The discovery of a new non-thermal X-ray filament near the Galactic Centre

We report the discovery by XMM-Newton and Chandra of a hard extended X-ray source (XMM J174540-2904.5) associated with a compact non-thermal radio filament (the Sgr A-E 'wisp'= 1LC 359.888-0.086 = G359.88-0.07), which is located within similar to4 arcmin of the Galactic Centre. The source position is also coincident with the peak of the molecular cloud M-0.13-0.08 (the '20 km s(-1)' cloud). The X-ray spectrum is non-thermal with an energy index of 1.0(-0.9) (+1.1) and a column density of 38(-11) (+7) x 10(22) H cm(-2). The observed 2-10 keV flux of 4 x 10(-13) erg s(-1)cm(-2) converts to an unabsorbed X-ray luminosity of 1 x 10(34) erg s(-1) assuming a distance of 8.0 kpc. The high column density strongly suggests that this source is located in or behind the Galactic Centre region. Taking account of the broad-band spectrum, as well as the source morphology and the positional coincidence with a molecular cloud, we conclude that both the radio and X-ray emission are the result of synchrotron radiation. This is the first time that a filamentary structure in the Galactic Centre region has been shown, unequivocally, to have a non-thermal X-ray spectrum.