Extreme resonance line profile variations in the ultraviolet spectra of NGC 1624-2: Probing the giant magnetosphere of the most strongly magnetized known O-type star

A. David-Uraz, C. Erba, V. Petit, A. W. Fullerton, F. Martins, N. R. Walborn, R. MacInnis, R. H. Barba, D. H. Cohen, J. Máiz Apellaniz, Y. Naze, S. P. Owocki, J. O. Sundqvist, A. Ud-Doula, G. A. Wade

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Abstract

In this paper, we present high-resolution HST/COS observations of the extreme magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of this archetypal object. We examine the variability of its wind-sensitive resonance lines, comparing it to that of other known magnetic O stars. In particular, the observed variations in the profiles of the C IV and Si IV doublets between low state and high state are the largest observed in any magnetic O-type star, consistent with the expected properties of NGC 1624-2's magnetosphere. We also observe a redshifted absorption component in the low state, a feature not seen in most stars. We present preliminary modelling efforts based on the Analytic Dynamical Magnetosphere (ADM) formalism, demonstrating the necessity of using non-spherically symmetric models to determine wind/magnetospheric properties of magnetic O stars.

Original languageEnglish (US)
Pages (from-to)2814-2824
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume483
Issue number2
DOIs
StatePublished - Feb 21 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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