Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-28T14:22:22.254Z Has data issue: false hasContentIssue false
  • English
  • Français

High-exitation nebulae around Magellanic Wolf-Rayet stars

Published online by Cambridge University Press:  01 July 2008

Manfred W. Pakull
Manfred W. Pakull*
Affiliation:
CNRS, Observatoire Astronomique 11, rue de l'Université, F67000 Strasbourg, France email: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The SMC harbours a class of hot nitrogen-sequence Wolf-Rayet stars (WNE) that display only relatively weak broad He ii λ4686 emission indicative of their low mass-loss rates and which are therefore hard to detect. However, such stars are possible emitters of strong He+ Lyman continua which in turn could ionize observable He iii regions, i.e. highly excited H ii regions emitting nebular He ii λ4686 emission. We here report the discovery of a second He iii region in the SMC within OB association NGC 249 within which the weak-lined WN star SMC WR10 is embedded. SMC WR10 is of special importance since it is a single star showing the presence of atmospheric hydrogen. While analysing the spectrum in the framework of two popular, independent WR atmosphere models we found strongly discrepant predictions (by 1 dex) of the He+ continuum for the same input parameters. A second interesting aspect of the work reported here concerns the beautiful MCELS images which clearly reveal a class of strongly O iii λ5007 emitting (blue-coded) nebulae. Not unexpectedly, most of the “blue” nebulae are known Wolf-Rayet bubbles, but new bubbles around a few WRs are also detected. Moreover, we report the existence of blue nebulae without associated known WRs and discuss the possibility that they reveal weak-wind WR stars with very faint stellar He ii λ4686 emission. Alternatively, such nebulae might hint at the hitherto missing population of relatively low-mass, hot He stars predicted by massive binary evolution calculations. Such a binary system is probably responsible for the ionization of the unique He ii λ4686-emitting nebula N 44C.

Keywords

shock wavesstars: windsoutflowsstars: Wolf-RayetISM: bubblesHII regionsMagellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S256: The Magellanic System: Stars, Gas, and Galaxies , July 2008 , pp. 437 - 442
Copyright
Copyright © International Astronomical Union 2009

References

Crowther, P. A. & Hadfield, L. J. 2006, A&A, 449, 711Google Scholar
Dopita, M. A., Bell, J. F., Chu, Y.-H., & Lozinskaya, T. A. 1994, ApJS, 93, 455CrossRefGoogle Scholar
Dufour, R. J. 1989, Rev. Mexicana AyA, 18, 87Google Scholar
Foellmi, C., Moffat, A. F. J., & Guerro, M. A. 2003, MNRAS, 338, 360CrossRefGoogle Scholar
Hamann, W.-R. & Gräfener, G. 2004 A&A, 427, 697 — http://www.astro.physik.uni-potsdam.de/~wrh/PoWR/powrgrid1.htmlCrossRefGoogle Scholar
Massey, P. & Duffy, A. S. 2001, ApJ, 550, 713CrossRefGoogle Scholar
Niemela, V. S., Heathcote, S. A., & Weiller, W. C. 1991, in van der Hucht, K.A. & Hidayat, B. (eds.), Wolf-Rayet stars and interrelations with other massive stars in galaxies, IAU Conf.Proc. 143 (Dordrecht: Kluver), p. 425CrossRefGoogle Scholar
Pakull, M. W. & Motch, C. 1989a, Nature 337, 337CrossRefGoogle Scholar
Pakull, M. W. & Motch, C. 1989b, in Meurs, E. J. A. & Fosbury, R. A. E. (eds.), ESO workshop on extranuclear activity in galaxies (Garching: ESO), p. 285Google Scholar
Pakull, M. W. 1989, in de Boer, K. S., Spite, F., & Stasińska, G. (eds.), Recent developments in Magellanic Cloud research (Meudon: Observatoire de Paris), p. 183Google Scholar
Pakull, M. W. 1991, in van der Hucht, K. A. & Hidayat, B. (eds.), Wolf-Rayet stars and interrelations with other massive stars in galaxies, IAU Conf.Proc. 143 (Dordrecht: Kluver), p. 391CrossRefGoogle Scholar
Pakull, M. W. & Bianchi, L. 1991, in Hucht, K. A. van der & Hidayat, B. (eds.), Wolf-Rayet stars and interrelations with other massive stars in galaxies, IAU Conf.Proc. 143 (Dordrecht: Kluver), p. 260CrossRefGoogle Scholar
Pakull, M. W & Angebault, L. P. 1986, Nature, 322, 511CrossRefGoogle Scholar
Schmutz, W., Leitherer, C., & Gruenwald, R. 1992, PASP, 104, 1164CrossRefGoogle Scholar
Smith, R. C. & the MCELS Team 1999, in Chu, Y.-H., Suntzeff, N., Hesser, J., & Bohlender, D. (eds.), New views of the Magellanic Clouds, IAU Conf.Proc. 190, p. 28 — http://www.ctio.noao.edu/~mcels/CrossRefGoogle Scholar
Smith, L. J., Norris, R. P. F., & Crowther, P. A. 2002, MNRAS, 337, 1309CrossRefGoogle Scholar
Terlevich, R. & Melnick, J. 1985, MNRAS, 213, 841CrossRefGoogle Scholar
Vink, J. S. & de Koter, A. 2005, A&A, 442, 587Google Scholar
Wellstein, S., Langer, N., & Braun, H. 2001, A&A, 369, 939Google Scholar
Yoon, S.-C. & Langer, N. 2005, A&A, 443, 643Google Scholar