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

TL;DR

SN 2017cfd is a very typical Type Ia supernova discovered very early, providing valuable early-time data that confirms its normal characteristics and helps constrain its progenitor system.

Contribution

This paper reports the early discovery and detailed analysis of SN 2017cfd, a normal Type Ia supernova, with early multiband data that enhances understanding of early color evolution and progenitor constraints.

Findings

SN 2017cfd is a typical, normal SN Ia with standard luminosity and spectral features.

Early data shows it belongs to the 'blue' color population at early times.

Constraints on the companion star radius suggest no red-giant companion.

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 d after the fitted first-light time (FFLT; 15.2 d 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, Delta m15(B) = 1.16 mag, and reached a B-band maximum ~16.8 d after the FFLT. 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 lambda 6355 velocity of ~11,200 kms at peak brightness. The analysis shows that SN~2017cfd is a very typical, normal SN Ia in nearly every aspect. SN~2017cfd was discovered very young, with multiband data taken starting 2 d after the FFLT, 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_sun, thus ruling out a red-giant companion.