Closing in on the Fermi Line with a New Observation Strategy

Abstract

Evidence for a spectral line in the inner Galaxy has caused a great deal of excitement over the last year, mainly because of its interpretation as a possible dark matter signal. The observation has raised important questions about statistics and suspicions about systematics, especially in photons from the Earth limb. With enough additional data, we can address these concerns. In this white paper, we summarize the current observational situation and project future sensitivities, finding that the status quo is dangerously close to leaving the issue unresolved until 2015. We advocate a change in survey strategy that more than doubles the data rate in the inner Galaxy, and is relatively non-disruptive to other survey science. This strategy will clearly separate the null hypothesis from the line signal hypothesis and provide ample limb data for systematics checks by the end of 2014. The standard survey mode may not.