We present new Chandra  X-ray and Giant Meterwave Radio Telescope ( GMRT ) radio observations of the nearby merging galaxy cluster Abell 754 .
Our X-ray data confirm the presence of a shock front by obtaining the first direct measurement of a gas temperature jump across the X-ray brightness edge previously seen in the imaging data .
A 754 is only the fourth galaxy cluster with confirmed merger shock fronts , and it has the weakest shock of those , with a Mach number M = 1.57 ^ { +0.16 } _ { -0.12 } .
In our new GMRT Â observation at 330 MHz , we find that the previously-known centrally located radio halo extends eastward to the position of the shock .
The X-ray shock front also coincides with the position of a radio relic previously observed at 74 MHz .
The radio spectrum of the post-shock region , using our radio data and the earlier results at 74 MHz and 1.4 GHz , is very steep .
We argue that acceleration of electrons at the shock front directly from thermal to ultrarelativistic energies is problematic due to energy arguments , while reacceleration of preexisting relativistic electrons is more plausible .