arXiv subjects

Kelly M. Patton

Publications and source records attributed to Kelly M. Patton.

7 recordsLinked to original sources

arXiv2026

The Effect of Mass Loss and Convective Overshooting on the Pre-Collapse Structure, Composition, and Neutrino Emission of Red Supergiants

Prior to core collapse, the neutrino emission from red supergiants (RSGs) is so large that a nearby ($\lesssim$ 1 kpc) RSG will become visible in current and near-future neutrino detectors. The rate of emission and the spectra of the pre-supernova (pre-SN) neutrinos from RSGs are sensitive to the temperature, density, and detailed isotopic composition of the core. During the last year of the star's life, these properties change considerably as the nuclear burning accelerates and deleptonization begins. Uncertainties in stellar evolution modeling, including the treatment of mass loss and convective overshooting, alter the thermal conditions and composition of the RSG core as it approaches collapse, and thus one expects a consequent effect upon the pre-SN emission. In this paper we present the first study of how varying the treatment of mass loss and convective overshooting together affects the pre-collapse core properties and neutrino emission of RSGs, and we also demonstrate that these differences are detectable. We use the stellar evolution instrument MESA and construct a grid of 32 RSG models with zero-age main sequence masses of {12,15,18,20} M$_\odot$, apply the so-called "Dutch" mass-loss scheme with wind efficiencies of {0.2,0.4,0.8,1.0}, and consider two convective overshooting schemes. Our models use a large 206-isotope nuclear network in order to accurately compute the structure and composition of the star. We find that varying the treatment of mass loss and overshooting results in significant differences in core properties and the strength and timing of shell burning episodes, and this translates to observable differences in the pre-supernova neutrino signals.

astro-ph.SR↗

arXiv2020

On Stellar Evolution In A Neutrino Hertzsprung-Russell Diagram

We explore the evolution of a select grid of solar metallicity stellar models from their pre-main sequence phase to near their final fates in a neutrino Hertzsprung-Russell diagram, where the neutrino luminosity replaces the traditional photon luminosity. Using a calibrated \MESA\ solar model for the solar neutrino luminosity ($L_{ν,\odot}$ = 0.02398 $\cdot$ $L_{γ,\odot}$ = 9.1795 $\times$ 10$^{31}$ erg s$^{-1}$) as a normalization, we identify $\simeq$ 0.3 MeV electron neutrino emission from helium burning during the helium flash (peak $L_ν / L_{ν,\odot} \simeq$ 10$^4$, flux $Φ_{ν, {\rm He \ flash}} \simeq$ 170 (10 pc/$d$)$^{2}$ cm$^{-2}$ s$^{-1}$ for a star located at a distance of $d$ parsec, timescale $\simeq$ 3 days) and the thermal pulse (peak $L_ν / L_{ν,\odot} \simeq$ 10$^9$, flux $Φ_{ν, {\rm TP}} \simeq$ 1.7$\times$10$^7$ (10 pc/$d$)$^{2}$ cm$^{-2}$ s$^{-1}$, timescale $\simeq$ 0.1 yr) phases of evolution in low mass stars as potential probes for stellar neutrino astronomy. We also delineate the contribution of neutrinos from nuclear reactions and thermal processes to the total neutrino loss along the stellar tracks in a neutrino Hertzsprung-Russell diagram. We find, broadly but with exceptions, that neutrinos from nuclear reactions dominate whenever hydrogen and helium burn, and that neutrinos from thermal processes dominate otherwise.

astro-ph.SR↗

arXiv2017

Neutrinos from beta processes in a presupernova: probing the isotopic evolution of a massive star

