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ABSENCE OF FAST-MOVING IRON IN AN INTERMEDIATE TYPE Ia SUPERNOVA BETWEEN NORMAL AND SUPER-CHANDRASEKHAR

  • Author(s): Cao, Yi
  • Johansson, J
  • Nugent, Peter E
  • Goobar, A
  • Nordin, Jakob
  • Kulkarni, SR
  • Cenko, S Bradley
  • Fox, Ori D
  • Kasliwal, Mansi M
  • Fremling, C
  • Amanullah, R
  • Hsiao, EY
  • Perley, DA
  • Bue, Brian D
  • Masci, Frank J
  • Lee, William H
  • Chotard, Nicolas
  • et al.
Abstract

© 2016. The American Astronomical Society. All rights reserved. In this paper, we report observations of a peculiar SN Ia iPTF13asv (a.k.A., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show an absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band ) and overall spectral features resemble those of normal SNe Ia. On the other hand, its large peak optical and UV luminosity (, ) and its low but almost constant Si ii velocities of about 10,000 km s-1 are similar to those in super-Chandrasekhar events, and its persistent carbon signatures in the spectra are weaker than those seen commonly in super-Chandrasekhar events. We estimate a 56Ni mass of and a total ejecta mass of . The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin.

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