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New line-blanketed model atmospheres and their impact on synthesis models

Published online by Cambridge University Press:  26 May 2016

Linda J. Smith ,
Richard P.F. Norris  and
Paul A. Crowther
Linda J. Smith
Affiliation:
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
Richard P.F. Norris
Affiliation:
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
Paul A. Crowther
Affiliation:
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Abstract

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A new grid of ionizing fluxes for O-type and Wolf-Rayet stars is presented for use with evolutionary synthesis codes and analyses of single star H ii regions. A total of 230 expanding, non-LTE, line-blanketed model atmospheres have been calculated for five metallicities (0.05, 0.2, 0.4, 1 and 2 Z⊙). We have used the wm-basic code of Pauldrach et al. (2001) for O-type stars and the cmfgen code of Hillier & Miller (1998) for WR stars. The stellar wind parameters are scaled with metallicity for both O-type and WR stars. The ionizing fluxes of the new models, incorporated into the evolutionary synthesis code STARBURST99 (Leitherer et al. 1999), are compared with the predictions of the original starburst99 and Schaerer & Vacca (1998) for an instantaneous burst. We find large changes in the output ionizing fluxes as a function of age, especially below the He+ edge. In contrast to previous studies, nebular He ii λ4686 will be at, or just below, the detection limit in low metallicity starbursts during the WR phase. The new models have lower fluxes in the He i continuum for Z ≥ 0.4 Z⊙ and ages ≤ 7 Myr because of the increased line-blanketing. The accuracy of the new model atmosphere grid is tested by constructing photo-ionization models for an H ii region where the ionizing flux is provided by an instantaneous burst. The new models occupy the same region in nebular diagnostic diagrams as the observational data of Bresolin et al. (1999), particularly during the WR phase. The new model grid and updated starburst99 code can be downloaded from http://www.star.ucl.ac.uk/starburst.

Type
Part 4. Feedback from Massive Stars
Information
Symposium - International Astronomical Union , Volume 212: A Massive Star Odyssey: From Main Sequence to Supernova , 2003 , pp. 604 - 611
Copyright
Copyright © Astronomical Society of the Pacific 2003 

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