EDP Sciences
Free access
Volume 416, Number 3, March IV 2004
Page(s) 1149 - 1158
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20034283

A&A 416, 1149-1158 (2004)
DOI: 10.1051/0004-6361:20034283

Discovery of a huge magnetic field in the very young star NGC 2244-334 in the Rosette Nebula cluster

S. Bagnulo1, H. Hensberge2, J. D. Landstreet3, T. Szeifert1 and G. A. Wade4

1  European Southern Observatory, Casilla 19001, Santiago 19, Chile
    e-mail: tszeifer@eso.org
2  Royal Observatory of Belgium, Ringlaan 3, 1180 Brussel, Belgium
    e-mail: Herman.Hensberge@oma.be
3  Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada
    e-mail: jlandstr@astro.uwo.ca
4  Department of Physics, Royal Military College of Canada, PO Box 17000, Station "Forces", Kingston, Ontario K7K 7B4, Canada
    e-mail: Gregg.Wade@rmc.ca

(Received 5 September 2003 / Accepted 9 December 2003 )

During a survey of field strengths in upper main sequence stars in open clusters, we observed the star NGC 2244-334 in the Rosette Nebula cluster and discovered an extraordinarily large mean longitudinal field of about  -9 kG, the second largest longitudinal field known in a non-degenerate star. This star appears to be a typical Ap He-wk (Si) star of about  $4~M_\odot$. Spectrum synthesis using a line synthesis code incorporating the effects of the strong magnetic field indicates that He is underabundant by about 1.5 dex, and C, O and Mg by about 0.1-0.4 dex, while Si, Mn and Fe are overabundant by about 1 dex, and Cr and Ti are nearly 2 dex overabundant.

Cluster membership for this star is secure, so its age is about $2\times 10^6$ yr, which is less than 3% of its main sequence lifetime. This star is one of the very youngest magnetic upper main sequence stars with a well-determined age, and confirms that both magnetic fields and strong chemical peculiarity can appear in stars which are both extremely young and very close to the ZAMS.

Key words: polarization -- stars: abundances -- stars: chemically peculiar -- stars: magnetic fields -- stars: individual: NGC 2244-334

Offprint request: S. Bagnulo, sbagnulo@eso.org

SIMBAD Objects

© ESO 2004