NEAR-INFRARED SPECTROSCOPY OF THE TYPE IIn SN 2010jl: EVIDENCE FOR HIGH VELOCITY EJECTA

The Type IIn supernova SN 2010jl was relatively nearby and luminous, allowing detailed studies of the near-infrared (NIR) emission. We present 1–2.4 μm spectroscopy over the age range of 36–565 days from the earliest detection of the supernova. On day 36, the H lines show an unresolved narrow emission component along with a symmetric broad component that can be modeled as the result of electron scattering by a thermal distribution of electrons. Over the next hundreds of days, the broad components of the H lines shift to the blue by 700 km s −1 , as is also observed in optical lines. The narrow lines do not show a shift, indicating they originate in a different region. He i λ10830 and λ20587 lines both show an asymmetric broad emission component, with a shoulder on the blue side that varies in prominence and velocity from −5500 km s −1 on day 108 to −4000 km s −1 on day 219. This component may be associated with the higher velocity flow indicated by X-ray observations of the supernova. The absence of the feature in the H lines suggests that this is from a He-rich ejecta flow. The He i λ10830 feature has a narrow P Cygni line, with absorption extending to ∼100 km s −1 and strengthening over the first 200 days, and an emission component which weakens with time. At day 403, the continuum emission becomes dominated by a blackbody spectrum with a temperature of ∼1900 K, suggestive of dust emission.