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

TL;DR

STARLIB is a comprehensive, statistically rigorous nuclear reaction-rate library for astrophysics, providing rates, uncertainties, and probability densities at all temperatures, facilitating improved stellar models and nucleosynthesis simulations.

Contribution

It introduces a novel, statistically defined reaction-rate library with uncertainty distributions, integrating experimental, theoretical, and weak rates for the first time.

Findings

Provides reaction rates with associated uncertainties at all temperatures.

Includes a Monte Carlo formalism for reaction rate calculations.

Enables implementation of probabilistic reaction rates in stellar models.

Abstract

STARLIB is a next-generation, all-purpose nuclear reaction-rate library. For the first time, this 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,g), (p,a), (a,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. We also present a method for accessing STARLIB on the Internet and outline updated Monte Carlo-based rates.