Discovery of a non-thermal X-ray filament in the Galactic Centre

Masaaki Sakano1, Robert S. Warwick1, Anne Decourchelle2

1 Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
2 Service d'Astrophysique, CEA Saclay, L'Orme des merisiers, bat. 709, F-91191 Gif-sur-Yvette, France

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We report the discovery of an X-ray filament, XMM J174540-2904.5 in the Galactic Centre region, which is located 4' south of Sgr A*. The X-ray images of XMM J174540-2904.5, taken with Chandra and XMM-Newton, are found to be clearly extended and to coincide well with a radio non-thermal structure, although the X-ray emitting region is limited in a part of the radio structure. Its X-ray spectrum shows a heavy absorption, probably because this filament is located at the dust-emission peak of the ``20 km s-1'' cloud. The spectrum is proved not to be thermal, but is well approximated with a power-law of the (energy) index of 1. From the radio and X-ray spectra, we concluded both the emissions to be originated in the same synchrotron process. XMM J174540-2904.5 can be a synchrotron filament in the Galactic Centre region, in which some mechanism for the particle acceleration may be working, although the possibility of the background AGN is not excluded.