We report the discovery of a bright ( f \left ( 250 \mu \mathrm { m } \right ) > 400 mJy ) , multiply-lensed submillimeter galaxy HERMES J105751.1+573027 in Herschel /SPIRE Science Demonstration Phase data from the HerMES project ( 23 ) .
Interferometric 880 \mu \mathrm { m } 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 \left ( 1.43 \pm 0.09 \right ) \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 Herschel data , and many more are expected as additional data are collected .