# The evolution of the 3D shape of the broad-lined type Ic SN 2014ad

## TL;DR

This study uses spectropolarimetry and spectroscopy to analyze the 3D shape and composition of SN 2014ad, revealing complex asymmetries and velocity structures in the ejecta, consistent with jet-driven explosion models.

## Contribution

It provides detailed 3D geometric and compositional insights into a broad-lined Type Ic supernova, linking ejecta asymmetries to jet-driven explosion scenarios.

## Key findings

- Ejecta exhibit aspherical outer layers and spherical interior.
- Oxygen and calcium have distinct spatial distributions and velocities.
- High ejecta velocities are consistent with jet-driven models.

## Abstract

We present optical spectropolarimetry and spectroscopy of the broad-lined Type Ic (Ic-bl) SN 2014ad. Our spectropolarimetric observations cover 7 epochs, from -2 days to 66 days after V-band maximum, and the spectroscopic data were acquired from -2 days to +107 days. The photospheric velocity estimates showed ejecta speeds similar to those of SN 1998bw and other SNe associated with GRBs. The spectropolarimetric data revealed aspherical outer ejecta and a nearly spherical interior. The polarisation associated with O I {\lambda}7774 and the Ca II infrared triplet suggests a clumpy and highly asymmetrical distribution of these two species within the ejecta. Furthermore it was shown that the two line forming regions must have been spatially distinct and oxygen was found to have higher velocities than calcium. Another oxygen line-forming region was also identified much closer to the core of the explosion and distributed in a spherical shell. It is difficult to reconcile the geometry of the deeper ejecta with a jet driven explosion, but the high ejecta velocities of SN 2014ad are typical of those observed in SNe Ic-bl with GRBs, and the behaviour of the oxygen and calcium line-forming regions is consistent with fully jet-driven models. The metallicity of the host galaxy of SN 2014ad was also calculated and compared to that of the hosts of other SNe Ic-bl with and without GRBs, but due to the overlap in the two populations no conclusion could be drawn.