Abstract 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 ∼ 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 × 1012 G to 1.3 × 1012 G. This variation implies that the cutoff energy does not provide a reliable measure of the surface magnetic field strength in this system.
The luminosity dependence of the phase-averaged X-ray spectrum of the transient 42 second pulsar EXO 2030+375
Advances in Space Research ; 13 , 12 ; 355-360
1993-01-01
6 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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