A ~ 14 Days Star with Two Phase-Locked Modes of Pulsation in the Eros Database

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 $\log(T_{eff}) =3.85-4.2$.