We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II λ6355 line that can be cleanly decoupled from the lower velocity "photospheric" component. This Si II λ6355 HVF fades by phase -5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of 12,000 km s-1 until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v 12,000 km s-1 with narrow line width and long velocity plateau, as well as an HVF beginning at v 31,000 km s-1 two weeks before maximum. SN 2012fr resides on the border between the "shallow silicon" and "core-normal" subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the "low velocity gradient" group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia. © 2013. The American Astronomical Society. All rights reserved..
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Childress, M., Scalzo, R., Sim, S., Tucker, B., Yuan, F., Schmidt, B., Cenko, S., Silverman, J., Contreras, C., Hsiao, E., Phillips, M., Morrell, N., Jha, S., McCully, C., Filippenko, A., Anderson, J., Benetti, S., Bufano, F., De Jaeger, T., Forster, F., Gal-Yam, A., Le Guillou, L., Maguire, K., Maund, J., Mazzali, P., Pignata, G., Smartt, S., Spyromilio, J., Sullivan, M., Taddia, F., Valenti, S., Bayliss, D., & Bessell, M. (2013). Spectroscopic observations of sn 2012fr: A luminous, normal type ia supernova with early high-velocity features and a late velocity plateau. Astrophysical Journal, 770 (1) https://doi.org/10.1088/0004-637X/770/1/29