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A puzzling event during the X-ray emission of the binary system GX 1+4

Nanda Rea·Luigi Stella·Gian Luca Israel·Giorgio Matt·Silvia Zane·Alberto Segreto·Tim Oosterbroek
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Abstract

We report on a long X-ray observation of the slow-rotating binary pulsar GX 1+4. BeppoSAX observed, in the 0.1-200 keV energy range, an event in which the source flux dropped for almost a day, and then recovered. During this event only the high-energy emission was found to be pulsed and the pulsations were shifted in phase of ~0.2 . The spectrum during the event was well fitted by a Compton-reflection model. A broad iron line at ~6.55 keV was present outside of the event, where instead two narrow emission lines at ~6.47 keV and ~7.05 keV were detected. The pulse profile was highly variable as a function of both energy and time. We interpret this low-flux event as an occultation of the direct X-ray emission, due to the increase of a torus-like accretion disk; we then discuss similarities between this source and the recently discovered highly absorbed INTEGRAL sources.

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Nanda Rea, Luigi Stella, Gian Luca Israel, Giorgio Matt, Silvia Zane, Alberto Segreto, Tim Oosterbroek. 2005-04-25. A puzzling event during the X-ray emission of the binary system GX 1+4. https://doi.org/10.1016/j.asr.2005.04.086

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