Intermediate Frequency Gravitational Wave Determination in the 10 micro-Hertz to 20 milli-Hertz Band Using Dense Pulsar Timing Campaigns

Dense, continuous pulsar timing observations over a 24-hr period provide a method for probing intermediate gravitational wave (GW) frequencies of 10 micro-Hertz to 20 milli-Hertz. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array, the European Pulsar Timing Array, and the entire International Pulsar Timing Array all use millisecond pulsar observations to constrain GWs typically at nano-Hz frequencies. In the case of the IPTA's nine-telescope 1713 24-Hour Global Campaign on millisecond pulsar J1713$+$0747 (Dolch et al. 2014), gravitational wave limits in the intermediate frequency regime can be produced. These limits overlap with limits from Cassini Doppler tracking. The negligible change in dispersion measure allows for a white noise model to be used with the timing residuals in order to constrain any contributions from GWs. We show the current status of GW limiting using the 1713 global data. We then discuss the relevant GW sources, and the advantages of using the 1713 global data to limit contributions from such sources. Future campaigns using simultaneous, continuous observations of multiple pulsars will also be discussed.