  We have combined optical and NIR photometry from Pan-STARRS 1 and UKIDSS to
search the young (5-10 Myr) star-forming region of Upper Scorpius for wide
(~400-4000 AU) substellar companions down to ~5 Mjup. Our search is ~4mag
deeper than previous work based on 2MASS. We identified several candidates
around known stellar members using a combination of color selection and
spectral energy distribution fitting. Our followup spectroscopy has identified
two new companions as well as confirmed two companions previously identified
from photometry, with spectral types of M7.5-M9 and masses of ~15-60 Mjup,
indicating a frequency for such wide substellar companions of ~0.6+/-0.3%. Both
USco1610-1913B and USco1612-1800B are more luminous than expected for their
spectral type compared with known members of Upper Sco. HIP77900B has an
extreme mass ratio (M2/M1~0.005) and an extreme separation of 3200 AU.
USco1602-2401B also has a very large separation of 1000 AU. We have also
confirmed a low-mass stellar companion, USco1610-2502B (730AU, M5.5). Our
substellar companions appear both non-coeval with their primary stars according
to evolutionary models and, as a group, are systematically more luminous than
the Upper Sco cluster sequence. One possible reason for these luminosity
discrepancies could be different formation processes or accretion histories for
these objects.
