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 ( 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 d 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 ± 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 gamma-ray burst/X-ray flash associated SNe (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 II features. The expansion velocity of the ejecta near maximum light reached ∼ 16 000 km s − 1 and settled to ∼ 8000 km s − 1 , ∼ 1 month post-maximum. Analytical modelling of the quasi-bolometric light curve of ASASSN-16fp suggests that ∼ 0.1 M

56 Ni mass was synthesized in the explosion, with a kinetic energy of 6.9 + 1 . 5 − 1 . 3 × 10 51 erg and total ejected mass of ∼ 4.5 ± 0.3 M

.