tokens: carbon. The luminosity was obtained by interpolating and fitting the optical ( B , V , i ′) and the NIR ( J – H – K s ) fluxes from Fransson et al. ( 2014 ) at several epochs, in addition to the five epochs (days 87, 254, 465, 621, 844) for which we have Spitzer data. Thereafter, the luminosity, L ( t ), was fitted using a power law of time. The exponents are found to be −0.55 and −4.0 with a switch at day 310, as shown in the figure. We also calculate the UVO luminosity in uniform temporal bins in order to reconstruct the UVO light curve. The evolution of L UVO was thereafter fitted using a power law, t − β , with β = 0.55 before day 310 and β = 4.0 thereafter. The best-fit scenario is presented in Figure 1 (top left). The nature of the luminosity, L ( t ), derived in this study compares well with the findings by Fransson et al. ( 2014 ), Jencson et al. ( 2016 ), and Gall et al. ( 2014 ). The rapid decline in luminosity at later times can be attributed to a change in the density profile at the shock front. A similar drop in luminosity is also reflected in the evolution of the X-rays along the line of sight (Chandra et al. 2015 ). 2.1. Possible Source of the IR Emission In this study, good fits to the IR spectra of SN 2010jl, shown in Figure 1 , were achieved using the contribution from any of the three sources (a blackbody, astronomical silicates, amorphous carbon) as the IR component. Therefore, the best-fit models do not have any strong bias toward any of the three sources being the most likely one. A blackbody fit is appropriate when the dusty shell is optically thick. Additionally, the blackbody radius ( R IR ) represents the minimum possible radius of the dusty shell from where the IR emission originates. The NIR fluxes can be fit well using the absorption coefficients of optically thin astronomical silicates. The upper limit on the 9.7 μ m flux at late times was obtained from the SOFIA observations (Williams Fox 2015 ). It indicates the absence of silicate features. Therefore, the presence of silicates is doubtful, unless the grains are large ( a ∼ 5 μ m) or the dusty shell is optically thick. With only photometric data in the 2.2–4.6 μ m region, many featureless dust species can fit the spectrum. We choose carbon as a likely dust type owing to its relatively large abundance in space compared to other metals. Moreover, the studies dealing with the IR spectra from the preexplosion era also hint at the presence of carbon dust in SN 2010jl (Dwek et al. 2017 ). However, the CSM of SN 2010jl is reported to have a N-rich (Fransson et al. 2014 ) C-depleted environment (N/C =25 ± 15, N/O = 0.85 ± 0.15). In such environments, O-rich dust species are known to be the primary dust components and all of the carbon mostly gets locked up in CO molecules (Sarangi Cherchneff 2013 ). To support this argument, the observation of a N-rich dusty shell around massive stars, such as the Homunculus nebula surrounding Eta Carinae, does not show any
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