ROSAT/HRI and ASCA observations of the most luminous X-ray cluster RXJ1347.5-1145

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We report on the X-ray properties of the exceptional X-ray cluster RXJ1347.5-1145 at z=0.451. We confirm that it is with a luminosity Lₓ(bol)=2× 10⁴⁶ erg/s the most luminous X-ray cluster discovered to date. The mass of the cluster within 1.7 Mpc is 9.8%±1.1× 10¹⁴. A comparison of the central X-ray mass and the mass determined from a simple gravitational lens model shows a discrepancy of a factor of 2-3 with the X-ray mass being smaller. The temperature of the cluster is 9.3⁺¹.¹₋₁.₀ keV. We detect a strong FeK line corresponding to a metallicity of 0.33±0.10 in solar units, which is an unexpectedly high value for a distant and hot cluster. There are several hints that the cluster contains an extremely strong cooling flow. With the usual assumptions we derive formally a mass accretion rate of more than 3000 /yr indicating that this may be the largest cooling flow detected so far. To find these extreme properties in this distant cluster which can be taken as an indication of a well relaxed and old system is of high importance for the theory of formation and evolution of clusters.