  We search for continuous gravitational waves (CGWs) produced by individual
super-massive black-hole binaries (SMBHBs) in circular orbits using
high-cadence timing observations of PSR J1713$+$0747. We observe this
millisecond pulsar using the telescopes in the European Pulsar Timing Array
(EPTA) with an average cadence of approximately 1.6 days over the period
between April 2011 and July 2015, including an approximately daily average
between February 2013 and April 2014. The high-cadence observations are used to
improve the pulsar timing sensitivity across the GW frequency range of
$0.008-5$ $\mu$Hz. We use two algorithms in the analysis, including a spectral
fitting method and a Bayesian approach. For an independent comparison, we also
use a previously published Bayesian algorithm. We find that the Bayesian
approaches provide optimal results and the timing observations of the pulsar
place a 95 per cent upper limit on the sky-averaged strain amplitude of CGWs to
be $\lesssim3.5\times10^{-13}$ at a reference frequency of 1 $\mu$Hz. We also
find a 95 per cent upper limit on the sky-averaged strain amplitude of
low-frequency CGWs to be $\lesssim1.4\times10^{-14}$ at a reference frequency
of 20~nHz.
