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

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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 14 days and an amplitude of 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 f₀ and 1.5× f₀. Moreover, this object has strong H α and H β 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 and an effective temperature in the range (Teff) =3.85-4.2.