SIMBAD references

We present X-ray results on the ultraluminous infrared galaxy Arp 220 obtained with BeppoSAX. X-ray emission up to 10keV is detected. No significant signal is detected with the PDS detector in the higher energy band. The 2-10keV emission has a flat spectrum (Γ∼1.7), similar to M82, and a luminosity of ∼1x10⁴¹erg.s^–1. A population of X-ray binaries may be a major source of this X-ray emission. The upper limit of an iron K line equivalent width at 6.4keV is ≃600eV. This observation imposes the tightest constraint so far on an active nucleus if present in Arp 220. We find that a column density of X-ray absorption must exceed 10²⁵cm^–2 for an obscured active nucleus to be significant in the energetics, and the covering factor of the absorption should be almost unity. The underluminous soft X-ray starburst emission may need a good explanation, if the bolometric luminosity is primarily powered by a starburst.