arXiv subjects

D. Vartanyan

Publications and source records attributed to D. Vartanyan.

2 recordsLinked to original sources

arXiv2026

Mapping 3-D Explosive Nucleosynthesis in Type II Supernova 2024ggi with Infrared Emission Lines

We present analysis and modeling of optical and infrared (IR) spectroscopy of the Type II supernova (SN II) 2024ggi obtained with ground-based instruments and the James Webb Space Telescope (JWST) at phases of ~265 - 400 days. The near- and mid-IR spectra reveal diverse iron-group emission-line morphologies, including double-peaked profiles in [Ni I] 3.119 and 11.998 $μ$m, [Fe II] 1.644 and 17.931 $μ$m, and [Co I] 12.255 $μ$m, alongside Gaussian profiles in [Ni II] 1.939 $μ$m, [Co II] 10.520 $μ$m, and [Ni I] 7.505 and 11.304 $μ$m. These differences imply both chemical inhomogeneity and aspherical ionization of inner ejecta, consistent with expectations from the $^{56}$Ni bubble effect. Modeling of double-peaked profiles supports an ejecta distribution with polar enhancements as large as ~7 for Ni/Co/Fe-rich material and ~2 for intermediate-mass elements. LTE estimates imply a stable Ni mass of $M_{\rm Ni}\approx1.3\times10^{-3}$ M$_{\odot}$, but electron densities near critical values indicate departures from LTE. Comparisons to non-LTE radiative transfer models favor a progenitor mass of ~12 - 15.2 M$_{\odot}$. We show that a simple mapping between elemental mass distribution and projected velocity reproduces line profiles produced in a CMFGEN radiative transfer calculation. We apply this property to 3-D neutrino-driven explosion simulations and predict Ni emission profiles for varying viewing angles. We find that only energetic 3-D explosion models of high-mass progenitors reproduce the observed extent of Ni mixing in SN 2024ggi, conflicting with progenitor masses inferred from radiative transfer models. These results demonstrate the utility of resolved nebular IR lines as direct probes of the 3-D distribution of explosively synthesized material in core-collapse SNe.

astro-ph.HE↗

arXiv2021

Different to the core: the pre-supernova structures of massive single and binary-stripped stars

The majority of massive stars live in binary or multiple systems and will interact during their lifetimes, which helps to explain the observed diversity of core-collapse supernovae. Donor stars in binary systems can lose most of their hydrogen-rich envelopes through mass transfer, which not only affects the surface properties, but also the core structure. However, most calculations of the core-collapse properties of massive stars rely on single-star models. We present a systematic study of the difference between the pre-supernova structures of single stars and stars of the same initial mass (11 - 21\Msun) that have been stripped due to stable post-main sequence mass transfer at solar metallicity. We present the pre-supernova core composition with novel diagrams that give an intuitive representation of the isotope distribution. As shown in previous studies, at the edge of the carbon-oxygen core, the binary-stripped star models contain an extended gradient of carbon, oxygen, and neon. This layer originates from the receding of the convective helium core during core helium burning in binary-stripped stars, which does not occur in single-star models. We find that this same evolutionary phase leads to systematic differences in the final density and nuclear energy generation profiles. Binary-stripped star models have systematically higher total masses of carbon at the moment of core collapse compared to single star models, which likely results in systematically different supernova yields. In about half of our models, the silicon-burning and oxygen-rich layers merge after core silicon burning. We discuss the implications of our findings for the explodability, supernova observations, and nucleosynthesis from these stars. Our models will be publicly available and can be readily used as input for supernova simulations. [Abridged]

astro-ph.SR↗