Polarization Signals of Luminous Supernovae by Jet-driven Bipolar Explosions postprint

Abstract: Superluminous supernovae (SLSNe) and luminous supernovae (LSNe) exhibit extreme luminosities, which require additional energy supply mechanisms such as central engines or circumstellar interaction. In the central-engine scenario, jets inject energy into the polar ejecta, modifying its evolution and shaping the explosion geometry. This study investigates the polarization signatures of jet-driven bipolar explosions in SLSNe/LSNe, where the asymmetric ejecta structure and differential photospheric evolution imprint distinct observational features. We develop a two-component ejecta model, consisting of fast-expanding polar ejecta (powered by jets) and slower equatorial ejecta. We find that polarization exhibits complex temporal evolution, where the ejecta geometry and flux asymmetry between the two regions jointly produce a double-peaked feature. In addition, the line opacity in the polar region further enhances the wavelength dependence of the polarization. Spectropolarimetric observations, particularly during early phases, can constrain the geometry and energy sources of SLSNe/LSNe, advancing our understanding of their explosion mechanisms.