The discovery and study of the optical counterparts of the transient X-raypulsars RX J0052.1-7319 and XTE J0111.2-7317 in the SMC

We report on the discovery and confirmation of the optical counterparts of the two transient X-ray pulsars, RX J0052.1-7319 and XTE J0111.2-7317. In t he narrow ( similar to 300 radius) X-ray error circle of RX J0052.1-7319 we found a V = 14.6 (B - V = 0.1) 09.5IIIe (a classification as a B0Ve star i s also possible, since the luminosity class depends on the uncertainty on t he adopted reddening). Medium resolution spectra for this object show Balme r lines in emission with an equivalent width of H alpha = -12 divided by -1 6 Angstrom. In the X-ray error box of XTE J0111.2-7317 we found a relativel y bright object (V = 15.4, B - V = 0.06) which has been classified as a B0. 5-B1Ve star and that was later confirmed by Coe et al. (2000) as the most p lausible counterpart for XTE J0111.2-7317. Also in this case we easily dete ct Balmer emission lines with an H alpha equivalent width of about -21 Angs trom. There is also evidence for the presence of a surrounding nebula, poss ibly a supernova remnant. A further bright B0Ve star was found just outside the X-ray error circle of XTE J0111.2-7317. We discuss the implication of these results in the light of the current knowledge of Be/X-ray binary syst ems in the Magellanic Clouds and within our Galaxy.