Discovery of Rotational Braking in the Magnetic Helium-strong Star Sigma Orionis E

Type Journal Article
Names R. H. D. Townsend, M. E. Oksala, D. H. Cohen, S. P. Owocki, A. ud-Doula
Publication The Astrophysical Journal
Volume 714
Issue 2
Pages L318-L322
Date May 1, 2010
Library Catalog NASA ADS
Abstract We present new U-band photometry of the magnetic helium-strong star σ Ori E, obtained over 2004-2009 using the SMARTS 0.9 m telescope at Cerro Tololo Inter-American Observatory. When combined with historical measurements, these data constrain the evolution of the star's 1.19 day rotation period over the past three decades. We are able to rule out a constant period at the p null = 0.05% level, and instead find that the data are well described (p null = 99.3%) by a period increasing linearly at a rate of 77 ms per year. This corresponds to a characteristic spin-down time of 1.34 Myr, in good agreement with theoretical predictions based on magnetohydrodynamical simulations of angular momentum loss from magnetic massive stars. We therefore conclude that the observations are consistent with σ Ori E undergoing rotational braking due to its magnetized line-driven wind.
Tags stars: chemically peculiar, stars: individual: HD 37479, stars: magnetic field, stars: mass-loss, stars: massive, stars: rotation
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