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Astron. Astrophys. 344, 143-150 (1999)

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The orientation within the Galaxy and the Large Magellanic Cloud of nebulae ejected by massive stars *

D. Hutsemékers **

Institut d'Astrophysique, Université de Liège, 5 av. de Cointe, B-4000 Liège, Belgium

Received 27 April 1998 / Accepted 5 January 1999

Abstract

The orientation of nebulae ejected by massive stars (Luminous Blue Variables, WR stars, SN1987A) is investigated with respect to the structure of the galaxy to which they belong.

In the Galaxy, we find that the projected long axes of the nebulae most often align with the galactic plane, and then also with the galactic magnetic field. This alignment is statistically significant. In addition, a few nebulae are apparently oriented perpendicular to the galactic plane. In the Large Magellanic Cloud, the nebular axes are found to closely follow the spiral magnetic field. With different inclinations, the Galaxy and the Large Magellanic Cloud probably offer complementary views of the same phenomenon.

Although the sample studied thus far is small and the statistics limited, these results suggest that the orientation of massive star ejecta depends on galactic magnetic fields.

Since the nebular axes are apparently correlated to the symmetry axes of the stars themselves, and since, in the early evolutionary stages, alignments of accretion disk axes with the interstellar magnetic field have been reported, it is argued that the observed alignment effect results from the star formation process.

Key words: stars: circumstellar matter – stars: early-type – stars: supernovae: individual: SN 1987A – stars: Wolf-Rayet – ISM: magnetic fields – galaxies: Magellanic Clouds

* Based in part on observations collected at the European Southern Observatory (ESO, La Silla)
** Also, Chercheur Qualifié au Fonds National de la Recherche Scientifique (FNRS Belgium)

Correspondence to: hutsemek@astro.ulg.ac.be

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© European Southern Observatory (ESO) 1999

Online publication: March 10, 1999
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