Exploring the spectral diversity of low-redshift Type Ia supernovae using the Palomar Transient Factory

K. Maguire, M. Sullivan, Y.-C. Pan, A. Gal-Yam, I. M. Hook, D. A. Howell, P. E. Nugent, P. Mazzali, N. Chotard, K. I. Clubb, A. V. Filippenko, M. M. Kasliwal, M. T. Kandrashoff, D. Poznanski, C. M. Saunders, J. M. Silverman, E. Walker, D. Xu

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We present an investigation of the optical spectra of 264 low-redshift(z <0.2) Type Ia supernovae (SNe Ia) discovered by the PalomarTransient Factory, an untargeted transient survey. We focus on velocityand pseudo-equivalent width measurements of the Si II 4130, 5972, and6355 Å lines, as well those of the Ca II near-infrared (NIR)triplet, up to +5 days relative to the SN B-band maximum light. We findthat a high-velocity component of the Ca II NIR triplet is needed toexplain the spectrum in ˜95 per cent of SNe Ia observed before -5days, decreasing to ˜80 per cent at maximum. The average velocityof the Ca II high-velocity component is ˜8500 km s-1higher than the photospheric component. We confirm previous results thatSNe Ia around maximum light with a larger contribution from thehigh-velocity component relative to the photospheric component in theirCa II NIR feature have, on average, broader light curves and lower Ca IINIR photospheric velocities. We find that these relations are driven byboth a stronger high-velocity component and a weaker contribution fromthe photospheric Ca II NIR component in broader light curve SNe Ia. Weidentify the presence of C II in very-early-time SN Ia spectra (before-10 days), finding that >40 per cent of SNe Ia observed at thesephases show signs of unburnt material in their spectra, and that C IIfeatures are more likely to be found in SNe Ia having narrower lightcurves.
Original languageEnglish
Pages (from-to)3258-3274
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date15 Sep 2014
Publication statusPublished - 11 Nov 2014
Externally publishedYes


  • supernovae: general
  • galaxies: general
  • distance scale


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