1 research outputs found
Precession and Nutation in the eta Carinae binary system: Evidences from the X-ray light curve
It is believed that eta Carinae is actually a massive binary system, with the
wind-wind interaction responsible for the strong X-ray emission. Although the
overall shape of the X-ray light curve can be explained by the high
eccentricity of the binary orbit, other features like the asymmetry near
periastron passage and the short quasi-periodic oscillations seen at those
epochs, have not yet been accounted for. In this paper we explain these
features assuming that the rotation axis of eta Carinae is not perpendicular to
the orbital plane of the binary system. As a consequence, the companion star
will face eta Carinae on the orbital plane at different latitudes for different
orbital phases and, since both the mass loss rate and the wind velocity are
latitude dependent, they would produce the observed asymmetries in the X-ray
flux. We were able to reproduce the main features of the X-ray light curve
assuming that the rotation axis of eta Carinae forms an angle of 29 degrees
with the axis of the binary orbit. We also explained the short quasi-periodic
oscillations by assuming nutation of the rotation axis, with amplitude of about
5 degrees and period of about 22 days. The nutation parameters, as well as the
precession of the apsis, with a period of about 274 years, are consistent with
what is expected from the torques induced by the companion star.Comment: 9 pages, 8 figures, MNRAS accepte