2008MNRAS.391L.117B

We report the detection of a point source CXO J172337.5-373442 in a Chandra field with a high significance (26.7σ), and the discovery (4σ) of a 48arcsec long X-ray tail emanating from the point source. The X-ray spectra of both the point source and the tail are well described with a single absorbed power law, and the tail is harder (power-law index Γ = 0.14^+0.59_–0.68) than the point source (Γ = 1.78^+0.13_–0.11). From this first detailed spatial, spectral and timing X-ray analysis of CXO J172337.5-373442, and from a plausible optical counterpart found from the archives, we conclude that this source is either a Galactic high-mass X-ray binary with an X-ray jet or a Galactic pulsar with its `pulsar wind nebula' seen as the X-ray tail. Although the currently available data are not enough to distinguish between these two candidates with certainty, a detailed comparison of their known properties with those of CXO J172337.5-373442 favours the latter type. If this identification is correct, then the pulsar should be middle-aged or old, that has escaped from its supernova remnant, and the X-ray tail should originate from the synchrotron emission from either of the following locations: (i) a shocked region or (ii) a jet emanating from the pulsar's magnetosphere.