A multispectral view of the periodic events in Eta Carinae

A. DAMINELI, D. J. HILLIER, M. F. CORCORAN, O. STAHL, J. H. GROH, J. ARIAS, M. TEODORO, N. MORRELL, R. GAMEN, F. GONZALEZ, N. V. LEISTER, J.F ALBACETE-COLOMBO, H. LEVATO,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Blackwell publishing

Lugar: London, UK; Año: 2008 vol. 1 p. 2330 - 2344

0035-8711

A full description of the 5.5-yr low excitation events in Eta-Carinae is presented. We show thatthey are not as simple and brief as previously thought, but a combination of two components.The first, the slow variation component, is revealed by slow changes in the ionization levelof circumstellar matter across the whole cycle and is caused by gradual changes in the wind–wind collision shock-cone orientation, angular opening and gaseous content. The second,the collapse component, is restricted to around the minimum, and is due to a temporaryglobal collapse of the wind–wind collision shock. High-energy photons (E > 16 eV) from thecompanion star are strongly shielded, leaving the Weigelt objects at low-ionization state formore than six months. High-energy phenomena are sensitive only to the collapse, low energyonly to the slow variation and intermediate energies to both components. Simple eclipses andmechanisms effective only near periastron (e.g. shell ejection or accretion on to the secondarystar) cannot account for the whole 5.5-yr cycle.   We find anti-correlated changes in the intensity and the radial velocity of P Cygni absorptionprofiles in Fe II 6455 and He I 7065 lines, indicating that the former is associated to theprimary and the latter to the secondary star. We present a set of light curves representative ofthe whole spectrum, useful for monitoring the next event (2009 January 11).