SIMBAD references

The X-ray pulsar A 0535+26 has been observed during its March/April 1989 outburst with the Coded Mask Telescope TTM and the High Energy X-ray Experiment HEXE on board the Mir space station at energies between 4 and 156keV. Pulsed emission (P=103.26s for JD 2447626) has been detected up to at least 100keV. Above 20keV the time averaged pulse profiles show a clear double peak structure with an asymmetric main pulse and a more symmetric secondary pulse. The spectrum of the main pulse is significantly harder than that of the secondary pulse. The phase resolved spectra can only be fitted by a power law with exponential cutoff modified by two absorption lines around 50 and 100keV. We interpret these features as the fundamental and first harmonic cyclotron resonances. The corresponding strength of the magnetic field of the neutron star is 4.3x10¹²Gauss.