2 The data

During four years (1997-2000), about 4.5 and 2 million stars were monitored in the LMC and SMC, respectively, in the course of the OGLE II project (Udalski et al. 1997). Typically, about 400 I and 30 B and V observations were secured for each star. An application of a newly developed photometric pipeline (Wozniak 2000; Zebrun et al. 2001a) to the data, based on the DIA method introduced by Alard & Lupton (1998), resulted in the detection of about 68 000 variable stars (Zebrun et al. 2001b). This catalog, apart from presenting positions and light curves for all its objects, provides in addition cross identifications with objects detected during earlier reductions carried out with Dophot. It should be stressed that the positions of the variable stars obtained with the DIA package were obtained from the variable signal only, and may be in principle quite different, especially in the very crowded regions, from the positions obtained from the Dophot photometry. However, the great majority of variable sources detected with DIA were unambiguously cross-correlated with objects detected with Dophot (Zebrun et al. 2001a).

To carry out our search, we inspected the OGLE II SMC BVI maps, and looked for stars matching the usual luminosities and colours observed in Galactic Be stars. Absolute magnitudes of Be stars based on Hipparcos parallaxes (Wegner 2000) indicate that Be stars of luminosity classes IV-V and III have absolute V-band magnitudes between -4 and 0. However, Garmany & Humphreys (1985) report on a population of extremely luminous non-supergiant Be stars in the Magellanic Clouds with absolute V-band magnitudes up to -6. Therefore, we searched for stars having absolute V-band magnitudes between -6 and 0. Assuming a distance modulus for the SMC of  $19.0 \pm 0.2$ mag, a visual extinction of 0.3 mag and a typical amplitude of the photometric variations of Be stars of 0.2 mag, the above absolute magnitudes imply apparent V-band magnitudes between 13.1 and 19.7. In addition to this magnitude constraint, we required that the selected stars should have colours in the range in which Galactic Be stars are usually found, viz.  -0.4 < B-V < 0.6 and -0.35 <V-I < 0.8. Using these criteria, we obtained a first sample of 5168 Be star candidates in our database. As a next step, we extracted the I-band light curves for each of these objects from the OGLE II catalog of variable stars (Zebrun et al. 2001b). The light curves were visually inspected and spurious variables, Cepheids and eclipsing binaries rejected. We then proceeded in classifying the remaining 1056 stars according to the appearance of their light curves. Our set of Be star candidates is likely to be complete for stars showing a rms larger than 0.02 mag in the I band. However, we could have missed Be stars either not showing long-term variations, or with I-band amplitudes less than 0.02 mag.