The Origin and Evolution of the Normal Type Ia SN 2018aoz with Infant-phase Reddening and Excess Emission

Journal Article · 20 March 2023 · The Astrophysical Journal

DOI: https://doi.org/10.3847/1538-4357/aca9be · OSTI ID:2234166

Ni, Yuan Qi  ^[1]; Moon, Dae-Sik ; Drout, Maria R. ; Polin, Abigail ; Sand, David J. ; González-Gaitán, Santiago ; Kim, Sang Chul ; Lee, Youngdae ; Park, Hong Soo ; Howell, D. Andrew ; Nugent, Peter E. ; Piro, Anthony L. ; Brown, Peter J. ; Galbany, Lluís ; Burke, Jamison ; Hiramatsu, Daichi ; Hosseinzadeh, Griffin ; Valenti, Stefano ; Afsariardchi, Niloufar ; Andrews, Jennifer E. ; Antoniadis, John ; Beaton, Rachael L. ; Bostroem, K. Azalee ; Carlberg, Raymond G. ; Cenko, S. Bradley ; Cha, Sang-Mok ; Dong, Yize ; Gal-Yam, Avishay ; Haislip, Joshua ; Holoien, Thomas W.-S. ; Johnson, Sean D. ; Kouprianov, Vladimir ; Lee, Yongseok ; Matzner, Christopher D. ; Morrell, Nidia ; McCully, Curtis ; Pignata, Giuliano ; Reichart, Daniel E. ; Rich, Jeffrey ; Ryder, Stuart D. ; Smith, Nathan ; Wyatt, Samuel ; Yang, Sheng

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1. Univ. of Toronto, ON (Canada); et al.

SN 2018aoz is a Type Ia SN with a B-band plateau and excess emission in infant-phase light curves ≲1 day after the first light, evidencing an over-density of surface iron-peak elements as shown in our previous study. Here, we advance the constraints on the nature and origin of SN 2018aoz based on its evolution until the nebular phase. Near-peak spectroscopic features show that the SN is intermediate between two subtypes of normal Type Ia: core normal and broad line. The excess emission may be attributable to the radioactive decay of surface iron-peak elements as well as the interaction of ejecta with either the binary companion or a small torus of circumstellar material. Nebular-phase limits on Hα and He ι favor a white dwarf companion, consistent with the small companion size constrained by the low early SN luminosity, while the absence of [O ι] and He ι disfavors a violent merger of the progenitor. Of the two main explosion mechanisms proposed to explain the distribution of surface iron-peak elements in SN 2018aoz, the asymmetric Chandrasekhar-mass explosion is less consistent with the progenitor constraints and the observed blueshifts of nebular-phase [Fe ιι] and [Ni ιι]. The helium-shell double-detonation explosion is compatible with the observed lack of C spectral features, but current 1D models are incompatible with the infant-phase excess emission, $$B_{max}$$--$$V_{max}$$ color, and weak strength of nebular-phase [Ca ιι]. Although the explosion processes of SN 2018aoz still need to be more precisely understood, the same processes could produce a significant fraction of Type Ia SNe that appear to be normal after ~1 day.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2234166
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 1 Vol. 946; ISSN 0004-637X
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English