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

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

Corresponding author: S. Bagnulo, sbagnulo@eso.org

Received: 5 September 2003
Accepted: 9 December 2003

Abstract

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 . 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  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.