New observations of NGC 1624−2 reveal a complex magnetospheric structure and underlying surface magnetic geometry
Alexandre David-Uraz, V. Pétit, M. E. Shultz, A. W. Fullerton, C. Erba, Z. Keszthelyi, Shaquann Seadrow, G. A. Wade
Abstract
ABSTRACT NGC 1624−2 is the most strongly magnetized O-type star known. Previous spectroscopic observations of this object in the ultraviolet provided evidence that it hosts a large and dense circumstellar magnetosphere. Follow-up observations obtained with the Hubble Space Telescope not only confirm that previous inference, but also suggest that NGC 1624−2’s magnetosphere has a complex structure. Furthermore, an expanded spectropolarimetric time series shows a potential departure from a dipolar magnetic field geometry, which could mean that the strongest field detected at the surface of an O-type star is also topologically complex. This result raises important questions regarding the origin and evolution of magnetic fields in massive stars.