A CHANDRA follow-up observation of an X-ray luminous galaxy cluster with a compact appearance , RXCJ1504.1-0248 discovered in our REFLEX Cluster Survey , reveals an object with one of the most prominent cluster cooling cores . A \beta -model fit to the X-ray surface brightness profile gives a core radius of \sim 30 h _ { 70 } ^ { -1 } kpc which is much smaller than the cooling radius with \sim 140 kpc . As a consequence more than 70 % of the high X-ray luminosity of L _ { bol } = 4.3 ~ { } 10 ^ { 45 } h _ { 70 } ^ { -1 } erg s ^ { -1 } of this cluster is radiated inside the cooling radius . A simple modeling of the X-ray morphology of the cluster leads to a formal mass deposition rate within the classical cooling flow model of 1500 - 1900 M _ { \odot } yr ^ { -1 } ( for h _ { 100 } = 0.7 , and 2300 - 3000 M _ { \odot } yr ^ { -1 } for h _ { 100 } = 0.5 ) . The center of the cluster is marked by a giant elliptical galaxy which is also a known radio source . Thus it is very likely that we observe one of the interaction systems where the central cluster AGN is heating the cooling core region in a self-regulated way to prevent a massive cooling of the gas , similar to several such cases studied in detail in more nearby clusters . The interest raised by this system is then due to the high power recycled in RXCJ1504-0248 over cooling time scales which is about one order of magnitude higher than what occurs in the studied , nearby cooling core clusters . The assumption that cooling is exactly balanced by the AGN heating implies a central black hole mass growth rate of the order of 0.5 M _ { \odot } yr ^ { -1 } . This cluster is therefore a prime target for the study of AGN-intracluster medium interaction at very extreme conditions . Further features common to cooling cores found in this cluster are a strong temperature drop towards the center and narrow , low ionization emission lines in the central cluster galaxy . The cluster is also found to be very massive , with a global X-ray temperature of about 10.5 keV and a total mass of about 1.7 ~ { } 10 ^ { 15 } h _ { 70 } ^ { -1 } M _ { \odot } inside 3 h _ { 70 } ^ { -1 } Mpc .