*
Cococubed.com
*

Home

Astronomy research
  Software Infrastructure:
     MESA
     FLASH-X
     STARLIB
     MESA-Web
     starkiller-astro
     My instruments
  White dwarf pulsations:
     12C(α,γ) & overshooting
     Probe of 12C(α,γ)16O
     Impact of 22Ne
     Impact of ν cooling
     Variable white dwarfs
     MC reaction rates
     Micronovae
     Novae
  White dwarf supernova:
     Stable nickel production
     Remnant metallicities
     Colliding white dwarfs
     Merging white dwarfs
     Ignition conditions
     Metallicity effects
     Central density effects
     Detonation density
     Tracer particle burning
     Subsonic burning fronts
     Supersonic fronts
     W7 profiles
  Massive stars:
     Pop III with HST/JWST
     Rotating progenitors
     3D evolution to collapse
     MC reaction rates
     Pre-SN variations
  Massive star supernova:
     Yields of radionuclides
     26Al & 60Fe
     44Ti, 60Co & 56Ni
     SN 1987A light curve
     Constraints on Ni/Fe
     An r-process
     Effects of 12C +12C
  Neutron Stars and Black Holes:
     Black Hole spectrum
     Mass Gap with LVK
     Compact object IMF
     He burn neutron stars
  Neutrino Emission:
     Neutrino emission from stars
     Identifying the Pre-SN
     Neutrino HR diagram
     Pre-SN Beta Processes
     Pre-SN neutrinos
  Stars:
     Hypatia catalog
     SAGB stars
     Nugrid Yields I
     He shell convection
     BBFH at 40 years
     γ-rays within 100 Mpc
     Iron Pseudocarbynes
  Pre-Solar Grains:
     C-rich presolar grains
     SiC Type U/C grains
     Grains from massive stars
     Placing the Sun
     SiC Presolar grains
  Chemical Evolution:
     Radionuclides in 2020s
     Zone models H to Zn
     Mixing ejecta
  Thermodynamics & Networks
     Skye EOS
     Helm EOS
     Five EOSs
     Equations of State
     12C(α,γ)16O Rate
     Proton-rich NSE
     Reaction networks
     Bayesian reaction rates
  Verification Problems:
     Validating an astro code
     Su-Olson
     Cog8
     Mader
     RMTV
     Sedov
     Noh
Software Instruments
AAS Journals
   2024 AAS YouTube
   2024 AAS Peer Review Workshops

2024 ASU Energy in Everyday Life
2024 MESA Classroom
Outreach and Education Materials

Other Stuff:
   Bicycle Adventures
   Illustrations
   Presentations



Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
STARLIB is avaliable at https://starlib.github.io/Rate-Library/



The Impact of Nuclear Reaction Rate Uncertainties On The Evolution of Core-Collapse Supernova Progenitors (2018)

We investigate properties of massive stars with respect to the composite uncertainties in the reaction rates using MESA and STARLIB. This is the first Monte Carlo massive star evolution study that use complete stellar models.



Properties Of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models (2016)

We investigate properties of carbon-oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using MESA and STARLIB. This is the first Monte Carlo stellar evolution study that use complete stellar models.



Bayesian Estimation Of Thermonuclear Reaction Rates (2016)

Estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied in the past to this problem, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extra-solar planets, gravitational waves, and type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. In this article we present astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the d(p,γ)3He, 3He(3He,2p)4He, and 3He(α,γ)7Be reactions, important for deuterium burning, solar neutrinos, and big bang nucleosynthesis.

image image



image



Statistical Methods for Thermonuclear Reaction Rates and Nucleosynthesis Simulations (2015)

Rigorous statistical methods for estimating thermonuclear reaction rates and nucleosynthesis are becoming increasingly established in nuclear astrophysics. The main challenge being faced is that experimental reaction rates are highly complex quantities derived from a multitude of different measured nuclear parameters (e.g., astrophysical S-factors, resonance energies and strengths, particle and γ-ray partial widths). In this article we discuss the application of the Monte Carlo method to two distinct, but related, questions. First, given a set of measured nuclear parameters, how can one best estimate the resulting thermonuclear reaction rates and associated uncertainties? Second, given a set of appropriate reaction rates, how can one best estimate the abundances from nucleosynthesis (i.e., reaction network) calculations?

The techniques described here provide probability density functions that can be used to derive statistically meaningful reaction rates and final abundances for any desired coverage probability. Examples are given for applications to s-process neutron sources, core-collapse supernovae, classical novae, and big bang nucleosynthesis.

image image

image image








STARLIB: A Next-Generation Reaction-Rate Library for Nuclear Astrophysics (2013)

STARLIB, discussed in this article, is a next-generation, all-purpose nuclear reaction-rate library. For the first time, a library provides the rate probability density at all temperature grid points for convenient implementation in models of stellar phenomena. The recommended rate and its associated uncertainties are also included.

Currently, uncertainties are absent from all other rate libraries, and, although estimates have been attempted in previous evaluations and compilations, these are generally not based on rigorous statistical definitions. A common standard for deriving uncertainties is clearly warranted. STARLIB represents a first step in addressing this deficiency by providing a tabular, up-to-date database that supplies not only the rate and its uncertainty but also its distribution. Because a majority of rates are lognormally distributed, this allows the construction of rate probability densities from the columns of STARLIB. This structure is based on a recently suggested Monte Carlo method to calculate reaction rates, where uncertainties are rigorously defined.

In STARLIB, experimental rates are supplemented with: (i) theoretical TALYS rates for reactions for which no experimental input is available, and (ii) laboratory and theoretical weak rates. STARLIB includes all types of reactions of astrophysical interest to Z=83, such as (p,γ), (p,α), (α,n), and corresponding reverse rates. Strong rates account for thermal target excitations. Here, we summarize our Monte Carlo formalism, introduce the library, compare methods of correcting rates for stellar environments, and discuss how to implement our library in Monte Carlo nucleosynthesis studies.

image


image
image


image
image image


 



*   *

* * * *