Post maximum light and late time optical imaging polarimetry of type I superluminous supernova 2020znr

TL;DR

This study conducted optical polarimetry on superluminous supernova 2020znr at multiple phases, finding no significant polarization and suggesting that higher ejecta mass may obscure inner ejecta geometry, highlighting the need for expanded polarimetric data.

Contribution

It provides the first late-time polarimetric measurements of SN 2020znr and compares its properties with other SLSNe, emphasizing the importance of early and late polarimetry for understanding supernova geometry.

Findings

All measurements are consistent with null polarization.

SN 2020znr has similar magnetar and ejecta parameters to other SLSNe.

Higher ejecta mass may hinder access to inner ejecta geometry.

Abstract

Optical imaging polarimetry was conducted on the hydrogen poor superluminous supernova 2020znr during 3 phases after maximum light (approximately +34 days, +288 days and +289 days). After instrumental and interstellar polarization correction, all measurements are consistent with null-polarization detection. Modelling the light curve with a magnetar spin-down model shows that SN 2020znr has similar magnetar and ejecta parameters to other SLSNe. A comparison of the best-fit values discussed in the literature on SN 2017egm and SN 2015bn, two hydrogen poor SLSNe showing an increase of polarization after maximum light, suggests that SN 2020znr has higher mass ejecta that may prevent access to the geometry of the inner ejecta with optical polarimetry. The combined information provided by spectroscopy and light curve analysis of type I SLSNe may be an interesting avenue to categorize the polarization properties of this class of transients. This approach would require to expand the sample of SLSNe polarimetry data currently available with early and late time epochs new measurements.