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
A. David-Uraz, C. Erba, V. Petit, A. W. Fullerton, F. Martins, N. R. Walborn, R. MacInnis, R. H. Barbá, David H. Cohen, J. Maíz Apellániz, Y. Nazé, S. P. Owocki, J. O. Sundqvist, A ud-Doula, and G. A. Wade.
"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".
Monthly Notices Of The Royal Astronomical Society.