The ⁵⁶Ni Mass, Energy Sources, and Mass-loss History of SN 2014av

Abstract SN 2014av is a type Ibn supernova (SN) characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium (CSM). We use the 56 Ni model, the ejecta-CSM interaction (CSI) model, and the CSI plus 56 Ni model to fit the multiband light curves (LCs) of SN 2014av. For the CSI and CSI plus 56 Ni models, we assume that the CSM is a constant density shell (“shell”) or a steady-state stellar wind (“wind”) with density ∝ r −2 . We find that both the 56 Ni and CSI models fail to fit the multiband LCs of SN 2014av, while the CSI plus 56 Ni model can account for the LCs. In the last scenario, the LCs around the peaks were mainly powered by the CSI, while the flattening of the LCs was mainly powered by the radioactive decay of 56 Ni. For the wind case, the derived mass-loss rate of the progenitor is ≈20.5–205.5 M ⊙ yr −1 , whose lower limit is significantly larger than the upper limit of normal stellar winds, and comparable the upper limit of hyper-winds. Hence, we suggest that the wind case is disfavored. For the shell case, the best-fitting values of the ejecta, 56 Ni, and the CSM are 2.29 M ⊙ , 0.09 M ⊙ , and 5.00 M ⊙ , respectively. Provided the velocity of the CSM shell is 100–1000 km s −1 , we infer that the shell might be expelled ≈0.49–5.20 yr before the SN exploded.