CosmoCoffee

What do people familiar with the EGRET anomaly think of this paper? Is it indeed likely that it would be just a calibration error, as the authors claim?

At present we really don't know for sure, but up to now it was always stated as unlikely by the instrumentalists. In this paper the view is taken that a particular diffuse emission model is reliable and hence EGRET can be renormalized to it. However no physical basis is given for the instrumental effect, as the authors admit. In fact a recent paper (0706.0503), which does an extensive Monte-Carlo of EGRET, actually finds the excess is underestimated. There are several astrophysical explanations - as referenced in their paper - including, plausibly, cosmic-ray spectra different from local in the Galaxy at large (while their's is based just on the local cosmic-ray spectrum). Another possibility is populations of unresolved sources (astro-ph/0609359). Still, with GLAST to be launched early next year, it is probably best just to wait and see. A more extensive discussion can be found at http://galprop.stanford.edu/forum/viewtopic.php?t=43 .