On Measuring the Metallicity of a Type Ia Supernova’s Progenitor

Abstract

In Type Ia Supernovae (SNe Ia), the relative abundances of chemical elements are affected by the neutron excess in the composition of the progenitor white dwarf. Since these products leave signatures in the spectra near maximum light, spectral features may be used to constrain the composition of the progenitor. We calculate the nucleosynthetic yields for three SN Ia simulations, assuming single degenerate, Chandrasekhar mass progenitors, for a wide range of progenitor metallicities, and calculate synthetic light curves and spectra to explore correlations between progenitor metallicity and the strength of spectral features. We use two 2D simulations of the deflagration-detonation-transition scenario with different 56 Ni yields and the W7 simulation to control for differences between explosion models and total yields. While the overall yields of intermediate mass elements (16 < A ≤ 40) differ between the three cases, trends in the yields are similar. With increasing metallicity, 28 Si yields remain nearly constant, 40 Ca yields decline, and Ti and 54 Fe yields increase. In the synthetic spectra, we identify two features at 30 days post explosion that appear to deepen with progenitor metallicity: a Ti feature around 4200Å and a Fe feature around 5200Å. In all three simulations, their pseudo equivalent widths show a systematic trend with progenitor metallicity. This suggests that these two features may allow differentiation among progenitor metallicities of observed SNe Ia and potentially help reduce the intrinsic Hubble scatter.

Investigating the diversity of Type Ia supernova spectra with the open-source relational data base kaepora

“…It is possible that these weaker Ca features can be explained by differences in progenitor metallicity. The simulations presented in De et al (2014) and Miles et al (2016) show decreasing 40 Ca yields with increasing metallicity while 28 Si yields stay constant. At each phase, our early-type composite spectra show weaker Ca II features than their latetype analogs and Si II features remain roughly constant (especially near maximum light).…”

Fe K and ejecta emission in SNR G15.9+0.2 withXMM-Newton

“…At increasing η, yields of heavy neutron-rich elements (e.g. Mn and Ni) increase, that of Ca and Ar decline, while that of Si remains constant (De et al 2014;Miles et al 2016). The high Ar/Si and Ca/Si observed in SNR G15.9+0.2 could partly be explained by a progenitor with a lower than solar metallicity 11 .…”

The C12(α,γ)O16deBoer1, Görres2, Wiescher3 et al. 2017Rev. Mod. Phys.20081431View full textAdd to dashboardCite

“…Surveys of planetary nebulae find cases of oxygen enrichment by nearly a factor of two relative to carbon (Delgado-Inglada et al, 2015), which may be due to an enhanced 12 C(α, γ) 16 O rate or mixing processes . Asteroseismology studies of white dwarfs seek to determine the 12 C/ 16 O profile and infer the reaction rate from the transition of the white dwarfs inner oxygen-rich region to the carbonrich region in the outer layers (e.g., Metcalfe, 2003).…”

“…The carbon mass fraction impacts the overall energy release, expansion velocity, silicon-group and irongroup ejecta profiles (Calder et al, 2007;Höflich et al, 1998;Miles et al, 2016;Raskin et al, 2012;Röpke et al, 2006;Seitenzahl et al, 2016) in progenitor systems involving either one white dwarf (single degenerate channel) or two white dwarfs (double degenerate channel).…”