  We report on an observation of the low-mass X-ray binary 4U1626-67 performed
during the BeppoSAX Science Verification Phase. An absorption feature at ~37
keV, attributable to electron cyclotron resonance, has been discovered in its
pulse averaged spectrum. The inferred neutron star magnetic field strength is
3.2 (1+z) x 10E12 G, where z is the gravitational redshift. The feature is deep
and narrow and is resolved in both the broad-band fit and in the ratio of
observed counts to those seen from the Crab. The cyclotron resonance energy is
in good agreement with the empirical relation between cyclotron energy and high
energy cutoff, while its width is in agreement with the expected Doppler
broadening of thermal electrons at the cyclotron resonance frequency. The
broad-band 0.1-200 keV spectrum is well fit by a two-component model: a 0.27
+/- 0.02 keV blackbody and a power law with a photon index of 0.89 +/- 0.02.
This is the first broad-band observation made after the change from spin-up to
spin-down that occurred in mid 1990: it confirms the harder spectrum with
respect to those observed in the 2-10 keV range.
