Detection of Excess Hard X-ray Emission from the Group of Galaxies HCG62

Abstract

From the group of galaxies HCG62, we detected an excess hard X-ray emission in energies above $\sim 4$ keV with \A SCA. The excess emission is spatially extended up to $\sim 10^{\prime }$ from the group center, and somewhat enhanced toward north. Its spectrum can be represented by either a power-law of photon index 0.8-2.7, or a Bremsstrahlung of temperature $>6.3$ keV. In the 2-10 keV range, the observed hard X-ray flux, $(1.0\pm 0.3)\times 10^{-12}$ erg cm${}^{-2}$ s${}^{-1}$, implies a luminosity of $(8.0\pm 2.0)\times 10^{41}$ erg 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 memb er galaxies. We discuss possible origin of the hard X-ray emission.

6 pages, 3 Postscript figures, uses emulateapj.sty. Accepted for publication in the Astrophysical Journal Letters

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