Journal Article

A multispectral view of the periodic events in <b><i>η</i></b> 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, H. Levato, R. S. Levenhagen, M. Grosso, J. F. Albacete Colombo and G. Wallerstein

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 386, issue 4, pages 2330-2344
Published in print June 2008 | ISSN: 0035-8711
Published online April 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13214.x
A multispectral view of the periodic events in η Carinae★†‡§¶

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A full description of the 5.5-yr low excitation events in η Carinae is presented. We show that they 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 level of 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 temporary global collapse of the wind–wind collision shock. High-energy photons (E > 16 eV) from the companion star are strongly shielded, leaving the Weigelt objects at low-ionization state for more than six months. High-energy phenomena are sensitive only to the collapse, low energy only to the slow variation and intermediate energies to both components. Simple eclipses and mechanisms effective only near periastron (e.g. shell ejection or accretion on to the secondary star) cannot account for the whole 5.5-yr cycle.

We find anti-correlated changes in the intensity and the radial velocity of P Cygni absorption profiles in Fe iiλ6455 and He iλ7065 lines, indicating that the former is associated to the primary and the latter to the secondary star. We present a set of light curves representative of the whole spectrum, useful for monitoring the next event (2009 January 11).

Keywords: stars: general; stars: individual: η Carinae

Journal Article.  13880 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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