We present a new calculation of the neutrino flux received at Earth from a massive star in the $\sim 24$ hours of evolution prior to its explosion as a supernova (presupernova). Using the stellar evolution code MESA, the neutrino emissivity in each flavor is calculated at many radial zones and time steps. In addition to thermal processes, neutrino production via beta processes is modeled in detail, using a network of 204 isotopes. We find that the total produced $ν_{e}$ flux has a high energy spectrum tail, at $E \gtrsim 3 - 4$ MeV, which is mostly due to decay and electron capture on isotopes with $A = 50 - 60$. In a tentative window of observability of $E \gtrsim 0.5$ MeV and $t < 2$ hours pre-collapse, the contribution of beta processes to the $ν_{e}$ flux is at the level of $\sim90\%$ . For a star at $D=1$ kpc distance, a 17 kt liquid scintillator detector would typically observe several tens of events from a presupernova, of which up to $\sim 30\%$ due to beta processes. These processes dominate the signal at a liquid argon detector, thus greatly enhancing its sensitivity to a presupernova.

astro-ph.HE↗

arXiv2017

Presupernova neutrinos: realistic emissivities from stellar evolution

We present a new calculation of neutrino emissivities and energy spectra from a massive star going through the advanced stages of nuclear burning (presupernova) in the months before becoming a supernova. The contributions from beta decay and electron capture, pair annihilation, plasmon decay, and the photoneutrino process are modeled in detail, using updated tabulated nuclear rates. We also use realistic conditions of temperature, density, electron fraction and nuclear isotopic composition of the star from the state of the art stellar evolution code MESA. Results are presented for a set of progenitor stars with mass between 15 $M_\odot$ and 30 $M_\odot$. It is found that beta processes contribute substantially to the neutrino emissivity above realistic detection thresholds of few MeV, at selected positions and times in the evolution of the star.

astro-ph.SR↗

arXiv2015

Stimulated neutrino transformation through turbulence on a changing density profile and application to supernovae

We apply the model of stimulated neutrino transitions to neutrinos traveling through turbulence on a non-constant density profile. We describe a method to predict the location of large amplitude transitions and demonstrate the effectiveness of this method by comparing to numerical calculations using a model supernova (SN) profile. The important wavelength scales of turbulence, both those that stimulate neutrino transformations and those that suppress them, are presented and discussed. We then examine the effects of changing the parameters of the turbulent spectrum, specifically the root-mean-square amplitude and cutoff wavelength, and show how the stimulated transitions model offers an explanation for the increase in both the amplitude and number of transitions with large amplitude turbulence, as well as a suppression or absence of transitions for long cutoff wavelengths. The method can also be used to predict the location of transitions between antineutrino states which, in the normal hierarchy we are using, will not undergo Mikheev-Smirnov-Wolfenstein (MSW) transitions. Finally, the stimulated neutrino transitions method is applied to the turbulence derived found in a 2D supernova simulation and explains the minimal observed effect on neutrino oscillations in the simulation as as being due to excessive long wavelength modes suppressing transitions and the absence of modes that fulfill the parametric resonance condition.

hep-ph↗

arXiv2014

Stimulated Neutrino Transformation Through Turbulence

We derive an analytical solution for the flavor evolution of a neutrino through a turbulent density profile which is found to accurately predict the amplitude and transition wavelength of numerical solutions on a case-by-case basis. The evolution is seen to strongly depend upon those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. Transitions are strongly enhanced by those Fourier modes in the turbulence which are approximately the same as the splitting between neutrino eigenvalues. We also find a suppression of transitions due to the long wavelength modes when the ratio of their amplitude and the wavenumber is of order, or greater than, the first root of the Bessel function $J_0$.

hep-ph↗

arXiv2013

Stimulated Neutrino Transformation with Sinusoidal Density Profiles

Large amplitude oscillations between the states of a quantum system can be stimulated by sinusoidal external potentials with frequencies that are similar to the energy level splitting of the states or a fraction thereof. Situations when the applied frequency is equal to an integer fraction of the energy level splittings are known as parametric resonances. We investigate this effect for neutrinos both analytically and numerically for the case of arbitrary numbers of neutrino flavors. We look for environments where the effect may be observed and find that supernova are the one realistic possibility due to the necessity of both large densities and large amplitude fluctuations. The comparison of numerical and analytic results of neutrino propagation through a model supernova reveals it is possible to predict the locations and strengths of the stimulated transitions that occur.

hep-ph↗