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

Han, Xuhui and Zheng, WeiKang and Stahl, Benjamin E. and Burke, Jamison and Vinkó, József and Cseh, Borbála and Könyves-Tóth, Réka and Krezinger, Máté and Sárneczky, Krisztián and Szakáts, Róbert and Vida, Krisztián (2020) SN 2017cfd: A Normal Type Ia Supernova Discovered Very Young. ASTROPHYSICAL JOURNAL, 892 (2). ISSN 1538-4357

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Abstract

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 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 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.

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