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Monthly Notices Of The Royal Astronomical Society


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.


stars: early-type, stars: individual: NGC 1624-2, stars: magnetic field, stars: winds, outflows, ultraviolet: stars


This article has been published in Monthly Notices of the Royal Astronomical Society. © 2018 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.