SN 2012fr: ultraviolet, optical, and near-infrared light curves of a type Ia supernova observed within a day of explosion

Author(s): Contreras, C; Phillips, MM; Burns, CR; Piro, AL; Shappee, BJ; Stritzinger, MD; Baltay, C; Brown, PJ; Conseil, E; Klotz, A; Nugent, PE; Turpin, D; Parker, S; Rabinowitz, D; Hsiao, EY; Morrell, N; Campillay, A; Castellon, S; Corco, C; Gonzalez, C; Krisciunas, K; Seron, J; Tucker, BE; Walker, ES; Baron, E; Cain, C; Childress, MJ; Folatelli, G; Freedman, WL; Hamuy, M; Hoeflich, P; Persson, SE; Scalzo, R; Schmidt, B; Suntzeff, NB | Abstract: © 2018. The American Astronomical Society. All rights reserved.. We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ∼2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred l22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ g 1800) luminosity was 16.5 ±0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ±0.15 M o of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ∼12,000 that began ∼5 days before . We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.