Abstract The X-ray pulsar GX 1+4 was observed during a balloon flight from Alice Springs, Australia on November 20, 1986. Significant flux was detected over the full energy range of the detector (15 – 114 keV). The spectrum was very hard with a photon power law index of 1.9 ± 0.2. The intensity at 30 keV was (5.1±0.2) × 10−4 cm−2s−1keV−1; a factor of ∼ 3 less than typical during the 1970's but orders of magnitude greater than during recent satellite measurements. The pulse profiles below ∼ 75 keV were very broad with indications of a notch at the peak. At higher energies there was a remarkable change with a narrow pulse of phase width ∼ 0.2 centred on the phase of the lower energy notch. We believe this to be the first observation of phase reversals in pulse profiles in the hard X-ray energy range. The observational evidence can be explained within the framework of a model based on two-photon emission as the dominant continuum source. This requires a magnetic field ∼ 2 × 1013 gauss — a value consistent with accretion models in which the system has a retrograde disc.
Energy spectrum and pulse profiles of the binary pulsar GX 1 + 4
Advances in Space Research ; 11 , 8 ; 35-39
1991-01-01
5 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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