SN 2016iog: A fast declining Type II-L supernova with an ultra-faint tail, persistently interacting with circumstellar material
Authors
Z. -H. Peng
S. Benetti
Y. -Z. Cai
A. Pastorello
G. Valerin
A. Reguitti
A. Fiore
Q. -L. Fang
Z. -Y. Wang
M. Berton
L. Borsato
E. Cappellaro
E. Congiu
N. Elias-Rosa
V. Granata
J. Isern
G. La Mura
P. Ochner
R. Raddi
G. Terreran
L. Tomasella
M. Turatto
S. -Y. Yan
S. -P. Pei
C. -Y. Wu
S. Zha
X. -F. Wang
B. Wang
Y. Pan
Abstract
We present optical photometric and spectroscopic observations of the rapidly declining Type IIL supernova (SN) 2016iog. SN 2016iog reached its peak $\sim$ 14 days after explosion, with an absolute magnitude in the $V$ band of $-18.64 \pm 0.15$ mag, followed by a steep decline of $8.85 \pm 0.15$~mag~(100\,d)$^{-1}$ post-peak. Such a high decline rate makes SN~2016iog one of the fastest declining Type~IIL SNe observed to date. The rapid rise in the light curve, combined with the nearly featureless continuum observed in the spectrum at +9.3 days, suggests the presence of interaction. In the recombination phase, we observed broad H$α$ lines that persist at all epochs. In addition, the prominent double-peaked H$α$ feature observed in the late-time spectrum (+190.8 days) is likely attributable either to significant dust formation within a cool dense shell or to asymmetric circumstellar material. These features suggest the presence of sustained interaction around SN~2016iog. We propose that the observed characteristics of SN~2016iog can be qualitatively explained by assuming a low-mass H-rich envelope surrounding a red supergiant progenitor star with low-density circumstellar material.
