An important physical parameter of neutron stars (NSs) is the strength B of their
surface magnetic field (MF), because the mechanisms of their accretion and X-ray
emission are strongly affected by the values of B. Accurate estimates of B of accreting
NSs are available through detections of cyclotron resonance scattering features (CRSFs)
in their X-ray spectra. However, the current observational sensitivity limits the CRSF
detections to 100 keV, and hence B 1013 G. As an alternative method to estimate B
(particularly towards higher values) of accreting NSs, the classical accretion torque
theory by Ghosh and Lamb (1979), hereafter GL79, has been revived, calibrated, and
applied to several high-mass X-ray binaries (HMXBs). The content of this seminar is as
follows: (1) Why am I searching for highly-magnetized NSs in binary systems? (2) How to
estimate the surface MF of NSs? (3) Application of the GL79 model to the
accretion-powered X-ray pulsar IGR J00370+6122.