Preprint Logo P34 January
1999


To be published in:
Astronomy & Astrophysics

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

D. Hutsemékers1,*


1 Institut d'Astrophysique et de Géophysique - Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium

* Chercheur Qualifié FNRS, Belgium

+ Based in part on observations collected at the European Southern Observatory (ESO, La Silla)


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: early-type - Stars: Wolf-Rayet - Circumstellar matter - ISM: magnetic fields - SN1987A

Files
Article: lbvori.ps.gz (89617 bytes): HTTP FTP (ftp://vela.astro.ulg.ac.be/preprints/)


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