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

abstract

  • 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 H 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 proceedings

  • ASTROPHYSICAL JOURNAL

altmetric score

  • 0.25

author list (cited authors)

  • Ni, Y. Q., Moon, D., Drout, M. R., Polin, A., Sand, D. J., Gonzalez-Gaitan, S., ... Yang, S.

citation count

  • 3

complete list of authors

  • Ni, Yuan Qi||Moon, Dae-Sik||Drout, Maria R||Polin, Abigail||Sand, David J||Gonzalez-Gaitan, Santiago||Kim, Sang Chul||Lee, Youngdae||Park, Hong Soo||Howell, D Andrew||Nugent, Peter E||Piro, Anthony L||Brown, Peter J||Galbany, Lluis||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

publication date

  • March 2023