LCO network light curves of SN Ia 2018gv

This very asymmetric process should lead to a conspicuous polarimetric signature. By contrast, observations consistently find very low continuum polarization as the signatures from the explosion process largely dominate over the pre-explosion configuration within several days.

Critical information about the interaction of the ejecta with a companion and any circumstellar matter is encoded in the early polarization spectra. In this study, we obtain spectropolarimetry of SN 2018gv with the ESO Very Large Telescope at -13.6 days relative to the B-band maximum light, or ~5 days after the estimated explosion-the earliest spectropolarimetric observations to date of any SN Ia. These early observations still show a low continuum polarization (<=0.2%) and moderate line polarization (0.30+/-0.04% for the prominent SiII{lambda}6355 feature and 0.85+/-0.04% for the high-velocity Ca component).