  We present results from ASCA and ROSAT HRI observations of the powerful radio
galaxy 4C+55.16 at redshift 0.24. Extended soft X-ray emission is imaged by the
ROSAT HRI. The X-ray brightness profile is sharply peaked on the radio galaxy,
characteristic of a strong cooling flow. The X-ray spectrum obtained from ASCA
is consistent with multi-phase intracluster gas. There is evidence for an
absorbed cool component as well as ambient cluster medium in the ASCA spectrum.
A spectral fit, taking a cooling-flow component into account, gives a
temperature of kT=5.4(+1.4/-0.9) keV, metal abundance 0.5(+/-0.1)Zsun, excess
absorption on the cool component, nH=4.9(+3.4/-1.3)E+21 cm-2, and an
absorption-corrected bolometric luminosity of 2.2E+45 erg/s (H0=50km/s/Mpc,
q0=0.5). The mass deposition rate is estimated to be about 1100 Msun/yr from
the spectral analysis, in good agreement with that derived from imaging
analysis of the ROSAT data when corrected for absorption. We tentatively
identify a blue feature, seen about 15 arcsec from the centre of the radio
galaxy in a published optical image, as a gravitationally-lensed arc. The
inferred lensing mass is consistent with the gravitational mass derived from
the X-ray data. The best-estimate of the redshift of the lensed object is
1.5(>0.7). All the observed properties suggest that the environment of 4C+55.16
is similar to known massive cooling flow clusters. This is the first massive
cooling flow to be found around a powerful, radio source with a compact,
GHz-peaked spectrum core.
