A Day in the Life of Millisecond Pulsar J1713+0747: Limits on Timing Precision Over 24 Hours and Implications for Gravitational Wave Detection

A 24-hour global observation of millisecond radio pulsar J1713+0747 was undertaken by the International Pulsar Timing Array (IPTA) collaboration as an effort to better quantify sources of noise in this object, which is regularly timed for the purpose of detecting gravitational waves (GWs). Given an 8-year timing RMS of 30ns, it is regarded as one of the best precision clocks in the PTA. However, sources of timing noise visible on timescales longer than the usual 20-30min biweekly observation may nonetheless be present. Data from the campaign were taken contiguously with the Parkes, Arecibo, Green Bank, GMRT, LOFAR, Effelsberg, WSRT, Lovell, and Nancay radio telescopes. The combined pulse times-of-arrival provide an estimate of the absolute noise floor, in other words, what unaccounted sources of timing noise impede an otherwise simple sqrt(N) improvement in timing precision, where N is the number of pulses in a single observing session. We present first results of specific phenomena probed on the unusual timescale of tens of hours, in particular interstellar scattering (ISS), and discuss the degree to which ISS affects precision timing. Finally, we examine single pulse information during selected portions of the observation and determine the degree to which the pulse jitter of J1713+0747 varies throughout the course of the day-long dataset.