Infant-phase reddening by surface Fe-peak elements in a normal type Ia supernova

Yuan Qi Ni, Dae Sik Moon, Maria R. Drout, Abigail Polin, David J. Sand, Santiago González-Gaitán, Sang Chul Kim, Youngdae Lee, Hong Soo Park, Peter E. Nugent, Anthony L. Piro, Peter J. Brown, Lluís Galbany, Jamison Burke, Daichi Hiramatsu, Griffin Hosseinzadeh, Stefano Valenti, Niloufar Afsariardchi, Jennifer E. Andrews, John AntoniadisIair Arcavi, Rachael L. Beaton, K. Azalee Bostroem, Raymond G. Carlberg, S. Bradley Cenko, Sang Mok Cha, Yize Dong, Avishay Gal-Yam, Joshua Haislip, Thomas W.S. Holoien, Sean D. Johnson, Vladimir Kouprianov, Yongseok Lee, Christopher D. Matzner, Nidia Morrell, Curtis McCully, Giuliano Pignata, Daniel E. Reichart, Jeffrey Rich, Stuart D. Ryder, Nathan Smith, Samuel Wyatt, Sheng Yang

Research output: Contribution to journalArticlepeer-review


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 very low brightness of −10.5 AB absolute magnitude, revealing a hitherto unseen plateau in the B band that results in a rapid redward colour evolution between 1.0 and 12.4 hours after the estimated epoch of first light. The missing B-band flux is best explained by line-blanket absorption from Fe-peak elements in the outer 1% of the ejected mass. The observed B − V colour evolution of the supernova also matches the prediction from an over-density of Fe-peak elements in the same outer 1% of the ejected mass, whereas bluer colours 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 subsonic mixing processes in some normal type Ia SN explosions.

Original languageEnglish
Pages (from-to)568-576
Number of pages9
JournalNature Astronomy
Issue number5
StatePublished - May 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics


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