Millisecond Pulsars, TeV Halos, and Implications For The Galactic Center
  Gamma-Ray Excess
  Observations by HAWC indicate that many young pulsars (including Geminga and
Monogem) are surrounded by spatially extended, multi-TeV emitting regions. It
is not currently known, however, whether TeV emission is also produced by
recycled, millisecond pulsars (MSPs). In this study, we perform a stacked
analysis of 24 MSPs within HAWC's field-of-view, finding between 2.6-3.2 sigma
evidence that these sources are, in fact, surrounded by TeV halos. The
efficiency with which these MSPs produce TeV halos is similar to that exhibited
by young pulsars. This result suggests that several dozen MSPs will ultimately
be detectable by HAWC, including many "invisible" pulsars without radio beams
oriented in our direction. The TeV halos of unresolved MSPs could also dominate
the TeV-scale diffuse emission observed at high galactic latitudes. We also
discuss the possibility that TeV and radio observations could be used to
constrain the population of MSPs that is present in the inner Milky Way,
thereby providing us with a new way to test the hypothesis that MSPs are
responsible for the Galactic Center GeV excess.
