Jets in Hydrogen-poor Superluminous Supernovae: Constraints from a Comprehensive Analysis of Radio Observations

The energy source powering the extreme optical luminosity of hydrogen-stripped superluminous supernovae (SLSNe-I) is not known, but recent studies have highlighted the case for a central engine. Radio and/or X-ray observations are best placed to track the fastest ejecta and probe the presence of outflows from a central engine. We compile all the published radio observations of SLSNe-I to date and present three new observations of two new SLSNe-I. None were detected. Through modeling the radio emission, we constrain the subparsec environments and possible outflows in SLSNe-I. In this sample, we rule out on-axis collimated relativistic jets of the kind detected in gamma-ray bursts (GRBs). We constrain off-axis jets with opening angles of 5° (30°) to energies of ${E}_{{\rm{k}}}\lt 4\times {10}^{50}\,\mathrm{erg}$ (${E}_{{\rm{k}}}\lt {10}^{50}\,\mathrm{erg}$) in environments shaped by progenitors with mass-loss rates of $\dot{M}\lt {10}^{-4}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ ($\dot{M}\lt {10}^{-5}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$) for all off-axis angles, assuming fiducial values ${\epsilon }_{e}=0.1$ and ${\epsilon }_{B}=0.01$. The deepest limits rule out emission of the kind seen in faint uncollimated GRBs (with the exception of GRB 060218) and from relativistic SNe. Finally, for the closest SLSN-I, SN 2017egm, we constrain the energy of an uncollimated nonrelativistic outflow like those observed in normal SNe to ${E}_{{\rm{k}}}\lesssim {10}^{48}$ erg.