  IGR J17062-6143 is an ultra-compact X-ray binary (UCXB) with an orbital
period of 37.96 min. It harbours a millisecond X-ray pulsar that is spinning at
163 Hz and and has continuously been accreting from its companion star since
2006. Determining the composition of the accreted matter in UCXBs is of high
interest for studies of binary evolution and thermonuclear burning on the
surface of neutron stars. Here, we present a multi-wavelength study of IGR
J17062-6143 aimed to determine the detailed properties of its accretion disc
and companion star. The multi-epoch photometric UV to near-infrared spectral
energy distribution (SED) is consistent with an accretion disc
$F_{\nu}\propto\nu^{1/3}$. The SED modelling of the accretion disc allowed us
to estimate an outer disc radius of $R_{out}=2.2^{+0.9}_{-0.4} \times 10^{10}$
cm and a mass-transfer rate of $\dot{m}=1.8^{+1.8}_{-0.5}\times10^{-10}$
M$_{\odot}$ yr$^{-1}$. Comparing this with the estimated mass-accretion rate
inferred from its X-ray emission suggests that $\gtrsim$90% of the transferred
mass is lost from the system. Moreover, our SED modelling shows that the
thermal emission component seen in the X-ray spectrum is highly unlikely from
the accretion disc and must therefore represent emission from the surface of
the neutron star. Our low-resolution optical spectrum revealed a blue continuum
and no emission lines, i.e. lacking H and He features. Based on the current
data we cannot conclusively identify the nature of the companion star, but we
make recommendations for future study that can distinguish between the
different possible evolution histories of this X-ray binary. Finally, we
demonstrate how multiwavelength observations can be effectively used to find
more UCXBs among the LMXBs.
