A multispectral view of the periodic events in eta Carinae

DAMINELI, A.; HILLIER, D.J.; CORCORAN, M.F.; STAHL, O.; GROH, J.H.; ARIAS, J.; TEODORO, M.; MORRELL, N. I.; GAMEN, R. C.; GONZALEZ, F.; LEISTER, N.V.; LEVATO, H.; LEVENHAGEN, R.S.; GROSSO, M.; COLOMBO, J.F.A.; WALLERSTEIN, G.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Año: 2008 vol. 386 p. 2330 - 2344

0035-8711

A full description of the 5.5-yr low excitation events in η Carinae is presented. Weshow that they are not simple and brief, as thought before, but a combination of twocomponents. The first, the ‘slow variation’ component, is revealed by slow changes in the ionization level of circumstellar matter across the whole cycle and is caused bythe gradual immersion of the secondary star in the wind of the primary. The second,the ‘collapse’ component, is restricted to some months around the minimum, and isdue to the immersion of the secondary deep in the primary wind. During this stagethere is a general collapse of the wind-wind collision shock, and the Weigelt blobs are strongly shielded from high energy photons (E > 16 eV). High energy phenomenaare sensitive only to the ‘collapse’, low energy only to the ‘slow variation’ and thatof intermediate energy to both components. Simple eclipses and mechanisms effective only near periastron (e.g., shell ejection or accretion onto the secondary star) cannot account for the 5.5-yr cycle.     We find anti-correlated changes in the intensity and the radial velocity of P Cygniabsorption profiles in Fe ii λ6455 and He i λ7065 lines, indicating that the former isassociated to the primary and the later to the secondary star. We present a set of light curves representative of the whole spectrum, indicating the spatial location where they are formed.