Accurate dust temperature determination in a $z = 7.13$ galaxy
  We report ALMA Band 9 continuum observations of the normal, dusty
star-forming galaxy A1689-zD1 at $z = 7.13$, resulting in a $\sim$4.6$\sigma$
detection at $702$ GHz. For the first time these observations probe the far
infrared (FIR) spectrum shortward of the emission peak of a galaxy in the Epoch
of Reionization (EoR). Together with ancillary data from earlier works, we
derive the dust temperature, $T_{\rm d}$, and mass, $M_{\rm d}$, of A1689-zD1
using both traditional modified blackbody spectral energy density fitting, and
a new method that relies only on the [CII] $158\ \mathrm{\mu m}$ line and
underlying continuum data. The two methods give $T_{\rm d} = (42^{+13}_{-7},
40^{+13}_{-7}$) K, and $M_{\rm d} = (1.7^{+1.3}_{-0.7},
2.0^{+1.8}_{-1.0})\,\times{}\,10^{7} \,M_{\odot}$. Band 9 observations improve
the accuracy of the dust temperature (mass) estimate by $\sim 50$% (6 times).
The derived temperatures confirm the reported increasing $T_{\rm d}$-redshift
trend between $z=0$ and $8$; the dust mass is consistent with a supernova
origin. Although A1689-zD1 is a normal UV-selected galaxy, our results,
implying that $\sim$85% of its star formation rate is obscured, underline the
non-negligible effects of dust in EoR galaxies.
