMC extinction follows the Fitzpatrick (1985) 30 Dor extinction cu rve. The estimated slope of the initial mass function (IMF) for massiv e stars (> 15 M.) within the Lucke and Hodge (LH) associations is GAMM A = - 1.08 +/- 0.2. Initial masses and extinctions for stars not withi n LH associations are estimated assuming that the stellar age is eithe r 4 Myr or half the stellar lifetime, whichever is larger. The estimat ed slope of the IMF for massive stars not within LH associations is GA MMA = - 1.74 +/- 0.3 (assuming continuous star formation), compared wi th GAMMA = - 1.35, and GAMMA = - 1.7 +/- 0.5, obtained for the Galaxy by Salpeter (1955) and Scalo (1986), respectively, and GAMMA = - 1.6 o btained for massive stars in the Galaxy by Garmany, Conti, & Chiosi (1 982). The shallower slope of the association IMF suggests that not onl y is the star formation rate higher in associations, but that the loca l conditions favor the formation of higher mass stars there. We make n o corrections for binaries or incompleteness.