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Title: Detection of a very low hard X-ray pulse fraction in the bright state of GX 1+4
Authors: Rao, A.R.
Paul, Biswajit
Chitnis, V.R.
Agrawal, P.C.
Manchanda, R.K.
Issue Date: Sep-1994
Publisher: EDP Sciences
Citation: Astronomy and Astrophysics, 1994, Vol.289, pL43-L46
Abstract: We have observed the Galactic center hard X-ray pulsar GX 1+4 on 1993 December 11, in the energy range of 20 - 100 keV with a balloon-borne Xenon filled Multi-cell Proportional Counter (XMPC) telescope. The source was detected in a bright state, the average observed source count rate being 10.1 +/- 0.2/s per detector. X-ray pulsations with a period of 121.0 +/- 0.4 s were detected in the source at a very high significance level. This, compared with the Burst and Transient Source Experiment (BATSE) observations, gives a spin down rate of dot-P = 1.6 +/- 1.4 s/yr. The pulse fraction in the hard X-ray range is low (35%), and the observed spectrum is very hard (power law energy index 0.54 +/- 0.18). The observed source luminosity in the 20 - 100 keV range is 7.9 +/- 0.3 x 1037 erg/s. These properties are similar to those seen during high luminosity spin up state of early 1970s and suggest that the source should revert back to a a spin-up episode.
Description: Open Access
ISSN: 0004-6361
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Copyright: 1994 EDP Sciences
Appears in Collections:Research Papers (A&A)

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