The Herschel Bright Sources (HerBS): Sample definition and SCUBA-2
  observations
  We present the Herschel Bright Sources (HerBS) sample, a sample of bright,
high-redshift Herschel sources detected in the 616.4 square degree H-ATLAS
survey. The HerBS sample contains 209 galaxies, selected with a 500 {\mu}m flux
density greater than 80 mJy and an estimated redshift greater than 2. The
sample consists of a combination of HyLIRGs and lensed ULIRGs during the epoch
of peak cosmic star formation. In this paper, we present SCUBA-2 observations
at 850 ${\mu}$m of 189 galaxies of the HerBS sample, 152 of these sources were
detected. We fit a spectral template to the Herschel-SPIRE and 850 ${\mu}$m
SCUBA-2 flux densities of 22 sources with spectroscopically determined
redshifts, using a two-component modified blackbody spectrum as a template. We
find a cold- and hot-dust temperature of 21.29 K and 45.80 K, a cold-to-hot
dust mass ratio of 26.62 and a $\beta$ of 1.83. The poor quality of the fit
suggests that the sample of galaxies is too diverse to be explained by our
simple model. Comparison of our sample to a galaxy evolution model indicates
that the fraction of lenses is high. Out of the 152 SCUBA-2 detected galaxies,
the model predicts 128.4 $\pm$ 2.1 of those galaxies to be lensed (84.5%). The
SPIRE 500 ${\mu}$m flux suggests that out of all 209 HerBS sources, we expect
158.1 $\pm$ 1.7 lensed sources, giving a total lensing fraction of 76 per cent.
