We present an X-ray spectroscopic study of the prototype far-infrared galaxy NGC6240 from ASCA .
The soft X-ray spectrum ( below 2 keV ) shows clear signatures of thermal emission well described with a multi-temperature optically-thin plasma , which probably originates in a powerful starburst .
Strong hard X-ray emission is also detected with ASCA and its spectrum above 3 keV is extremely flat with a prominent iron K line complex , very similar to that seen in the Seyfert 2 galaxy NGC1068 but about an order of magnitude more luminous ( L _ { 3 - 10 keV } \approx 1.4 \times 10 ^ { 42 } erg s ^ { -1 } ) .
The hard X-ray spectrum indicates that only reflected X-rays of an active galactic nucleus ( AGN ) buried in a heavy obscuration ( N _ { H } > 2 \times 10 ^ { 24 } cm ^ { -2 } ) are visible .
This is evidence for an AGN in NGC6240 emitting possibly at a quasar luminosity ( \sim 10 ^ { 45 } erg s ^ { -1 } ) and suggests its significant contribution to the far-infrared luminosity .