Journal Article

Scandium and chromium in the strontium filament in the Homunculus of η Carinae

M. A. Bautista, C. Ballance, T. R. Gull, H. Hartman, K. Lodders, M. Martínez and M. Meléndez

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 393, issue 4, pages 1503-1512
Published in print March 2009 | ISSN: 0035-8711
Published online February 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.14246.x
Scandium and chromium in the strontium filament in the Homunculus of η Carinae

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We continue a systematic study of chemical abundances of the strontium filament found in the ejecta of η Carinae. To this end we interpret the emission spectrum of Sc ii and Cr ii using multilevel non-local thermodynamic equilibrium models. Since the atomic data for these ions were previously unavailable, we carry out ab initio calculations of radiative transition rates and electron impact excitation rate coefficients. The observed spectrum is consistent with an electron density of the order of 107 cm−3 and a temperature between 6000 and 7000 K, conditions previously determined from [Ni ii], [Ti ii] and [Sr ii] diagnostics. The observed spectrum indicates an abundance of Sc relative to Ni more than 40 times the solar value, while the Cr/Ni abundance ratio is roughly solar. Various scenarios of depletion and dust destruction are suggested to explain such abnormal abundances.

Keywords: atomic data; atomic processes; line: formation; stars: abundances

Journal Article.  5847 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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