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

Abstract

We present broad-band 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 because its light curve shows characteristic features - a plateau slope of 2.55 mag (100 d)-1 in the V band and a duration of ~77 d - of a generic Type IIL SN. However, SN 2013hj also shows a high plateau decline rate of 1.5 mag (100 d)-1 in the 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 the radioactive tail of optical light curves. Broad-band polarimetric observations reveal some polarization in SN 2013hj with subtle enhancement as the SN evolves towards the 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 a more asymmetric central region of explosion. Modelling of the bolometric light curve yields a progenitor mass of ~11M⊙ with a radius of ~700 R⊙ for SN 2013hj, while for the SN 2014G model estimated progenitor mass is ~9M⊙ with a radius of ~630 R⊙, both having a typical energy budget of ~2 × 1051 erg.