Concept of SPARC4:a simultaneous polarimeter and rapid camera in 4 bands

We present a summary of the concept design report of a new astronomical instrument: SPARC4, Simultaneous Polarimeter and Rapid Camera in 4 bands. SPARC4 will provide photometry and polarimetry in four optical broad bands (griz SDSS) simultaneously. This is achieved by the use of dichroic beam splitters. The square eld of view is around 5.6 arcmin on a side. SPARC4 time resolution is sub-second for photometry and somewhat longer for polarimetry. This is provided by the use of fast EMCCDs. The main motivation for building SPARC4 is to explore astrophysical objects which exhibit fast temporal variability in ux and polarization. The instrument will be installed at the 1.6-m telescope of the Observatorio do Pico dos Dias (Brazil).