Abstract: | Results are presented from a semi-coherent search for continuous
gravitational waves from the brightest low-mass X-ray binary, Scorpius X-1,
using data collected during the first Advanced LIGO observing run (O1). The
search combines a frequency domain matched filter (Bessel-weighted
$mathcal{F}$-statistic) with a hidden Markov model to track wandering of the
neutron star spin frequency. No evidence of gravitational waves is found in the
frequency range 60-650 Hz. Frequentist 95% confidence strain upper limits,
$h_0^{95\%} = 4.0 imes10^{-25}$, $8.3 imes10^{-25}$, and $3.0 imes10^{-25}$
for electromagnetically restricted source orientation, unknown polarization,
and circular polarization, respectively, are reported at 106 Hz. They are $leq
10$ times higher than the theoretical torque-balance limit at 106 Hz. |