impossible but unusually large. It would imply a young 8 Myr old starburst with a mass of 2$\times$10$^{9}$ M$_{\sun}$ and a true star-formation rate, as derived from extinction correction of the ultraviolet flux, of $\sim$100 M$_{\sun}$ yr$^{-1}$, all of which is dust obscured. The fits to the mid-infrared photometry at $z=0.6$ imply a much lower dust-obscured star-formation rate of $\sim$5 M$_{\sun}$ yr$^{-1}$. Although it is possible for optically thick star-formation, such as that found in local ULIRGs, to result in the mid- and far-infrared luminosity of galaxies exceeding their extinction corrected ultraviolet luminosity, the converse is rarely true. This weakens the possibility of a $z=0.6$ starburst.

If the source is a $z=0.6$ obscured AGN like Mrk231, then the contribution of the hot dust around the AGN to the near-infrared photometry needs to be subtracted before fitting. For the Mrk231 template, we find this to be 0.8, 1.2, 1.4, 2.6, 3.5, 5.6 and 10.5$\mu$Jy at 1.2, 1.6, 2.2, 3.6, 4.5, 5.8 and 8.0$\mu$m respectively. The photometry at 1.1 and 1.6[$\mu$m]{} of the source is a factor of $3-10$ below the expected values again indicating that a Mrk231 type source, while consistent with the mid-infrared photometry, cannot fit the entire SED.

Thus, 