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. Issue 2 (28th November 2018)

• Record Type: Journal Article
• Authors: David-Uraz, A; Erba, C; Petit, V; Fullerton, A W; Martins, F; Walborn, N R; MacInnis, R; Barbá, R H; Cohen, D H; Maíz Apellániz, J; Nazé, Y; Owocki, S P; Sundqvist, J O; ud-Doula, A; Wade, G A
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 483:Issue 2(2019)
• Page Start: 2814
• Page End: 2824
• Publication Date: 2018-11-28
• Subjects: stars: early-type -- stars: individual: NGC 1624-2 -- stars: magnetic field -- stars: winds, outflows -- ultraviolet: stars; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty3227
• Languages: English
• ISSNs: 0035-8711

Abstract

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.