SN 2017cfd: A Normal Type Ia Supernova Discovered Very Young

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 MB >> -19.2. 0.2 mag,.m15(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 (AV.=.0.39.+/-.0.03 mag) based on MLCS2k2 fitting. The spectrum reveals a Si.II.6355 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.