Discovery of a Multiply-Lensed Submillimeter Galaxy in Early HerMES
  Herschel/SPIRE Data
  We report the discovery of a bright ($f(250\mum) > 400$ mJy), multiply-lensed
submillimeter galaxy \obj\ in {\it
  Herschel}/SPIRE Science Demonstration Phase data from the HerMES project.
Interferometric 880\mum\ Submillimeter Array observations resolve at least four
images with a large separation of $\sim 9\arcsec$. A high-resolution adaptive
optics $K_p$ image with Keck/NIRC2 clearly shows strong lensing arcs. Follow-up
spectroscopy gives a redshift of $z=2.9575$, and the lensing model gives a
total magnification of $\mu \sim 11 \pm 1$. The large image separation allows
us to study the multi-wavelength spectral energy distribution (SED) of the
lensed source unobscured by the central lensing mass. The
far-IR/millimeter-wave SED is well described by a modified blackbody fit with
an unusually warm dust temperature, $88 \pm 3$ K. We derive a lensing-corrected
total IR luminosity of $(1.43 \pm 0.09) \times 10^{13}\, \mathrm{L}_{\odot}$,
implying a star formation rate of $\sim 2500\, \mathrm{M}_{\odot}\,
\mathrm{yr}^{-1}$. However, models primarily developed from brighter galaxies
selected at longer wavelengths are a poor fit to the full optical-to-millimeter
SED. A number of other strongly lensed systems have already been discovered in
early {\it Herschel} data, and many more are expected as additional data are
collected.
