We report on the evolution in the X-ray spectrum of the transient X-ray pulsar EXO 2030+375 during part of an outburst in 1985 May-August. The overall continuum spectral shape is similar to that of other accreting pulsars and can be represented by a power-law spectrum modified at low energies by significant absorption and at high-energies either by an exponential cut-off or by the effects of cyclotron scattering. As the luminosity decreased by a factor of approximately 100, the X-ray spectrum became harder with the photon index decreasing from 1.83 +/- 0.01 to 1.29 +/- 0.01. In addition, the high-energy cutoff decreased from 20 to 10 keV during the same interval. If the cutoff is interpreted in terms of cyclotron resonance scattering, then this implies a magnetic field strength that decreased from 2.6 x 10(exp 12) G to 1.3 x 10(exp 12) G. This variation implies that the cutoff energy does not provide a reliable measure of the surface magnetic field strength in this system.


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    Title :

    The luminosity dependence of the phase-averaged X-ray spectrum of the transient 42 second pulsar EXO 2030+375


    Contributors:

    Published in:

    Publication date :

    1993-12-01



    Type of media :

    Miscellaneous


    Type of material :

    No indication


    Language :

    English


    Keywords :



    The Luminosity Dependence of the Phase-Averaged X-Ray Spectrum of the Transient 42 Second Pulsar EXO 2030+375

    Parmar, A. N. / Reynolds, A. P. / White, N. E. et al. | British Library Conference Proceedings | 1993



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