  A search for physics beyond the standard model in final states with at least
one photon, large transverse momentum imbalance, and large total transverse
event activity is presented. Such topologies can be produced in gauge-mediated
supersymmetry models in which pair-produced gluinos or squarks decay to photons
and gravitinos via short-lived neutralinos. The data sample corresponds to an
integrated luminosity of 35.9 inverse femtobarns of proton-proton collisions at
sqrt(s) = 13 TeV recorded by the CMS experiment at the LHC in 2016. No
significant excess of events above the expected standard model background is
observed. The data are interpreted in simplified models of gluino and squark
pair production, in which gluinos or squarks decay via neutralinos to photons.
Gluino masses of up to 1.50-2.00 TeV and squark masses up to 1.30-1.65 TeV are
excluded at 95% confidence level, depending on the neutralino mass and
branching fraction.
