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H. Steinle (MPE)
During five ROSAT HRI observations in July 1995, a bright X-ray source (designated 1RXH~J132519.8-430312) was detected 2.5 arcmin south-west of the nucleus of NGC~5128 (Centaurus~A) at the outer regions of the elliptical galaxy.
At that time it was the brightest point source in the ROSAT HRI field-of-view. All other ROSAT observations made before and after this observations show no trace of the source suggesting that this is a highly variable object. Chandra observations of Cen~A made in September 1999 show a source at the ROSAT position, which may be the quiescent counterpart of the transient. It is very probable that the transient is located in NGC~5128.
Given the existence of a transient source that close to the direction of NGC~5128, all observations (at least in soft X-rays) of Cen~A, with instruments of low spatial resolution, should take the variability of this object into account.
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