Emergence of the 1 μm P Cygni feature in time. The selected spectra are from 0.48 days (LDSS, Shappee et al. 2017), 0.92 days (ANU, Andreoni et al. 2017), 1.17 days (SALT, Buckley et al. 2018), 1.43 days (X-shooter, Pian et al. 2017), 1.47 days (SOAR, Nicholl et al. 2017 and Gemini-South, Chornock et al. 2017), and 2.42 days (X-shooter, Smartt et al. 2017). The spectra before 1 day do not deviate strongly from the blackbody continuum. However, between 0.92 and 1.17 days, strong absorption appears, while the bulk emission begins to emerge with a delay of around 10 hours. This is the predicted emergence time-frame for both emission and absorption (and the early spectral shape) for a feature produced by LTE Sr II due to a recombination wave passing through the ejecta (Sneppen et al. 2023a), and it is inconsistent with a He Iλ1083.0 nm interpretation (Sneppen et al. 2024).