Infant-phase reddening by surface Fe-peak elements in a normal Type Ia Supernova
Abstract
Type Ia Supernovae are thermonuclear explosions of white dwarf stars. They play a central role in the chemical evolution of the Universe and are an important measure of cosmological distances. However, outstanding questions remain about their origins. Despite extensive efforts to obtain natal information from their earliest signals, observations have thus far failed to identify how the majority of them explode. Here, we present infant-phase detections of SN 2018aoz from a brightness of -10.5 absolute AB magnitudes -- the lowest luminosity early Type Ia signals ever detected -- revealing a hitherto unseen plateau in the -band that results in a rapid redward color evolution between 1.0 and 12.4 hours after the estimated epoch of first light. The missing -band flux is best-explained by line-blanket absorption from Fe-peak elements in the outer 1% of the ejected mass. The observed color evolution of the SN also matches the prediction from an over-density of Fe-peak elements in the same outer 1% of the ejected mass, whereas bluer colors are expected from a purely monotonic distribution of Fe-peak elements. The presence of excess nucleosynthetic material in the extreme outer layers of the ejecta points to enhanced surface nuclear burning or extended sub-sonic mixing processes in some normal Type Ia Supernova explosions.
Cite
@article{arxiv.2202.08889,
title = {Infant-phase reddening by surface Fe-peak elements in a normal Type Ia Supernova},
author = {Yuan Qi Ni and Dae-Sik Moon and Maria R. Drout and Abigail Polin and David J. Sand and Santiago Gonzalez-Gaitan and Sang Chul Kim and Youngdae Lee and Hong Soo Park and D. Andrew Howell and Peter E. Nugent and Anthony L. Piro and Peter J. Brown and Lluis Galbany and Jamison Burke and Daichi Hiramatsu and Griffin Hosseinzadeh and Stefano Valenti and Niloufar Afsariardchi and Jennifer E. Andrews and John Antoniadis and Iair Arcavi and Rachael L. Beaton and K. Azalee Bostroem and Raymond G. Carlberg and S. Bradley Cenko and Sang-Mok Cha and Yize Dong and Avishay Gal-Yam and Joshua Haislip and Thomas W. -S. Holoien and Sean D. Johnson and Vladimir Kouprianov and Yongseok Lee and Christopher D. Matzner and Nidia Morrell and Curtis McCully and Giuliano Pignata and Daniel E. Reichart and Jeffrey Rich and Stuart D. Ryder and Nathan Smith and Samuel Wyatt and Sheng Yang},
journal= {arXiv preprint arXiv:2202.08889},
year = {2022}
}
Comments
Accepted for publication in Nature Astronomy. Main text = 8 pages, 4 figures, 1 table; Full document = 46 pages, with Methods, Supplementary Information, 7 Supplementary figures, 2 Supplementary tables and references. Nat Astron (2022)