1998A&A...338L..79C

We report the detection of a cyclotron absorption line and its second harmonic in the average spectrum of the high mass X-ray binary 4U 1907+09 observed by the BeppoSAX satellite on 1997 September 27 and 28. The broad band spectral capability of BeppoSAX allowed a good determination of the continuum against which the two absorption features are evident at ∼19 and ∼39keV. Correcting for the gravitational redshift of a ∼1.4M_☉ neutron star, the inferred surface magnetic field strength is B_surf = 2.1x10¹² G that is typical for this kind of systems. We also detected an iron emission line at ∼6.4keV, with an equivalent width of ∼60eV.