arXiv subjects

Brandon L. Barker

Publications and source records attributed to Brandon L. Barker.

7 recordsLinked to original sources

arXiv2026

Kilonovae and Long-duration Gamma-ray Bursts

Recent detections of kilonova-like emission following long-duration gamma-ray bursts GRB211211A and GRB230307A have been interpreted as originating from the merger of two neutron stars. In this work, we demonstrate that these observations are also consistent with nucleosynthesis originating from a collapsar scenario. Our model accurately predicts the observed optical and infrared light curves using a single weak $r$-process component. The absence of lanthanide-rich material in our model, consistent with the data, challenges the prevailing interpretation that a red evolution in such transients necessarily indicates the presence of heavy $r$-process elements.

astro-ph.HE↗

arXiv2025

Let there be neutrons! Hadronic photoproduction from a large flux of high-energy photons

We propose that neutrons may be generated in high-energy, high-flux photon environments via photo-induced reactions on pre-existing baryons. These photohadronic interactions are expected to occur in astrophysical jets and surrounding material. Historically, these reactions have been attributed to the production of high-energy cosmic rays and neutrinos. We estimate the photoproduction off of protons in the context of gamma-ray bursts, where it is expected there will be sufficient baryonic material that may be encompassing or entrained in the jet. We show that typical stellar baryonic material, even material completely devoid of neutrons, can become inundated with neutrons in situ via hadronic photoproduction. Consequently, this mechanism provides a means for collapsars and other astrophysical sites containing substantial flux of high-energy photons to be favorable for neutron-capture nucleosynthesis.

astro-ph.HE↗

arXiv2025

Not-Quite-Transcendental Functions For Logarithmic Interpolation of Tabulated Data

From tabulated nuclear and degenerate equations of state to photon and neutrino opacities, to nuclear reaction rates: tabulated data is ubiquitous in computational astrophysics. The dynamic range that must be covered by these tables typically spans many orders of magnitude. Here we present a novel strategy for accurately and performantly interpolating tabulated data that spans these large dynamic ranges. We demonstrate the efficacy of this strategy in tabulated lookups for nuclear and terrestrial equations of state. We show that this strategy is a faster \textit{drop-in} replacement for linear interpolation of logarithmic grids.

physics.comp-ph↗

arXiv2024

Physics-driven Explosions of Stripped High-Mass Stars: Synthetic Light Curves and Spectra of Stripped-Envelope Supernovae with Broad Lightcurves

Stripped-envelope supernovae (SESNe) represent a significant fraction of core-collapse supernovae, arising from massive stars that have shed their hydrogen and, in some cases, helium envelopes. The origins and explosion mechanisms of SESNe remain a topic of active investigation. In this work, we employ radiative-transfer simulations to model the light curves and spectra of a set of explosions of single, solar-metallicity, massive Wolf-Rayet (WR) stars with ejecta masses ranging from 4 to 11 Msun, that were computed from a turbulence-aided and neutrino-driven explosion mechanism. We analyze these synthetic observables to explore the impact of varying ejecta mass and helium content on observable features. We find that the light curve shape of these progenitors with high ejecta masses is consistent with observed SESNe with broad light curves but not the peak luminosities. The commonly used analytic formula based on rising bolometric light curves overestimates the ejecta mass of these high-initial-mass progenitor explosions by a factor up to 2.6. In contrast, the calibrated method by Haynie et al., which relies on late-time decay tails, reduces uncertainties to an average of 20% within the calibrated ejecta mass range.Spectroscopically, the He I 1.083 um line remains prominent even in models with as little as 0.02 Msun of helium. However, the strength of the optical He I lines is not directly proportional to the helium mass but instead depends on a complex interplay of factors such as 56Ni distribution, composition, and radiation field. Thus, producing realistic helium features requires detailed radiative transfer simulations for each new hydrodynamic model.

