1. The Origin and Evolution of the Normal Type Ia SN 2018aoz with Infant-phase Reddening and Excess Emission
- Author
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Ni, Yuan Qi, 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, and Yang, Sheng
- Subjects
Space Sciences ,Physical Sciences ,Pediatric ,Binary stars ,Supernovae ,Type Ia supernovae ,White dwarf stars ,Transient sources ,Time domain astronomy ,Astronomical and Space Sciences ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Physical Chemistry (incl. Structural) ,Astronomy & Astrophysics ,Astronomical sciences ,Particle and high energy physics ,Space sciences - Abstract
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 i favor a white dwarf companion, consistent with the small companion size constrained by the low early SN luminosity, while the absence of [O i] and He i 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 ii] and [Ni ii]. 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 ii]. 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.
- Published
- 2023