On Variations of Pre-Supernova Model Properties

Abstract

We explore the variation in single star 15-30 M , non-rotating, solar metallicity, pre-supernova MESA models due to changes in the number of isotopes in a fully-coupled nuclear reaction network and adjustments in the mass resolution. Within this two-dimensional plane we quantitatively detail the range of core masses at various stages of evolution, mass locations of the main nuclear burning shells, electron fraction profiles, mass fraction profiles, burning lifetimes, stellar lifetimes, and compactness parameter at core-collapse for models with and without mass loss. Up to carbon burning we generally find mass resolution has a larger impact on the variations than the number of isotopes, while the number of isotopes plays a more significant role in determining the span of the variations for neon, oxygen and silicon burning. Choice of mass resolution dominates the variations in the structure of the intermediate convection zone and secondary convection zone during core and shell hydrogen burning respectively, where we find a minimum mass resolution of ≈0.01 M is necessary to achieve convergence in the helium core mass at the ≈5% level. On the other hand, at the onset of core-collapse we find ≈30% variations in the central electron fraction and mass locations of the main nuclear burning shells, a minimum of ≈127 isotopes is needed to attain convergence of these values at the ≈10% level.

The C12(α,γ)O16deBoer1, Görres2, Wiescher3 et al. 2017Rev. Mod. Phys.20881431View full textAdd to dashboardCite

“…These later evolutionary phases are a rich site of fascinating challenges that include the interplay between nuclear burning (Couch et al, 2015;Farmer et al, 2016;Jones et al, 2017;Müller et al, 2016), convection (Meakin and Arnett, 2007;Viallet et al, 2013), rotation (Chatzopoulos et al, 2016;Heger et al, 2000;Rogers, 2015), radiation transport (Jiang et al, 2015(Jiang et al, , 2016, instabilities (Garaud et al, 2015;Wheeler et al, 2015), mixing (Maeder and Meynet, 2012;Martins et al, 2016), waves (Aerts and Rogers, 2015;Fuller et al, 2015;Rogers et al, 2013), eruptions (Humphreys and Davidson, 1994;Kashi et al, 2016;, and binary partners (Justham et al, 2014;Marchant et al, 2016;Pavlovskii et al, 2017). This bonanza of physical puzzles is closely linked with compact object formation by corecollapse supernovae (e.g., Eldridge and Tout, 2004;Özel et al, 2010;Perego et al, 2015;Sukhbold et al, 2016;Suwa et al, 2015;Timmes et al, 1996) and the diversity of observed massive star transients (e.g., Ofek et al, 2014;Smith et al, 2016;Van Dyk et al, 2000).…”

“…The 15 and 25 M models were calculated from the pre-main sequence to extinction of core He burning, defined as the time when the central mass fraction of He has fallen below 1 × 10 −5 . Other than the specified 12 C(α,γ) 16 O reaction rate, models with the same initial mass assume identical input physics assumptions (e.g., Farmer et al, 2016;Jones et al, 2015). An overview of the model results using the 12 C(α, γ) 16 O reaction rate from this work is given in Table XX. Throughout this section a comparison to the rate from this work is made to that of Kunz et al (2002), as they are propagated through different stellar models.…”

Neutrinos from Beta Processes in a Presupernova: Probing the Isotopic Evolution of a Massive Star

“…The MESA runs used here are the same as those in Farmer et al (2016), where technical details can be found. Each star is modeled as a single, non-rotating, non-mass losing, solar metallicity object.…”

Presupernova Neutrinos: Realistic Emissivities from Stellar Evolution

“…This final instant is defined as t = t c = 0, and all the earlier times t (t < 0) will be defined relative to it, so that −t > 0 will indicate the time-to-collapse. The progenitor models used here are single, non-rotating, non-mass losing stars with a solar metallicity (i.e., mass fraction Z = 0.02 of elements heavier than He) and a solar abundance distribution from Grevesse and Sauval (1998); see Farmer et al (2016) for more details. Note that the range of masses we consider covers some of the diversity expected in the final outcome of the collapse: while the progenitors with lower mass are likely to generate a strong shockwave, resulting in a robust supernova explosion, the heavier ones (M = 25, 30 M ⊙ ) were found to be candidates for direct black hole formation (without explosion, a "failed supernova"), due to their greater compactness (see, e.g.…”

“…We use the models from Farmer et al (2016) with ∆M max = 0.1, where ∆M max specifies the maximum cell mass, and MESA's δ mesh = 1.0, where δ mesh controls the relative variance between cells. The combination of these two settings results in ≈ 1000 − 2000 spatial zones at core collapse.…”