Upper Limits on Gamma-Ray Leakage from Superluminous Supernovae with VERITAS and Fermi-LAT

The powering mechanism for the bright luminosity in Superluminous supernovae (SLSNe) is a still-unsettled question. The light curves of conventional core-collapse supernovae are primarily derived from the decay of Ni, while the presence of hydrogen in type II SLSNe spectra indicates interactions between circumstellar medium and the expanding ejecta. Alternatively, hydrogen-poor type I SLSNe may be powered by a central engine such as a highly magnetized pulsar, creating gamma rays that thermalize in the outflowing ejecta and power the bright optical emission. These gamma rays may escape the ejecta as the opacity drops, and become visible after several hundred days. In this talk, we report the search for gamma rays with VERITAS from two bright and nearby type I SLSNe, SN2015bn and SN2017egm, 133 and 670 days after explosion, respectively. We found no detections and report upper limits. We also report upper limits with Fermi-LAT for six-month bins after the explosion. We conclude by reporting the viability for future observation strategies by other ground-based gamma-ray telescopes. This work is presented on behalf of VERITAS Collaboration.