The Eclipsing Binary Pulsar J1638-4725

PSR J16384725 is in a highly eccentric binary system with a 5yr orbital periodabout a massive companion. The pulsar is undetectable in the radio for roughly 1yr around periastron, most likely due to absorption and scattering by the densestellar environment. During this radioquiet phase, Xrays produced by propellerregime accretion of matter onto the neutron star magnetosphere are likely to bedetectable. If such emission is detected, this binary will be the first systemin which an accretion phase alternates with a radio pulsar phase. Observationsof the Xray emission close to periastron will provide an important diagnosticof the properties of the companion star and its wind. Such an opportunity willnot be available for another 5 years. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]