  Gamma ray emission from dark matter subhalos in the Milky Way has long been
sought as a sign of dark matter particle annihilation. So far, searches for
gamma-ray continuum from subhalos have been unsuccessful, and line searches are
difficult without prior knowledge of the line energies. Guided by recent claims
of line emission at 111 GeV and 129 GeV in the Galactic center, we examine the
co-added gamma-ray spectrum of unassociated point sources in the Second
Fermi-LAT catalog (2FGL) using 3.9 years of LAT data. Using the SOURCE event
class, we find evidence for lines at 111 GeV and 129 GeV with a local
significance of 3.3 sigma based on a conservative estimate of the background at
E>135 GeV. Other 2FGL sources analyzed in the same way do not show line
emission at 111 GeV and 129 GeV. The line-emitting sources are mostly within 30
degrees of the Galactic plane, although this anisotropy may be a selection
effect. If the double-line emission from these objects is confirmed with future
data, it will provide compelling support for the hypothesis that the Galactic
center line signal is indeed from dark matter annihilation.
