The most slowly declining type Ia supernova 2001ay

Kevin Krisciunas*, Weidong Li, Thomas Matheson, D. Andrew Howell, Maximilian Stritzinger, Greg Aldering, Perry L. Berlind, M. Calkins, Peter Challis, Ryan Chornock, Alexander Conley, Alexei V. Filippenko, Mohan Ganeshalingam, Lisa Germany, Sergio Gonzlez, Samuel D. Gooding, Eric Hsiao, Daniel Kasen, Robert P. Kirshner, G. H. Howie MarionCesar Muena, Peter E. Nugent, M. Phelps, Mark M. Phillips, Yulei Qiu, Robert Quimby, K. Rines, Jeffrey M. Silverman, Nicholas B. Suntzeff, Rollin C. Thomas, Lifan Wang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We present optical and near-infrared photometry, as well as ground-based optical spectra and Hubble Space Telescope ultraviolet spectra, of the Type Ia supernova (SN) 2001ay. At maximum light the Si II and Mg II lines indicated expansion velocities of 14,000kms-1, while Si III and S II showed velocities of 9000kms-1. There is also evidence for some unburned carbon at 12,000kms-1. SN 2001ay exhibited a decline-rate parameter of Δm 15(B)= 0.68 ± 0.05mag; this and the B-band photometry at t ≳ +25 day past maximum make it the most slowly declining Type Ia SN yet discovered. Three of the four super-Chandrasekhar-mass candidates have decline rates almost as slow as this. After correction for Galactic and host-galaxy extinction, SN 2001ay had MB = -19.19 and MV = -19.17mag at maximum light; thus, it was not overluminous in optical bands. In near-infrared bands it was overluminous only at the 2σ level at most. For a rise time of 18 days (explosion to bolometric maximum) the implied 56Ni yield was (0.58 ± 0.15)/α M, with α = L max/E Ni probably in the range 1.0-1.2. The 56Ni yield is comparable to that of many Type Ia SNe. The "normal" 56Ni yield and the typical peak optical brightness suggest that the very broad optical light curve is explained by the trapping of γ rays in the inner regions.

Original languageEnglish (US)
Article number74
JournalAstronomical Journal
Issue number3
StatePublished - Sep 2011
Externally publishedYes


  • supernovae: individual (SN 2001ay)
  • techniques: photometric
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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