Photometric and polarimetric observations of fast declining Type II supernovae 2013hj and 2014G

TL;DR

This study presents detailed photometric and polarimetric observations of two Type II supernovae, confirming their classification and analyzing their polarization and progenitor properties to understand explosion asymmetries.

Contribution

It provides the first comprehensive broadband photometric and polarimetric analysis of SNe 2013hj and 2014G, including progenitor modeling and polarization behavior during evolution.

Findings

SN 2014G is a Type IIL supernova with a characteristic light curve slope.

SN 2013hj shows high plateau decline rate, similar to SNe IIL.

Polarization remains constant in angle, indicating asymmetric core revealing during evolution.

Abstract

We present broadband photometric and polarimetric observations of two type II supernovae (SNe) 2013hj and 2014G. SN 2014G is a spectroscopically classified type IIL event, which we also confirm photometrically as its light curve show characteristic features (plateau slope of 2.55 mag (100 d)$ ^{-1} $ in V-band and duration of $ \sim77 $d) of a generic IIL SN. On the other hand SN 2013hj also shows high plateau decline rate of $ 1.5 $ mag (100 d)$ ^{-1} $ in V-band, similar to SNe IIL, but marginally lower than SNe IIL template light curves. Our high cadence photometric observations of SNe 2013hj and 2014G enables us to cover all characteristic phases up to radioactive tail of optical light curves. Broadband polarimetric observations reveal some polarization in SN 2013hj with subtle enhancement as SN evolves towards plateau end, however the polarization angle remains constant throughout the evolution. This characteristic is consistent with the idea that the evolving SN with recombining hydrogen envelope is slowly revealing more asymmetric central region of explosion. Modelling of bolometric light curve yields a progenitor mass of $ \sim11 $M$_{\odot}$ with a radius of $ \sim700 $R$_{\odot}$ for SN 2013hj, while for SN 2014G model estimated progenitor mass is $ \sim9 $M$_{\odot}$ with a radius of $ \sim630 $R$_{\odot}$, both having a typical energy budget of $ \sim2\times10^{51} $ erg.