Abstract PS1-12sk is a type Ibn supernova (SN) found in a host environment showing no obvious ongoing star formation, which challenges the massive star explosion scenario. We use the ejecta-circumstellar medium (CSM) interaction (CSI) and the CSI plus 56Ni models in the context of double white dwarf (WD) merger to fit the bolometric light curve (LC) of PS1-12sk, since the He emission lines at the photospheric phases indicated the interaction between the SN ejecta and He-rich CSM. We find that the CSI model failed to explain the LC, but the CSI plus 56Ni model can account for the bolometric LC. The derived masses of the two WDs and 56Ni are ∼0.70M⊙, ∼0.40M⊙, and ∼0.09 M⊙, respectively. The facts that the ejecta mass (∼0.984M⊙) is well below the Chandrasekhar limit (∼1.4M⊙) and that the 56Ni mass is comparable to the 56Ni yields of the explosions of some sub-Chandrasekhar explosion models support the scenario that PS1-12sk might be from a sub-Chandrasekhar explosion induced by the merger of two low-mass WDs. The derived innermost radius (∼13.81 × 1012 cm) and the mass of the CSM (∼0.116M⊙) disfavor the possibility that the CSM was formed in the merger phase. We suggest that the flybys before the merger can account for the position and mass of the CSM.
Mi et al. (Sat,) studied this question.