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

We report on a long X-ray observation of the 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 similar to 0.2. The spectrum during the event was well fitted by a Compton-reflection model. A broad iron line at similar to 6.55 keV was present outside of the event, where instead two narrow emission lines at similar to 6.47 and similar to 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. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.