We have selected all the stars from the colour magnitude diagram (see
Paper I, Fig. 3) for which we do not have spectroscopic data and which
were in the range V <= 13.3 and (B - V)_0_ <= 0 (where (B - V)_0_ is the
intrinsic colour estimated using the data in Table 3). Effective
temperatures were estimated by fitting a cubic to the T_eff_ -(B - V)_0_
results in Table 5 (assuming that log g = 4.0). We then calculated
bolmetric luminosities and masses using the method employed in Sect. 3.5.
Thirty six stars were selected, all with masses in the range 3-10 M_sun_.
There is also one confirmed red supergiant cluster member of NGC3293 which
must be included. Feast (1958) gives an M0Iab classification with MV =
-5.9 and using the bolometric corrections of Elias et al. (1985), we have
estimated a mass from the Geneva evolutionary tracks of 15 M_sun_.
To determine the IMF, we follow the method of Hillenbrand et al.
(1993) and Massey et al. (1995), so that our results can be directly
compared to those studies. Stars were divided into mass bins, whose size
was chosen to give comparable numbers of objects as far as possible. The
number of stars in each bin was normalised to unit logarithmic mass
interval and to unit area (kpc2) and the Scalo (1986) notation was
adopted. The area sampled was taken from the cluster radius (we used twice
the quoted radius, to be consistent with the membership criteria applied
In Fig. 7 we plot the present day mass function (PDMF), which given
the relatively small age of NGC3293 and the fact that the majority of
stars are on the main-sequence, is effectively the IMF. A linear least
squares fit was performed, with each point being weighted by sqrt N, where
N is the number of points in the bin. We find a slope of Gamma = -1.5 +-
0.2 over the range 2.8-40 M_sun_. Baume et al. (2003) estimate Gamma =
-1.2 for th mass range 1.4-45 M_sun_, but find a steeper slope of Gamma =
-1.6 for the higher mass stars in the range 8-45 M_sun_. Our results imply
that this steeper value for the high mass objects extends down to ~3
M_sun_ and are consistent with the range of IMFs found by Massey et al.
(1995) for young clusters in the Northern Milky Way.
Coarse cluster. D. O. Mills Reflector, Santiago, Chile.