Context :

Aims : Using XMM Newton data , we investigate the nature of the X-ray emission in the radio relic 1253+275 in the Coma cluster .
We determine the conditions of the cluster gas to check current models of relic formation , and we set constraints on the intracluster magnetic field .

Methods : Both imaging and spectral analysis are performed , and the X-ray emission is compared with the radio emission .

Results : We found that the emission is of thermal origin and is connected to the sub-group around NGC 4839 .
The best-fit gas temperature in the region of the relic and in its vicinity is in the range 2.8 - 4.0 keV , comparable to the temperature of the NGC 4839 sub-group .
We do not detect any high temperature gas , resulting from a possible shock in the region of the Coma relic .
We therefore suggest that the main source of energy for particles radiating in the radio relic is likely to be turbulence .
From the X-ray data , we can also set a flux upper limit of 3.2 \times 10 ^ { -13 } erg cm ^ { -2 } s ^ { -1 } , in the 0.3 - 10 keV energy range , to the non-thermal emission in the relic region .
This leads to a magnetic field B > 1.05 \mu G .

Conclusions :