  Results are presented from a semicoherent search for continuous gravitational
waves from a nearby neutron star candidate, Fomalhaut b, using data collected
in the second observing run of Advanced LIGO. The search is based on a hidden
Markov model scheme, capable of tracking signal frequency evolution from the
star's secular spin down and stochastic timing noise simultaneously. The scheme
is combined with a frequency domain matched filter ($\mathcal{F}$-statistic),
calculated coherently over five-day time stretches. The frequency band 100-1000
Hz is searched. After passing the above-threshold candidates through a
hierarchy of vetoes, one candidate slightly above the 1% false alarm
probability threshold remains for further scrutiny. No strong evidence of
continuous waves is found. We present the strain upper limits in the full
frequency band searched at 90% confidence level.

General Relativity and Quantum Cosmology;Instrumentation and Methods for Astrophysics