We discuss the rest-frame ultraviolet emission from the starbursting
galaxy HFLS3 at a redshift of 6.34. The galaxy was discovered in
Herschel/SPIRE data due to its red color in the submillimeter
wavelengths from 250 to 500 μm. Keck/NIRC2 K s -band
adaptive optics imaging data showed two potential near-IR counterparts
near HFLS3. Previously, the northern galaxy was taken to be in the
foreground at z = 2.1, while the southern galaxy was assumed to be
HFLS3's near-IR counterpart. The recently acquired Hubble/WFC3 and
Advanced Camera for Surveys (ACS) imaging data show conclusively that
both optically bright galaxies are in the foreground at z <6. A new
lensing model based on the Hubble imaging data and the millimeter-wave
continuum emission yields a magnification factor of 2.2 ± 0.3,
with a 95% confidence upper limit on the magnification of 3.5. When
corrected for lensing, the instantaneous star formation rate is 1320 M
⊙ yr-1, with the 95% confidence lower limit
around 830 M ⊙ yr-1. The dust and stellar
masses of HFLS3 from the same spectral energy distribution (SED) models
are at the level of 3 × 108 M ⊙ and ~5
× 1010 M ⊙, respectively, with large
systematic uncertainties on assumptions related to the SED model. With
Hubble/WFC3 images, we also find diffuse near-IR emission about 0.5
arcsec (~3 kpc) to the southwest of HFLS3 that remains undetected in the
ACS imaging data. The emission has a photometric redshift consistent
with either z ~ 6 or a dusty galaxy template at z ~ 2.