New observations of NGC 1624-2 reveal a complex magnetospheric structure and underlying surface magnetic geometry
Wade, G. A.; Fullerton, A. W.; Shultz, M. E.; Petit, V.; Keszthelyi, Z.; Erba, C.; David-Uraz, A.; Seadrow, S.
United States, Netherlands, Canada
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.