Measuring strong magnetic fields of neutron stars with the next-generation of X-ray instruments

Abstract

To date, the only direct method to assess the strong magnetic fields of High-Mass X-ray Binaries containing accreting neutron stars is the observation and analysis of electron cyclotron resonance features (short: "cyclotron lines" or CRSFs) in their high-energy X-ray spectra. We dicuss how the upcoming era of new observatories and instrumentation like IXO will change our "magnetic" view of those objects. The science case for IXO in this respect does not focus on the measurement of the cyclotron lines themselves (which are typically at 10–100 keV) but on obtaining new constraints on the accreting sources’ geometries and physical parameters as key ingredients to disentangle their influences and understand the overall timing and spectral properties of neutron star highmass X-ray binaries.