Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993mnras.260...21g&link_type=abstract
Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711), vol. 260, no. 1, p. 21-27.
Astronomy and Astrophysics
Astronomy
23
Accretion Disks, Astronomical Models, Emission Spectra, Pulsars, Symbiotic Stars, X Ray Binaries, Balloon-Borne Instruments, Energy Spectra, Neutron Stars, Stellar Magnetic Fields, Stellar Oscillations
Scientific paper
The X-ray pulsar GX 1 + 4 was observed during a balloon flight from Alice Springs, Australia on 1986 November 20. Significant flux was detected over the full energy range of the detector (15-114 keV). The spectrum is very hard with a power-law photon index of 1.85 +/- 0.25. The intensity at 30 keV is (5.1 +/- 0.5) x 10 exp -4/sq cm s keV, a factor of 3 less than typical during the 1970s but orders of magnitude greater than during satellite measurements in 1984 and in early 1987, a few months after the flight. The pulse profiles below 75 keV are very broad and possibly double-peaked. At higher energies there is a remarkable change, with a narrow pulse of phase width 0.1 centered on the phase of the lower energy notch. 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 of about 2 x 10 exp 13 G, a value consistent with accretion models in which the system has a retrograde disk.
Dieters W. B. S.
Greenhill John G.
Sharma Darma P.
Sood Ravi K.
Storey Michelle C.
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