We present a study of the composite supernova remnant G0.9+0.1 based on observations by XMM-Newton .
The EPIC spectrum shows diffuse X-ray emission from the region corresponding to the radio shell .
The X–ray spectrum of the whole Pulsar Wind Nebula is well fitted by an absorbed power–law model with a photon index \Gamma \sim 1.9 and a 2–10 keV luminosity of about 6.5 \times 10 ^ { 34 } ~ { } { d } _ { \mathrm { 10 } } ^ { 2 } erg s ^ { -1 } ( d _ { 10 } is the distance in units of 10 kpc ) .
However , there is a clear softening of the X-ray spectrum with distance from the core , which is most probably related to the finite lifetime of the synchrotron emitting electrons .
This is fully consistent with the plerionic interpretation of the Pulsar Wind Nebula , in which an embedded pulsar injects energetic electrons into its surrounding region .
At smaller scales , the eastern part of the arc-like feature , which was first revealed by Chandra observations , shows indications of a hard X-ray spectrum with a corresponding small photon index ( \Gamma =1.0 \pm 0.7 ) , while the western part presents a significantly softer spectrum ( \Gamma =3.2 \pm 0.7 ) .
A possible explanation for this feature is fast rotation and subsequent Doppler boosting of electrons : the eastern part of the torus has a velocity component pointing towards the observer , while the western part has a velocity component in the opposite direction pointing away from the observer .