2020ApJ...892..142H

The Type Ia supernova (SN Ia) 2017cfd in IC 0511 (redshift z=0.01209±0.00016) was discovered by the Lick Observatory Supernova Search 1.6 ± 0.7 day after the fitted first-light time (15.2 days before B-band maximum brightness). Photometric and spectroscopic follow-up observations show that SN 2017cfd is a typical, normal SN Ia with a peak luminosity M_B~-19.2±0.2 mag, Δm₁₅(B) = 1.16 mag, and reached a B-band maximum ∼16.8 days after the first light. We estimate there to be moderately strong host-galaxy extinction (A_V = 0.39 ± 0.03 mag) based on MLCS2k2 fitting. The spectrum reveals a Si II λ6355 velocity of ∼11,200 km s^–1 at peak brightness. SN 2017cfd was discovered very young, with multiband data taken starting 2 days after the first light, making it a valuable complement to the currently small sample (fewer than a dozen) of SNe Ia with color data at such early times. We find that its intrinsic early-time (B-V)₀ color evolution belongs to the "blue" population rather than to the distinct "red" population. Using the photometry, we constrain the companion-star radius to be <=2.5 R_☉ with the Kasen model, thus ruling out a red-giant companion.