1820017

We propose a 500 ks long INTEGRAL observation of the X-ray pulsar 4U 1626-67 to fully constrain its spectral shape in the hard X-ray band. This X-ray pulsar is rather peculiar among its class as it shows a resonant cyclotron feature at 37 keV (indicating a magnetic field of a few 10E12 G) but the companion mass is a very low-mass star (less than 0.08 Msun). A recent observation made with NuSTAR revealed a complex spectral curvature in the 50-70 keV band that could be accounted for by a moderately broadened absorption line at 61 keV. This could be the second cyclotron harmonic even though its energy is lower than the expected value. INTEGRAL is presently the only observatory able to definitively detect this feature and constrain its parameters. [truncated! Please see actual data for full text]