We report results of a spectral and timing analysis of the poorly studied transient X-ray pulsar 2S 1553 - 542 using data collected with the NuSTAR and Chandra observatories and the Fermi /GBM instrument during an outburst in 2015 .
Properties of the source at high energies ( > 30 keV ) are studied for the first time and the sky position had been essentially improved .
The source broadband spectrum has a quite complicated shape and can be reasonably described by a composite model with two continuum components – a black body emission with the temperature about 1 keV at low energies and a power law with an exponential cutoff at high energies .
Additionally an absorption feature at \sim 23.5 keV is discovered both in phase-averaged and phase-resolved spectra and interpreted as the cyclotron resonance scattering feature corresponding to the magnetic field strength of the neutron star B \sim 3 \times 10 ^ { 12 } G. Based on the Fermi /GBM data the orbital parameters of the system were substantially improved , that allowed us to determine the spin period of the neutron star P = 9.27880 ( 3 ) s and a local spin-up \dot { P } \simeq - 7.5 \times 10 ^ { -10 } s s ^ { -1 } due to the mass accretion during the NuSTAR observations .
Assuming accretion from the disk and using standard torque models we have estimated the distance to the system d = 20 \pm 4 kpc .