We present spectral measurements made in the soft ( 20–100 keV ) gamma-ray band of the region containing the composite supernova remnant G11.2-0.3 and its associated pulsar PSR J1811 - 1925 .
Analysis of INTEGRAL/IBIS data allows characterisation of the system above 10 keV .
The IBIS spectrum is best fitted by a power law having photon index \Gamma = 1.8 _ { -0.3 } ^ { +0.4 } and a 20–100 keV flux of 1.5 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } .
Analysis of archival Chandra data over different energy bands rules out the supernova shell as the site of the soft gamma-ray emission while broad band ( 1–200 keV ) spectral analysis strongly indicates that the INTEGRAL/IBIS photons originate in the central zone of the system which contains both the pulsar and its nebula .
The composite X-ray and soft gamma-ray spectrum indicates that the pulsar provides around half of the emission seen in the soft gamma-ray domain ; its spectrum is hard with no sign of a cut off up to at least 80 keV .
The other half of the emission above 10 keV comes from the PWN ; with a \Gamma =1.7 its spectrum is softer than that of the pulsar .
From the IBIS/ISGRI mosaics we are able to derive 2 \sigma upper limits for the 20–100 keV flux from the location of the nearby TeV source HESS J1809 - 193 to be 4.8 \times 10 ^ { -12 } erg cm ^ { -2 } s ^ { -1 } .
We have also examined the likelihood of an association between PSR J1811 - 1925 and HESS J1809 - 193 .
Although PSR J1811 - 1925 is the most energetic pulsar in the region , the only one detected above 10 keV and thus a possible source of energy to fuel the TeV fluxes , there is no morphological evidence to support this pairing , making it an unlikely counterpart .