We have presented a sample of 1000 Be star candidates in the Small Magellanic Cloud, giving positions and basic photometric information along with periodicities when present. Many of these objects show apparently new kinds of photometric variability never seen before, and this feature enabled us to carry out an empirical classification based on the light curve appearance. There is evidence that some of these objects are truly Be stars, but spectroscopy is needed to confirm this suspicion. On the other hand, the hypothesis that at least part of the type-1 and type-2 stars are Be-stars with accreting white dwarfs, or alternatively, pre-main sequence stars showing accretion disk instabilities, should be studied more thoroughly.
|Figure 7: The V vs. B-V diagram for the sample stars. Blue dots correspond to type-1 stars, red dots to type-2 stars, green dots to type-3 stars, circles to type-4 stars and black dots to type-1 stars showing high and low states, as type-2 stars. The track of the main sequence (Allen 2000) is shown for reference. Note the sharp cut-off at the blue edge.
|Figure 8: The V-I vs. B-V diagram for the sample stars. The track of the main sequence (Allen 2000) is shown as a reference. Meaning of the symbols are as in Fig. 7.
The understanding of the phenomena causing the photometric variability of the stars discussed in this paper requires knowledge of the spectral energy distributions of these stars. We plan to discuss, in a forthcoming paper, the detailed photometric properties of these objects along with spectroscopic data. It should be interesting to test the accretion scenario for type-1 stars. Since the theory of accretion is rather well developed, it could be a source of physical information about the environments surrounding these objects. We also plan to search the OGLE-II database for Be stars in the Large Magellanic Cloud. It should be interesting to investigate if the same types of light curves are observed in the LMC, whose metallicity is intermediate between the SMC and our Galaxy, and how the light curve properties are modified by the change in metallicity.
This work was supported by Grant Fondecyt 1000324 and DI UdeC 202.011.030-1.0. The authors are very grateful to Professor Bohdan Paczynski for many interesting suggestions on this paper. We would also like to thank the OGLE collaboration for making their data public domain, thus enabling us to carry out this research. We also acknowledge the anonymous referee who made valuable comments to improve a first version of this manuscript.
Copyright ESO 2002