Detection of Excess Hard X-Ray Emission from the Group of Galaxies HCG 62

We detected an excess of hard X-ray emission at energies above ~4 keV from the group of galaxies HCG 62 using data from the ASCA satellite. The excess emission is spatially extended up to ~10' from the group center and somewhat enhanced toward the north. Its spectrum can be represented by either a power law of photon index 0.8-2.7 or a bremsstrahlung of temperature greater than 6.3 keV. In the 2-10 keV range, the observed hard X-ray flux, (1.0 ± 0.3) × 10 -12 ergs cm -2 s -1 , implies a luminosity of (8.0 ± 2.0) × 10 41 ergs s -1 for a Hubble constant of 50 km s -1 Mpc -1 . The emission is thus too luminous to be attributed to X-ray binaries in the member galaxies. We discuss possible origins of the hard X-ray emission.