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ASCA spectroscopy of the luminous infrared galaxy NGC6240: X-ray emission from a starburst and a buried active nucleus

K. Iwasawa·A. Comastri
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Abstract

We present an X-ray spectral 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(3-10keV)=1.4E42 erg/s]. The hard X-ray spectrum indicates that only reflected X-rays of an active galactic nucleus (AGN) buried in a heavy obscuration [N(H)>2E24 cm-2] are visible. This is evidence for an AGN in NGC6240 emitting possibly at a quasar luminosity and suggests its significant contribution to the far-infrared luminosity.

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K. Iwasawa, A. Comastri. 1998-02-26. ASCA spectroscopy of the luminous infrared galaxy NGC6240: X-ray emission from a starburst and a buried active nucleus. https://doi.org/10.1046/j.1365-8711.1998.01588.x

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