Abstract
We present 1D non-local thermodynamic equilibrium (non-LTE) time-dependent radiative-transfer simulations of a Chandrasekhar-mass delayed-detonation model which synthesizes 0.51 Msun of 56Ni, and confront our results to the Type Ia supernova (SN Ia) 2002bo over the first 100 days of its evolution. Assuming only homologous expansion, this same model reproduces the bolometric and multi-band light curves, the secondary near-infrared (NIR) maxima, and the optical and NIR spectra. The chemical stratification of our model qualitatively agrees with previous inferences by Stehle et al., but reveals significant quantitative differences for both iron-group and intermediate-mass elements. We show that +/-0.1 Msun (i.e., +/-20 per cent) variations in 56Ni mass have a modest impact on the bolometric and colour evolution of our model. One notable exception is the U-band, where a larger abundance of iron-group elements results in less opaque ejecta through ionization effects, our model with more 56Ni displaying a higher near-UV flux level. In the NIR range, such variations in 56Ni mass affect the timing of the secondary maxima but not their magnitude, in agreement with observational results. Moreover, the variation in the I, J, and K_s magnitudes is less than 0.1 mag within ~10 days from bolometric maximum, confirming the potential of NIR photometry of SNe Ia for cosmology. Overall, the delayed-detonation mechanism in single Chandrasekhar-mass white dwarf progenitors seems well suited for SN 2002bo and similar SNe Ia displaying a broad Si II 6355 A line. Whatever multidimensional processes are at play during the explosion leading to these events, they must conspire to produce an ejecta comparable to our spherically-symmetric model.
Highlights
The most widely accepted model for Type Ia supernovae (SNe Ia) is the thermonuclear disruption of a white dwarf (WD) star (Hoyle & Fowler 1960) in a binary system, there is ongoing discussion about the combustion mode, the progenitor mass (Chandrasekhar mass or not), and the nature of the binary companion
SN 2002bo was first studied by Benetti et al (2004), who favour a delayed-detonation explosion for this event based on the presence of intermediate-mass elements (IMEs) at high velocities and the lack of spectral signatures of C I/II associated with unburnt carbon at early times
The ±0.1 M variation in 56Ni mass represents a non-negligible variation in the relative abundances of Iron-group elements (IGEs) and IMEs3, which often result in a modest impact on the predicted observables, illustrating the degeneracy of SN Ia properties and the difficulties associated with abundance determinations in these events
Summary
The most widely accepted model for Type Ia supernovae (SNe Ia) is the thermonuclear disruption of a white dwarf (WD) star (Hoyle & Fowler 1960) in a binary system, there is ongoing discussion about the combustion mode (pure deflagration or delayed detonation), the progenitor mass (Chandrasekhar mass or not), and the nature of the binary companion (another WD or a non-degenerate star). We found a promising agreement between a sequence of Chandrasekhar-mass delayed-detonation models and observations of SNe Ia at maximum light (Blondin et al 2013, hereafter B13). A striking feature of SN 2002bo is the large Doppler width of the Si II 6355 Å line around maximum light, which places this SN in the ‘broad-line’ subclass of Branch et al (2006).. A striking feature of SN 2002bo is the large Doppler width of the Si II 6355 Å line around maximum light, which places this SN in the ‘broad-line’ subclass of Branch et al (2006).1 Such a broad Si II line is systematically predicted in maximum-light spectra of the delayed-detonation models presented in B13.
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