  Superluminous supernovae (SLSNe) are a rare class of stellar explosions with
luminosities ~10-100 times greater than ordinary core-collapse supernovae. One
popular model to explain the enhanced optical output of hydrogen-poor (Type I)
SLSNe invokes energy injection from a rapidly spinning magnetar. A prediction
in this case is that high-energy gamma rays, generated in the wind nebula of
the magnetar, could escape through the expanding supernova ejecta at late times
(months or more after optical peak). This paper presents a search for gamma-ray
emission in the broad energy band from 100 MeV to 30 TeV from two Type I SLSNe,
SN2015bn, and SN2017egm, using observations from Fermi-LAT and VERITAS.
Although no gamma-ray emission was detected from either source, the derived
upper limits approach the putative magnetar's spin-down luminosity. Prospects
are explored for detecting very-high-energy (VHE; 100 GeV - 100 TeV) emission
from SLSNe-I with existing and planned facilities such as VERITAS and CTA.
