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Title: Light curves and spectra from a thermonuclear explosion of a white dwarf merger

Double-degenerate (DD) mergers of carbon–oxygen white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). But, many outstanding questions surround DD mergers, including the characteristics of their light curves and spectra. We have recently identified a spiral instability in the post-merger phase of DD mergers and demonstrated that this instability self-consistently leads to detonation in some cases. We call this the spiral merger SN Ia model. We utilize the SuperNu radiative transfer software to calculate three-dimensional synthetic light curves and spectra of the spiral merger simulation with a system mass of 2.1 $${M}_{\odot }$$ from Kashyap et al. Because of their large system masses, both violent and spiral merger light curves are slowly declining. The spiral merger resembles very slowly declining SNe Ia, including SN 2001ay, and provides a more natural explanation for its observed properties than other SN Ia explosion models. Previous synthetic light curves and spectra of violent DD mergers demonstrate a strong dependence on viewing angle, which is in conflict with observations. Here, we demonstrate that the light curves and spectra of the spiral merger are less sensitive to the viewing angle than violent mergers, in closer agreement with observation. We find that the spatial distribution of 56Ni and IMEs follows a characteristic hourglass shape. Finally, we discuss the implications of the asymmetric distribution of 56Ni for the early-time gamma-ray observations of 56Ni from SN 2014J. We suggest that DD mergers that agree with the light curves and spectra of normal SNe Ia will likely require a lower system mass.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [2] ;  [3] ;  [4] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [6]
  1. Univ. of Chicago, IL (United States). Dept. of Astronomy and Astrophyscis
  2. Univ. of Massachusetts, North Dartmouth, MA (United States). Dept. of Physics
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Polytechnic Univ. of Catalonia, Castelldefels (Spain). Dept. of Physics; Inst. of Space Studies of Catalonia, Barcelona (Spain)
  5. Univ. of California, Santa Barbara, CA (United States). Dept. of Physics
  6. Univ. of Exeter (United Kingdom). School of Physics
Publication Date:
Report Number(s):
LA-UR-15-27535
Journal ID: ISSN 1538-4357
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 827; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE; National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; supernovae; white dwarfs; hydrodynamics; radiative transfer
OSTI Identifier:
1334138