2021ApJ...914..125G

In this paper, we investigate the early-time optical-near-infrared (NIR) spectral energy distributions (SEDs) of four Type Ibn supernovae (SNe). We find that the SEDs of SN 2010al, LSQ13ddu, and SN 2015G can be well explained by the single-component blackbody model, while the SEDs of OGLE-2012-SN-006 cannot. We invoke the double-component model assuming that the SEDs were produced by the SN photosphere and the heated dust to fit the optical-NIR SEDs of the four SNe Ibn, finding that the derived temperatures of the dust associated with OGLE-2012-SN-006 favor the scenario that the dust consists of the graphite grains, and the mass and temperature of dust are ∼0.5-2.0 x 10^–3 M_☉ and ∼1200-1300 K, respectively. Moreover, our fits for SN 2010al, LSQ13ddu, and SN 2015G show that the upper limits of the masses of the dust associated with the three SNe Ibn are respectively 1.45 x 10^–5 M_☉, 5.9 x 10^–7 M_☉, and 2.4 x 10^–7 M_☉. A further analysis demonstrates that the inferred radius of the dust shell surrounding OGLE-2012-SN-006 is significantly larger than that of the SN ejecta at early epochs, indicating that the NIR excesses of the SEDs of OGLE-2012-SN-006 were produced by a preexisting dust shell. Our study for the early-time SEDs of four SNe Ibn, together with the previous studies and the fact that some SNe showed evidence of dust formation at the late-time SEDs, indicates that at least ∼1/3 of SNe Ibn show evidence for dust formation.