  Using CCD photometry obtained by the EROS collaboration in 1991-1993, we have
discovered an LMC variable star with a light curve that is oscillating with a
mean period of $\sim 14$ days and an amplitude of $\sim$ 0.3 mag. The
oscillations appear with irregular amplitude variations. The Fourier spectrum
shows that the pulsation of this star is phase locked between two modes of
frequencies $f_0$ and 1.5$\times f_0$. Moreover, this object has strong $H
\alpha$ and $H \beta$ emission lines and neutral lines of Helium that suggest a
spectral type between late O and early B. In a preliminary analysis, we derive
a luminosity of $ L=3.4-3.8L_\odot$ and an effective temperature in the range
$\log(T_{eff}) =3.85-4.2$.
