  Dense, continuous pulsar timing observations over a 24-hr period provide a
method for probing intermediate gravitational wave (GW) frequencies from 10
microhertz to 20 millihertz. The European Pulsar Timing Array (EPTA), the North
American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes
Pulsar Timing Array (PPTA), and the combined International Pulsar Timing Array
(IPTA) all use millisecond pulsar observations to detect or constrain GWs
typically at nanohertz frequencies. In the case of the IPTA's nine-telescope
24-Hour Global Campaign on millisecond pulsar J1713+0747, GW limits in the
intermediate frequency regime can be produced. The negligible change in
dispersion measure during the observation minimizes red noise in the timing
residuals, constraining any contributions from GWs due to individual sources.
At 10$^{-5}$Hz, the 95% upper limit on strain is 10$^{-11}$ for GW sources in
the pulsar's direction.
