Light curves and spectra from a thermonuclear explosion of a white dwarf merger
Van Rossum, DR
American Astronomical Society / IOP Publishing
© 2016. The American Astronomical Society. All rights reserved.
Double-degenerate (DD) mergers of carbon-oxygen white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). However, 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. Here, 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 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. 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.
This work is supported in part at the University of Chicago by the National Science Foundation under grants AST-0909132, PHY-0822648 (JINA, Joint Institute for Nuclear Astrophysics), and PHY–1430152 (JINA-CEE, Joint Institute for Nuclear Astrophysics). This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Simulations at UMass Dartmouth were performed on a computer cluster supported by NSF grant CNS-0959382 and AFOSR DURIP grant FA9550-10-1-0354. The work of E.G.-B., G.A.-S., and P. L.-A. was partially funded by the MINECO AYA2014-59084- P grant and by the AGAUR. This research has made use of NASA’s Astrophysics Data System and the yt astrophysics analysis software suite
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