Implications of a 130 GeV Gamma-Ray Line for Dark Matter
  Recent reports of a gamma-ray line feature at ~130 GeV in data from the Fermi
Gamma-Ray Space Telescope have generated a great deal of interest in models in
which dark matter particles annihilate with a sizable cross section to final
states including photons. In this article, we take a model-independent
approach, and discuss a number of possibilities for dark matter candidates
which could potentially generate such a feature. While we identify several
scenarios which could lead to such a gamma-ray line, these models are each
fairly constrained. In particular, viable models require large couplings
(g>1-3), and additional charged particles with masses in the range of
approximately ~130-200 GeV. Furthermore, lower energy gamma-ray constraints
from the Galactic Center force us to consider scenarios in which the dark
matter annihilates in the early universe through velocity-suppressed processes,
or to final states which yield relatively few gamma-rays (such as electrons,
muons or neutrinos). An exception to these conclusions can be found in models
in which the dark matter annihilates to heavy intermediate states which decay
to photons to generate a line-like gamma-ray spectrum.