astro-ph.HE↗

arXiv2023

Inferring Type II-P Supernova Progenitor Masses from Plateau Luminosities

Connecting observations of core-collapse supernova explosions to the properties of their massive star progenitors is a long-sought, and challenging, goal of supernova science. Recently, Barker et al. (2022) presented bolometric light curves for a landscape of progenitors from spherically symmetric neutrino-driven core-collapse supernova (CCSN) simulations using an effective model. They find a tight relationship between the plateau luminosity of the Type II-P CCSN light curve and the terminal iron core mass of the progenitor. Remarkably, this allows us to constrain progenitor properties with photometry alone. We analyze a large observational sample of Type II-P CCSN light curves and estimate a distribution of iron core masses using the relationship of Barker et al 2022. The inferred distribution matches extremely well with the distribution of iron core masses from stellar evolutionary models, and namely, contains high-mass iron cores that suggest contributions from very massive progenitors in the observational data. We use this distribution of iron core masses to infer minimum and maximum mass of progenitors in the observational data. Using Bayesian inference methods to locate optimal initial mass function parameters, we find M$_{\mathrm{min}}=9.8^{+0.37}_{-0.27}$ and M$_{\mathrm{max}}=24.0^{+3.9}_{-1.9}$ solar masses for the observational data.

astro-ph.HE↗

arXiv2022

Connecting the Light Curves of Type IIP Supernovae to the Properties of their Progenitors

Observations of core-collapse supernovae (CCSNe) reveal a wealth of information about the dynamics of the supernova ejecta and its composition but very little direct information about the progenitor. Constraining properties of the progenitor and the explosion requires coupling the observations with a theoretical model of the explosion. Here, we begin with the CCSN simulations of Couch et al 2020 ApJ 890 127, which use a non-parametric treatment of the neutrino transport while also accounting for turbulence and convection. In this work we use the SuperNova Explosion Code to evolve the CCSN hydrodynamics to later times and compute bolometric light curves. Focusing on SNe IIP, we then (1) directly compare the theoretical STIR explosions to observations and (2) assess how properties of the progenitor's core can be estimated from optical photometry in the plateau phase alone. First, the distribution of plateau luminosities (L$_{50}$) and ejecta velocities achieved by our simulations is similar to the observed distributions. Second, we fit our models to the light curves and velocity evolution of some well-observed SNe. Third, we recover well-known correlations, as well as the difficulty of connecting any one SN property to zero-age main sequence mass. Finally, we show that there is a usable, linear correlation between iron core mass and L$_{50}$ such that optical photometry alone of SNe IIP can give us insights into the cores of massive stars. Illustrating this by application to a few SNe, we find iron core masses of 1.3-1.5 solar masses with typical errors of ~0.05 solar masses. Data are publicly available online (\url{https://doi.org/10.5281/zenodo.6631964}).

astro-ph.HE↗

arXiv2020

thornado-hydro: a discontinuous Galerkin method for supernova hydrodynamics with nuclear equations of state

This paper describes algorithms for non-relativistic hydrodynamics in the toolkit for high-order neutrino radiation hydrodynamics (thornado), which is being developed for multiphysics simulations of core-collapse supernovae (CCSNe) and related problems with Runge-Kutta discontinuous Galerkin (RKDG) methods. More specifically, thornado employs a spectral type nodal collocation approximation, and we have extended limiters - a slope limiter to prevent non-physical oscillations and a bound-enforcing limiter to prevent non-physical states - from the standard RKDG framework to be able to accommodate a tabulated nuclear equation of state (EoS). To demonstrate the efficacy of the algorithms with a nuclear EoS, we first present numerical results from basic test problems in idealized settings in one and two spatial dimensions, employing Cartesian, spherical-polar, and cylindrical coordinates. Then, we apply the RKDG method to the problem of adiabatic collapse, shock formation, and shock propagation in spherical symmetry, initiated with a 15 solar mass progenitor. We find that the extended limiters improve the fidelity and robustness of the RKDG method in idealized settings. The bound-enforcing limiter improves robustness of the RKDG method in the adiabatic collapse application, while we find that slope limiting in characteristic fields is vulnerable to structures in the EoS - more specifically, in the phase transition from nuclei and nucleons to bulk nuclear matter. The success of these applications marks an important step toward applying RKDG methods to more realistic CCSN simulations with thornado in the future.

astro-ph.HE↗