dip and a pileup of the cascaded neutrinos right below the dip. For Model A, the spectrum cutoff is steepened and a small pileup is produced. These features are potentially large enough to be observed, and may even explain the gap seen in the IceCube spectrum at moderate energies.

The lowest energy events currently observed by IceCube are $\simeq 0.03\,{\rm PeV}$, which means small mediator masses like those for Model D are difficult to observe through an obvious dip. Of course, even if the resonance energy is below the detector energy threshold, its effects can be observed if the coupling is large enough. At the other extreme, the largest mediator masses that can be observed through an obvious dip depend on the highest observed neutrino energies. Similarly, even larger mediator masses can be probed if the coupling is large enough.

In Fig. \[fig:astro2\], we show the effects of extending the spectrum to higher energies with and without $\nu$SI. Without $\nu$SI, these spectra extend to energies well above what IceCube has observed, and therefore are unrealistic. However, it is possible that the emitted spectrum does extend to high energies, but $\nu$SI lead to the observed cutoff near 1 PeV. We use 