  So called superluminous supernovae have been recently discovered in the local
Universe. It appears possible that some of them originate from stellar
explosions induced by the pair instability mechanism. Recent stellar evolution
models also predict pair instability supernovae (PISNe) from very massive stars
at fairly high metallicities (i.e. Z~0.004). We provide supernova (SN) models
and synthetic light curves for two progenitor models, a 150 Msun red-supergiant
and a 250 Msun yellow-supergiant at a metallicity of Z=0.001, for which the
evolution from the main sequence to collapse, and the initiation of the PISN
itself, has been previously computed in a realistic and self-consistent way. We
are using the radiation hydrodynamics code STELLA to describe the SN evolution
of both models over a time frame of about 500 days. We describe the
shock-breakout phases of both SNe which are characterized by a higher
luminosity, a longer duration and a lower effective temperature than those of
ordinary SNeIIP. We derive the bolometric as well as the U, B, V, R and I light
curves of our PISN models, which show a long-lasting plateau phase with maxima
at Mbol=-19.3 mag and -21.3 mag for our lower and higher mass model,
respectively. We also describe the photospheric composition and velocity as
function of time. We conclude that the light curve of the explosion of our
initially 150 Msun star resembles those of relatively bright SNeIIP, whereas
its photospheric velocity at early times is smaller. Its 56Ni mass of 0.04 Msun
also falls well into the range found in ordinary core collapse SNe. The light
curve and photospheric velocity of our 250 Msun models has a striking
resemblance with that of the superluminous SN2007bi, strengthening its
interpretation as PISN. We conclude that PISNe may occur more frequently in the
local universe than previously assumed.
