Megan E. DeCesar, Scott M. Ransom, Paul S. Ray
We have searched for millisecond pulsars (MSPs) in two globular clusters
detected by the Fermi Large Area Telescope. These clusters contained no known
MSPs prior to their detections in gamma rays. The discovery of gamma ray
emission from many MSPs and the prevalence of MSPs in globular clusters points
to a population of MSPs as the likely source of the detected GeV emission,
directing our search for new cluster MSPs. We observed NGC 6652 and NGC 6388 at
2 GHz with the Green Bank Ultimate Pulsar Processing Instrument pulsar backend
at the Green Bank Telescope using the coherent dedispersion mode. We have
discovered one MSP in the gamma ray error circle of NGC 6652. This pulsar is
interesting because, while positionally coincident with the GC, it has a much
lower dispersion measure than expected from the NE2001 galactic free electron
density model. It is unclear whether the MSP is a foreground pulsar or a
cluster member, and whether the pulsar, cluster, or both, is responsible for
the gamma ray emission. Timing the MSP will give the pulsar position and a
solid identification of the pulsar as a cluster member if it is within a few
core radii of the cluster center, as well as the opportunity to search for
gamma ray pulsations and determine the origin of the GeV emission.
View original:
http://arxiv.org/abs/1111.0365
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