FAST OSCILLATIONS IN THE X-RAY LIGHT CURVE OF η CARINAE

eta Carinae is a binary system formed by two massive stars, loosing mass through strong winds. The wind-wind interactions originate shocks that rise the plasma temperature to 10(6-8) K, producing X-ray emission. Although the overall shape of the light curve can be explained and it is used to calculate the orbital eccentricity, the observed short quasi-periodic oscillations have not been explained yet. In our work we propose that these oscillations are produced by the nutation of the rotation axis of eta Carinae, which is not be perpendicular to the orbital plane. Since in eta Carinae, both the mass loss rate and the wind velocity are latitude dependent, the intensity of the emitted X-rays will be a function of the latitude at which the stellar surface intercepts the orbital plane. By assuming an angle of about 30 degrees between the rotation axis and the perpendicular to the orbital plane, an nutation amplitude of about 5 degrees and a nutation period of 22 days, we were able to reproduce very well the observed X-ray light curve.