ASASSN-16fp (SN 2016coi): A transitional supernova between Type Ic and broad-lined Ic

Abstract

We present results based on a well sampled optical ($UBVRI$) and ultraviolet ({\it Swift}/UVOT) imaging, and low-resolution optical spectroscopic follow-up observations of the nearby Type Ic supernova (SN) ASASSN-16fp (SN 2016coi). The SN was monitored during the photospheric phase ($-10$ to $+$33 days with respect to the $B$-band maximum light). The rise to maximum light and early post-maximum decline of the light curves are slow. The peak absolute magnitude ($M_V$ = $-17.7\pm 0.2$ mag) of ASASSN-16fp is comparable with broad-lined Ic SN 2002ap, SN 2012ap and transitional Ic SN 2004aw but considerably fainter than the GRB/XRF associated supernovae (e.g. SN 1998bw, 2006aj). Similar to the light curve, the spectral evolution is also slow. ASASSN-16fp shows distinct photospheric phase spectral lines along with the C\,{\sc ii} features. The expansion velocity of the ejecta near maximum light reached $\sim$16000 km s${}^{-1}$ and settled to $\sim$8000 km s${}^{-1}$, $\sim$1 month post-maximum. Analytical modelling of the quasi-bolometric light curve of ASASSN-16fp suggests that $\sim$0.1 M${}_{\odot }$ ${}^{56}$Ni mass was synthesized in the explosion, with a kinetic energy of 6.9${}_{-1.3}^{+1.5}$ $\times$ 10${}^{51}$ erg and total ejected mass of $\sim$4.5\,$\pm$\,0.3 M${}_{\odot }$.

13 pages, 14 figures, accepted for publication in MNRAS